The concept of the Vertebrate Pest Conference originated in early 1960 from discussions among representatives of the University of California; the California Dept. of Fish & Game; the California Dept. of Agriculture; the California Dept. of Public Health; and the Branch of Predator and Rodent Control, Bureau of Sport Fisheries and Wildlife, U.S. Fish & Wildlife Service. The original participants recognized that few published documents on vertebrate pest control were available, as such information was typically contained within in-house reports of the various agencies that were largely unavailable and unable to be cited. Dr. Walter E. "Howdy" Howard of UC realized that having a conference would permit a Proceedings to be published, in which this information could be made widely available.
To plan such a conference, the organizing group, chaired by Dr. Howard, became the Vertebrate Pest Control Technical Committee, which arranged and hosted the first "Vertebrate Pest Control Conference" held in Sacramento on February 6 & 7, 1962. The planning committee formally became an incorporated non-profit entity in 1975, and the Vertebrate Pest Conference is now held in late winter or early spring every two years. It is the most widely-recognized conference of its kind worldwide.
Detailed histories of the development of this Conference are found in these publications:
Volume 22, 2006
Are Viable Non-Lethal Management Tools Available for Reducing Wolf-Human Conflict? Preliminary Results from Field Experiments
Wolf-caused depredation results in substantial economic loss to individual farmers and can lead to greater public animosity towards wolves (i.e., reduction in social tolerance) and the agencies that manage depredations. Using an experimental design in field trials, we are testing shock collars, fladry, and livestock guarding dogs to determine if they are effective in reducing wolf use of areas in Wisconsin and Michigan. During 2003-2004, we equipped 5 wolves with shock collars and found that a 14-day shock period resulted in a decline in wolf use of baited sites by 50% compared to control wolves that increased visitation to baited sites by 18%. During 2005, we found that all pack members in shock-collared wolf packs (n = 5) avoided shock sites for over 60 days after being exposed to a 40-day shock period. During 2004-2005, we found that fladry offered farms at least 90 days of protection from wolves. During 2006-2008, we are conducting field trials with livestock guarding dogs on Michigan farms using an experimental design protocol and additional field trials of shock collars in Wisconsin. Our preliminary data suggest that shock collars and fladry may reduce wolf use of areas within their pack territories. Results of this research will provide important guidelines for implementing potential non-lethal management measures in areas wolves have recolonized or will likely recolonize in the near future and/or where wolves are being reintroduced.
Gray wolf populations were eliminated from the northern Rocky Mountains of the western United States by 1930, largely because of conflicts with livestock. The wolf population is now biologically recovered and over 1,020 wolves are being managed in Montana, Idaho, and Wyoming under the federal Endangered Species Act. From 1987 to December 2005, 528 cattle, 1,318 sheep, 83 dogs, 12 goats, 9 llamas, and 6 horses were confirmed killed by wolves, and over $550,000 was paid from a private damage compensation fund. To help restore the wolf population, we used 22 variations of non-lethal control tools, relocated wolves 117 times, and killed 396 wolves to reduce conflict between wolves and livestock. A variety of tools, including regulations that empower the local public to protect their private property, reduced the probability of wolf-caused damage. This wolf population was restored, the risk of livestock damage reduced, and public tolerance of wolves improved through an integrated program of proactive and reactive non-lethal and lethal control tools. Reduced conflict increases the potential to restore wolf populations.
The management of overabundant native mammals is a contentious issue. In Australia, this is exemplified by the management of kangaroos and koalas. The iconic status of these species, nationally and internationally, greatly influences the perception of acceptable wildlife management practices. Lethal control techniques now face widespread opposition. This has resulted in research and development of alternative management strategies, with emphasis on potential fertility control agents. Australian Research Council Funding in 2005 supported the formation of a new initiative: The Koala and Kangaroo Contraception Program. Over the last 7 years, our research group has been testing the effects of a long-acting contraceptive implant (Suprelorin®, Peptech Animal Health), containing the gonadotropin-releasing hormone (GnRH) agonist deslorelin, on kangaroos and koalas. Within the last year, we have commenced large-scale field trials on two species: koalas on Kangaroo Island, South Australia; and tammar wallabies on the Abrolhos Islands, Western Australia. These field trials aim to evaluate the efficacy of using long-acting contraception to control marsupial populations and will measure the effects of contraception at the individual, population, and environmental level. This is paralleled by development of a remote delivery system that will greatly enhance the efficacy of this form of population management.
Managing an Overabundant Koala Population for Conservation of Riparian Habitats on Kangaroo Island, South Australia
The koala population on Kangaroo Island, South Australia has increased from 18 individuals, released in the 1920s for conservation purposes, to an estimated 27,000 in 2001. The selective browsing pressure of koalas on some eucalypt species, particularly rough-barked manna gum, has resulted in significant detrimental impacts to the riparian habitats of the island. In 1997, a management program was initiated to reduce koala densities and restore damaged habitats. Due to the iconic status of koalas, lethal control measures were rejected in favor of a program based on surgical sterilization and translocation. To date, around 6,000 koalas have been sterilized with around 2,700 of those translocated to suitable habitat in the koala’s former range in southeast South Australia. Although criticized as an expensive approach, the Koala Management Program has resulted in reduced population densities and improved tree condition in areas of intensive management. The Koala Management Program has been adaptive to match improved understanding of koala distribution, population size, and ecology on the island. This paper provides an overview of the koala issue on Kangaroo Island, and the management program implemented to restore damaged riparian habitats.
Conflicts between humans and elephants are escalating in many parts of Africa and displacing elephants from much of their former range. The main causes and effects of these conflicts are outlined and the main management options to address the problem are discussed. For long-term management of human-elephant conflict, site-level interventions alone are unlikely to be sufficient. Action by government agencies, private sector partners, non-governmental organizations and other stakeholders is necessary and should be mutually reinforcing. All the relevant technical, economic, and socio-political issues from the conflict site level to the national level must be addressed to ensure sustainable outcomes for both people and elephants.
Unprovoked attacks by sharks on humans are exceptionally rare phenomena. Sharks typically have two motivations, feeding or defense, that result in attacks on humans. Three species, the bull, tiger, and white sharks, are responsible for the majority of attacks on humans. These predominantly feeding-motivated attacks are often the result of the shark mistaking its human victim for natural prey. Many species, however, exhibit a defensive, aggressive display that, unheeded, may result in a single bite or slashing wound to a human. The number of unprovoked attacks by sharks on humans worldwide has risen from 8 during 1900-1904, of which 2 were fatal, to 330 during 2000-2004, of which 29 were fatal. The rates of 5.8 fatalities per year during 2000-2004 and 6.4 fatalities per year during 1995-1999 are negligible relative to the average of 42,593 fatalities per year due to automobile accidents reported from 1993-1995 in the United States alone. Taking a look at sharks from another perspective, ecotourism has become immensely popular in the 1990s and 2000s. There are opportunities to view sharks in the wild on every continent except Antarctica, with the scalloped hammerhead, white, whale, and reef sharks being among the most popular subjects. Shark ecotourism is providing the public with an observational experience that can be as pleasurable as whale watching, and it can be a cost-effective alternative source of employment for fishermen. This could lead to reduced shark fishing in certain regions of the world and enable shark populations to recover to their former levels of abundance.
Despite the fact that many wildlife species have become overabundant both in North America and other parts of the world, the public is increasingly unwilling to manage wildlife populations with traditional techniques such as trapping or lethal methods. A growing segment of the public is urging the use of contraceptives to reduce populations of overabundant free-ranging wildlife. In spite of public pressure, the development and use of wildlife fertility control techniques has been slow to occur, partially because of the difficulty in developing efficient, cost-effective methods, and partially because of misconceptions about these potential techniques. The regulatory authority for contraceptives has recently been moved from the Food and Drug Administration (FDA) to the Environmental Protection Agency (EPA); the extensive EPA registration process is both rigorous and costly. Only one wildlife contraceptive is currently registered and available: the National Wildlife Research Center (NWRC) worked to develop a product for reducing the hatchability of Canada goose eggs in cooperation with Innolytics, LLC, who holds the registration for OvoControl® G. Development is continuing for additional experimental products. Another product developed by the NWRC, the single-shot GonaCon™ Immunocontraceptive Vaccine is poised to begin the registration process. A third product, DiazaCon™, will be soon tested for field efficacy and should begin the registration process within the year. No single wildlife contraceptive technique would be applicable for use in all wildlife species and for all management situations for a particular species. Differences in animal physiology and behavior, as well as differences in the ecology of the damage, affect which contraceptives will be most effective. Therefore, contraceptives with different modes of action will need to be developed for different species and uses. Wildlife contraceptives will not replace other management tools and will probably have a limited use, primarily in urban/suburban areas. In most species, wildlife contraceptives will not rapidly reduce populations. Populations of short-lived species such as rodents could be rapidly reduced with contraceptives; however, in long-lived species such as deer and horses, it would take years to reduce populations with fertility control alone, and damage caused by those species will continue to occur. This manuscript will discuss what contraceptive techniques are being developed by the USDA Wildlife Services NWRC, and when, where, and for what species they may be applicable.
A Modeling Approach to Evaluating Potential Applications of Emerging Fertility Control Technologies in the UK
There is increasing demand for benign approaches to the resolution of conflicts between human interests and wildlife. One non-lethal method to reduce the growth and expansion of overabundant wildlife populations is fertility control. Significant progress has been made in recent years on the development of fertility control agents, culminating in the availability of single-dose injectable immunocontraceptive vaccines that inhibit the fertility of individuals for several years. The potential application of such technology is explored here using the European rabbit, gray squirrel, wild boar, and European badger as examples of species that pose problems of damage to agricultural and forestry interests, disease transmission and threats to biodiversity. A simple model is developed that predicts the likely general population consequences of varying levels of infertility for species with differing demographic characteristics. This suggests that low levels of fertility control will have little impact on population size in species with high reproductive rates and high population turnover rates. Modest levels of infertility can significantly reduce the populations of species with relatively low intrinsic rates of increase. However, these reductions may take longer than those arising from high levels of imposed infertility in species with rapid population turnover rates. The modeling approach, as outlined here, could be used to inform future field studies by identifying suitable target species and making predictions about population responses that can be tested empirically. These studies will be necessary to realize the potential of the emerging fertility control technologies in the form of practical wildlife management applications.
Changing cultural values and increasing urbanization in the United States are curtailing traditional wildlife management tools used to effectively manage conflicts between human and wildlife populations. Because of this trend, the USDA Wildlife Services, National Wildlife Research Center (NWRC) began developing wildlife contraceptives in 1991. Since that time, NWRC scientists have steadily worked toward the goal of developing and registering contraceptive products that are practical to use, safe for the treated animal, and present little risk to humans, nontarget animals, and the environment. Working cooperatively with Innolytics, LLC, OvoControl G™ was recently registered for reducing the hatchability of Canada goose eggs. Another product developed by the NWRC, the single-shot GonaCon™ Immunocontraceptive Vaccine is poised to begin the registration process. A third product, DiazaCon™, soon will be tested for field efficacy and should begin the registration process within the year. Between 1996 and the present, the regulatory agency responsible for wildlife contraceptives has been the Food and Drug Administration, Center for Veterinary Medicine (CVM). Working under this premise, the NWRC has progressed toward fulfilling CVM’s regulatory requirements by conducting field efficacy studies and a target animal safety study. NWRC explored various registration options with the CVM, and also with the USDA APHIS Center for Veterinary Biologics (CVB). Through this process, it became clear that wildlife contraceptives were incompatible with CVM’s regulatory process, and outside the regulatory authority of CVB. In response, CVM and the U.S. Environmental Protection Agency (EPA) negotiated an agreement on contraceptive uses. The EPA will assume regulatory authority of contraceptives used for wildlife and feral animals. The CVM will retain authority over all uses in captive animals including livestock, companion animals, and zoo animals.
Controlling fertility of feral horses through the use of long-acting contraceptives or sterilization approaches has been championed as a reasonable and humane solution for addressing overpopulation problems in several western states. However, methods to accomplish long-term contraceptive efficacy of horses following a single treatment have been lacking. In fall 2002 and spring 2003, we initiated a study to compare the long-term efficacy of a single-shot contraceptive vaccine directed at gonadotropin releasing hormone (GonaCon™) to that of a single-shot vaccine directed at the zona pellucida (SpayVac) and to the use of intrauterine contraceptive devices (IUD). Both vaccines were administered with AdjuVac™, an adjuvant developed at the National Wildlife Research Center. The objectives of the study were to determine: 1) 3-year efficacy for preventing pregnancy, 2) whether the contraceptive effects are reversible, and 3) whether there are contraindications. The Nevada Department of Agriculture provided the feral mares, which were maintained at the Nevada State Penitentiary, Carson City, facility. Mares were dewormed and given health vaccinations annually. Eight untreated control mares were compared to 12 mares treated with SpayVac, 16 mares treated with GonaCon™, and 15 mares treated with copper-containing IUDs. Only 25% (2/8) of the control mares were not pregnant or infertile in the first year. All mares in the SpayVac group were infertile, and 94% (15/16) were infertile in the GonaCon™ group during the first breeding season. In Year 2, 80% (10/12) of the SpayVac-treated mares and 60% (9/15) of the GonaCon™-treated mares were infertile. In Year 3, 80% of the SpayVac mares and 53% (8/15) of the GonaCon™-treated mares were infertile. For IUD-treated mares, 80% (12/15) were infertile after Year 1, but only 29% (4/14) and 14% (2/14) were infertile after Years 2 and 3, respectively. For IUD mares that were infertile, it was possible to visualize the IUD by ultrasonography, leading us to conclude that mares that became pregnant had lost their IUDs. For mares given SpayVac, uterine edema was commonly observed. In Years 2 and 3, antibody titers for SpayVac were progressively lower compared to titers observed in Year 1.
High deer densities increase vehicle collisions, damage agricultural crops, and amplify the spread of zoonotic and animal diseases, intensifying human-deer conflict. In addition, deer impact on forest vegetation can influence the distribution and abundance of other wildlife species. Greater demand for non-lethal means of animal damage control has led to an interest in contraception as a wildlife management tool. The development of a single-injection Gonadotropin-Releasing Hormone (GnRH) contraceptive vaccine by NWRC reduces logistical limitations and cost of using immunocontraception as compared to a vaccine that requires two injections. This study assessed the efficacy of two different GnRH-KLH (keyhole limpet hemocyanin) vaccine designs in a single-injection study, to determine if Mycobacterium avium bacterium in the adjuvant is necessary for the success of a single-injection contraceptive vaccine. Forty-two captive female black-tailed deer were divided into 3 groups. Control deer were injected with saline solution, one treatment group received GonaCon™ (a GnRH-KLH vaccine paired with AdjuVac™ adjuvant that contains a small quantity of killed M. avium bacterium), and the second treatment group received GnRH-KLH vaccine with DEAE-Dextran/oil as the adjuvant. Contraceptive success was evaluated by monitoring progesterone, pregnancy specific protein, antibodies to GnRH-KLH conjugate and to Johne’s bacterium (M. avium), and actual pregnancy rates. Pregnancy rates were significantly different based on treatment (X² = 9.389; df = 2; P = 0.009). Pregnancy rates in deer treated with GonaCon™ were significantly reduced as compared to saline controls (P = 0.006), but there was no significant difference between GnRH-DD compared to saline (P = 0.297). Significant difference was found between GonaCon™ and GnRH-DD (P = 0.055). Results suggest that M. avium in the AdjuVac™ adjuvant is essential for the success of the single-injection GnRH vaccine GonaCon™. The development of a single-injection vaccine will increase the practicality and lower the cost of using immunocontraception as a tool to control deer populations.
Locally overabundant deer herds, particularly those inhabiting fenced or other enclosed areas in urban or suburban settings, are presenting serious problems for wildlife managers, landowners, and the general public. Traditional methods of population control, such as regulated harvest by licensed hunters, often are impractical or illegal in such settings. The development of safe and effective wildlife contraceptives is needed to control locally overabundant populations in situations where traditional management tools cannot be employed. During July 2004, we initiated a field study of GonaCon™ Immunocontraceptive Vaccine, developed by research scientists at the National Wildlife Research Center in Fort Collins, Colorado. This vaccine had previously been tested successfully as a contraceptive in captive animals including white-tailed deer, feral and domestic swine, and wild horses. The two-year field study was prompted by the need to manage an enclosed, overabundant population of white-tailed deer that had caused considerable ecological damage to a 662-acre, federally-owned, forested site in Silver Spring, Maryland. The U.S. General Services Administration, which manages the property, conducted an environmental assessment, which concluded that sharpshooting followed by immunocontraception would be the most appropriate deer management strategy. After 214 deer were removed from the site by sharpshooters, we set up and tested an automated radio telemetry system for tracking deer and monitoring their mortality. Twenty-eight does were then captured, equipped with ear tags and radio telemetry collars, and injected with GonaCon™ vaccine. Fifteen additional does were captured, marked, and released without vaccination as untreated control animals. Reproductive behavior and fawn production by the vaccinated and unvaccinated does will be monitored and compared for two years, and will be used to determine the efficacy of GonaCon™ as a wildlife contraceptive agent. Data from this study will be used to support EPA registration of GonaCon™ as a wildlife contraceptive agent.
GonaCon™ Immunocontraceptive Vaccine targets the reproductive hormone gonadotropin releasing hormone (GnRH) secreted by the hypothalamus of the brain. Antibodies produced in response to the vaccine inactivate endogenous GnRH, which in turn eliminates stimulation of the pituitary gland and gonads in males or females. The resulting “immunocastration” renders animals unable to produce reproductive steroids or gametes. In previous studies, we demonstrated that GonaCon™ was effective in impairing fertility for up to 3 years in female deer without apparent side effects. However, detailed post mortem evaluations were not done. To better understand the entire physiological response of deer to GonCon™ and to establish if contraindications were associated with its use, we undertook the present study. To evaluate toxicity and safety, 7 does were given the standard single injection GnRH-KLH vaccine dose (1000 µg) delivered IM in 1 ml using AdjuVac™ adjuvant and compared to 6 does given a single control saline IM injection and 6 does given 3 injections of GonaCon™ at 2-week intervals per dose. The study was conducted for 20 weeks. Does were blocked by weight and randomly assigned within blocks to treatment groups. Blood samples were drawn immediately prior to vaccination and at 5, 10, 15, and 20 weeks post immunization. Blood was assayed for LH, testosterone and progesterone, and anti-GnRH titers, as well as hematology and blood chemistry. At each sampling period, the general health of the doe was observed and the injection site was inspected for the formation of abscesses or other tissue reactions. At Week 20, all deer were euthanized and evaluated at necropsy by veterinary pathologists and samples of lymph nodes, reproductive organs, lung, liver, heart, kidney, spleen, and brain were taken for histology. Aside from granulomata formation at the injection site, there were no significant contraindications or toxic effects associated with GonaCon™.
The use of poisons for coyote control is controversial because of public opposition to lethal control of pest animals and the perceived environmental risks of pesticide use. The development of immunocontraception for population control of coyotes could result in a more acceptable alternative to poisons. Immunocontraception using porcine zona pellucida (PZP) would allow normal estrus in the female and therefore normal male-female pair-bonding. Coyotes are mon-estrus, therefore PZP contraception during the breeding season of February and March could provide year-round protection. This paper reviews 9 years of research on PZP immunocontraception, starting from a multi-shot PZP vaccine using Freund’s adjuvant, to the development and testing of two single-shot preparations combined with a newly developed adjuvant (AdjuVac™). We provide insights into the false assumption that one contraceptive vaccine fits all species and situations.
Many exotic vertebrate species have been introduced either accidentally or intentionally into the Australian environment. Native species have also become pests due to changes in landscape use. Management of these pest populations, whether introduced or indigenous, is of concern both nationally and internationally. Public approval of existing pest control techniques involving lethal agents (poisoning, shooting, trapping, or disease) has declined in favour of alternative techniques, which are more humane, cost effective, species-specific, environmentally friendly, and suitable for delivery on a continental scale. Population management through disruption of reproduction rather than through the use of mortality agents has gained acceptance in the past 10-15 years. This has led to considerable research into the development of immunocontraceptive agents, for example to prevent mouse populations irrupting to plague proportions in cereal-growing regions of Australia. We have examined whether mouse populations can be managed with fertility control delivered using a transmissible mouse-specific virus (mouse cytomegalovirus, MCMV), engineered to carry an infertility agent. Field and laboratory results, as well as computer modelling, show excellent prospects for the use of vaccines based on MCMV. However, the efficiency of transmission of infertility remains a major challenge for the current research program. The public acceptability of the technology is yet to be confirmed. The issues of species specificity, delivery system stability, transmission efficiency, and other potential or perceived risks require open and wide-ranging debate, nationally and internationally, before trial field experiments of a genetically modified virus for controlling field populations of mammals could occur.
Fertility control vaccines are under development for a number of pest wildlife species, mostly based on whole zona pellucida (ZP) or individual ZP proteins. Such vaccines must be effective, long lasting, cheap and readily deployed. One approach to deployment is oral delivery in baits. This is one strategy being taken in New Zealand for control of brushtail possums, 2- to 4-kg marsupials introduced from Australia in the 1850s, and now major pests of both conservation and agricultural production. New Zealand has highly effective aerial and ground systems for delivery of toxic baits to possums that could be adapted readily to deliver vaccine baits. Recent trials in captivity where female possums were immunised with recombinant possum ZP3 and ZP2 proteins demonstrated 70-75% reductions in fertility in natural and assisted breeding trials. Immunisation with possum-specific epitopes of the ZP2 and ZP3 proteins has also proved effective at reducing the numbers of fertilised eggs recovered from immunised females. For field delivery of an oral vaccine, we are investigating the use of bacterial “ghosts”. These are the empty cell walls of bacteria that have been modified to express possum ZP proteins in their cell walls. The possum’s immune system recognises the bacterial ghost as foreign, and produces antibodies against them. At the same time, it is tricked into developing antibodies against the possum egg proteins, causing a contraceptive effect. In a recent proof of concept trial, female possums immunised with a possum ZP2-bacterial ghost vaccine by nasal spray showed a significant reduction in fertility. Oral delivery may require protection of vaccine ghosts from degradation. We have developed a protective system and are currently repeating this trial using oral delivery of the ZP2 ghost vaccine. Our future priority is increasing the vaccine efficacy and longevity ahead of limited field trials in 2009.
GonaCon™ is a gonadotropin releasing hormone (GnRH) contraceptive vaccine developed at the USDA National Wildlife Research Center (NWRC) that contains keyhole limpet hemocyanin (KLH) coupled to GnRH. The vaccine is administered intramuscularly in an emulsion with the NWRC adjuvant, AdjuVac™. This first-generation vaccine, developed in 1998, has been very effective in contracepting every species tested. However, because of the high cost of KLH, NWRC has developed a second generation GnRH vaccine, replacing KLH with a less expensive mollusk protein. This second generation GnRH vaccine, called GonaCon-Blue™, is currently being tested in several species and has proven to be as, or more effective than the original GonaCon™. Scientists with the Reproductive Control Methods Project at the NWRC are also testing a recombinant GnRH antigen developed by Dr. Talwar of the Talwar Research Institute, India. The recombinant antigen was produced from plasmid gene expression grown in and extracted from E. coli. The antigen is combined with the NWRC AdjuVac™ to form an emulsion similar to the GonaCon™ preparation. The recombinant vaccine has been shown to be effective as a single or dual injection for contraception of adult female pigs in a short-term study at the Swine Research Facility at Penn State University. Although the long term effectiveness of the recombinant vaccine remains to be established, this small molecule of approximately 14,000 MW is of considerable interest because it may be effective in oral or transcutaneous applications. It could also be scaled-up for large field applications.
Avian contraception is a nonlethal management tool that can be utilized in conjunction with other management techniques to help manage bird populations causing damage. Because management situations vary with respect to the type of damage, species involved, location, and nontarget hazards, it is necessary to develop multiple contraceptive tools to allow management flexibility. DiazaCon™ and nicarbazin have already been developed at the National Wildlife Research Center as avian contraceptives. Although both of these are promising contraceptive agents, more are needed for a wider variety of situations. Current research is focusing on other cholesterol inhibitors, inhibitors of the P450 side chain cleavage enzyme, and aromatase inhibitors. Because cholesterol is needed for steroid reproductive hormone production, inhibition of cholesterol impairs reproduction by preventing the formation of the necessary hormones. The P450 side chain cleavage enzyme is needed to convert cholesterol to pregnenolone, the precursor to progesterone and testosterone. Progesterone is needed for egg formation, ovulation, and oviposition, and testosterone is needed for sperm production. Aromatase is needed to convert testosterone to estradiol, which is needed in females to stimulate the production of egg yolk precursors in the liver. Inhibition of either of these enzymes should result in impaired reproduction. In the future, natural plant products with contraceptive activity, such as neem seed, will also be investigated. Because development of avian contraceptives is time intensive, an efficient screening process needs to be in place. Population models can assist in choosing specific agents to test for a given species and management situation. Although contraception is unlikely to be useful as a stand-alone tool, it can be included in integrated management plans.
Effective methods for managing populations of rock pigeons and other overabundant avian species are limited. An alternative to lethal control is reproductive inhibition. Nicarbazin is a widely used additive in poultry feed that also reduces hatchability of eggs. It is the active ingredient in OvoControl®G, a bait product recently registered as a means for reducing hatchability of eggs of urban Canada geese. In a series of trials with captive pigeons, we evaluated the effectiveness of several nicarbazin bait formulations to determine effects on reproduction and to quantify levels of nicarbazin absorbed into the blood. Although pigeons readily accepted a scaled-down version of the OvoControl goose bait, this formulation did not adequately reduce hatchability because of insufficient absorption of nicarbazin into the blood. Other bait formulations that contained 2,500 ppm nicarbazin produced similar results. Only bait formulated with 5,000 ppm nicarbazin produced sufficient amounts of the active ingredient in blood plasma of test birds. Eventual registration of the nicarbazin pigeon bait will provide additional management options for limiting growth of unwanted pigeon populations.
Controlling reproduction is a responsibility facing both zoo and wildlife managers, and contraception is one of their options. However, management goals and parameters affecting administration of contraceptives vary considerably for free-ranging and captive wildlife. Captive breeding programs consider the entire captive population but manage at the level of the individual. Not only must they focus on the genetic value of individual animals, but each birth results in an animal that will require resources and occupy limited space for its lifetime. Thus, captive programs dictate that contraceptive be virtually 100% effective, safe, and reversible. This contrasts with management of most free-ranging animals, where reproductive rate of the population, not each individual, is the measure of success. The other notable distinction is ease of delivery in captive populations, perhaps the greatest challenge with free-ranging animals. Captive animals are always accessible, are individually known, and can be monitored. Yet, despite these differences, zoo and wildlife biologists can benefit from collaborative efforts, especially when they target the same species. In particular, trials with captive animals can provide more definitive results than comparable studies with free-ranging animals. In addition, we all face the problems inherent in programs that represent a limited commercial market. Improved communication and exploring the potential for collaborations may accelerate our progress.
The house mouse is probably the most widespread invasive mammalian species, being ubiquitous worldwide. In commensal situations, they are known mainly for property damage, for consumption and contamination of stored foods, as a noise/sanitation/odor nuisance, and as a vector of some diseases. In some field settings, they also cause considerable damage to field crops and to natural resources, such as when introduced to islands. We rely heavily upon sanitation, rodent-proofing, capture devices, and rodenticides to control populations and reduce damage. However, a number of situations exist whereby these traditional methods are not adequate or appropriate: crop damage during “mouse plagues” in Australia, livestock feed consumption and contamination and disease hazards in poultry and animal facilities in the U.S., and natural resource damage on small islands. In this review, challenges and some potential solutions to house mouse management are presented, including genetic resistance to anticoagulants, the effectiveness of baits given abundant food resources, the re-invasion problem and need for perimeter strategies, efforts with fertility control, and the need for effective multi-capture trap devices. In difficult situations, an IPM strategy that incorporates a combination of methods closely integrated with land uses and management practices is necessary.
A Profile of the Norway rat, Rattus norvegicus, in New York City: Its Impact on City Operations and the Need for Collaborative Interagency Rat Management Programs
New York City, New York is a uniquely ideal urban habitat for the Norway rat. There are several reasons for this, but foremost is New York’s being one of America’s oldest seaport cities and the most densely populated city in the U.S., with a population of at least 8.2 million residents, all living within only a 321-square-mile area. Thus, food resources are readily abundant and easily accessible to rats. So, too, is an abundance of rat harborage resources, ranging from earthen burrows, to a myriad of subterranean harborages within city infrastructures, to the structural harborages associated with the city’s buildings numbering in the millions. Such conditions allow the opportunistic brown rat to proliferate, spread, and repeatedly rebound from extermination campaigns that have been directed at it for over a 200-year period. This paper presents a profile of the brown rat as a major urban pest of New York City and its impact within the context of New York’s daily operations. An overview is presented of the City of New York’s infrastructure and city management agencies of most relevance in rat management programs, and of the city’s collaborative interagency approaches.
Grower Evaluation of California Ground Squirrel (Spermophilus beecheyi) Control using Anticoagulant Baits
California ground squirrels continue to present a significant problem for many facets of California agriculture. The use of diphacinone- and chlorophacinone-treated baits remains the most frequent control method for ground squirrels in agricultural settings. Research suggests no difference in efficacy between the two bait types or between broadcast and spot baiting strategies or bait stations. However, these studies were limited in scope and were conducted exclusively on rangeland sites where there is limited availability of alternate food sources. Studies also suggest that a reduced baiting strategy may be as effective as current label recommendations, but this has received only limited attention in field research. We utilized a new approach in conducting field evaluations of anticoagulant baiting efficacy in different agricultural settings and locations throughout the state. We solicited agricultural producers as cooperators to participate in a field-based evaluation to determine if the reduced baiting strategies are effective under specific agricultural operating conditions. Cooperators were trained in a simple research design and monitored to ensure consistent data collection. The training program included a comprehensive manual on squirrel biology, behavior, and control, as well as information on toxicants and legal measures regarding endangered species. An informal survey was sent to cooperators at the end of the project to evaluate their opinions on the efficacy of control methods. We found no difference in efficacy between baiting methods or strategies. Differences in efficacy were found between chlorophacinone and diphacinone and efficacy was lower in nut orchards than in other settings. Despite no difference in efficacy between baiting methods, more cooperators indicated they would use bait stations than other methods in future ground squirrel control operations.
Evaluation of Irrigation Valve Boxes as Underground Bait Stations for California Ground Squirrel Control
The anticoagulants chlorophacinone and diphacinone are registered in California to control ground squirrels. Since multiple feedings on these anticoagulants are necessary, bait stations are often used. Several bait station designs have been suggested and used to reduce tampering and also to minimize bait exposure to non-target animals. Potential options to reduced exposure risk strategies are to use a modified-T bait station, underground bait station, or in-burrow baiting. This study evaluated the behavior of ground squirrels with regard to modified-T and underground bait station compared to the standard-T bait station that is commonly used for ground squirrel control.
Efficacy of Strychnine and Zinc Phosphide Cabbage Baits in Controlling Ground Squirrels in Diamond Valley, Nevada
A field trial was conducted to determine the efficacy of strychnine and zinc phosphide cabbage baits for controlling ground squirrels in Diamond Valley, Nevada. The reduction in aboveground ground squirrel activity was 83% for strychnine and 70% for zinc phosphide. Similar results were found for reductions in burrow activity: 88% for strychnine and 70% for zinc phosphide. Strychnine appeared to be slightly more effective than zinc phosphide, but both appeared to be effective for ground squirrel control.
The California meadow vole, Microtus californicus, is a major vertebrate pest in artichoke fields of Castroville, California. Complaints from growers about the effectiveness of the only available rodenticide, chlorophacinone treated artichoke bracts, led researchers to the test the bait and baiting strategies. When laboratory trials were conducted in 2001, the poor dose-response correlation and apparent low sensitivity to chlorophacinone in some animals suggested the possibility of anticoagulant resistance. The current study was initiated to examine potential resistant of voles from artichoke fields in the Castroville area. Baseline blood coagulation data were obtained from wild, anticoagulant-susceptible voles trapped in Yolo County, California and compared to data from Castroville voles. Results indicate a significant difference in clotting times 24 hours after dosing with anticoagulant between voles from Castroville artichoke fields and voles from the Yolo population. This supports the hypothesis that voles from Castroville artichoke fields are resistant to anticoagulants.
Zinc Phosphide-Treated Bracts as an Alternative Rodenticide in Artichoke Fields for Meadow Vole (Microtus californicus) Control
Artichoke growers in Monterey County, California currently use a fresh artichoke bract chlorophacinone bait to control their primary vertebrate pest, the California meadow vole. Upon suspected chlorophacinone resistance by meadow voles in artichoke fields, an alternative has been sought. We studied the effect of zinc phosphide-treated artichoke bracts on California meadow voles. We found that zinc phosphide-treated artichoke bracts were effective in reducing meadow vole populations on treated plots by 95-98%. Our results suggest that zinc phosphide-treated artichoke bracts are effective in reducing California meadow vole populations in artichoke fields and may provide a useful alternative for areas in which anticoagulant resistance by voles is suspected.
Efficacy of Cholecalciferol Baits for Pocket Gopher Control and Possible Effects on Non-Target Rodents in Pacific Northwest Forests
Population reduction measures need to be implemented to reforestation plots infested with pocket gopher in the Pacific Northwest. This 1-year investigation assessed the efficacy of 0.15% cholecalciferol (vitamin D3) bait application to reduce pocket gophers and the long-term effects on non-target small rodent populations within treated plots. The study site was a reforested clear cut containing pocket gopher populations of 10 to 14 animals per ha. Six plots (2.8 ha each) were randomly selected at the study site, 3 plots of untreated controls and 3 plots baited with cholecalciferol. A trap-and-release program was used to assess non-target populations. Radio telemetry and the open hole method were used to monitor pocket gopher activity before and after the fall application of cholecalciferol bait. A 70-80% reduction of pocket gopher activity from telemetered animals occurred in the treated plots, whereas only 10-20% mortality occurred on the control plots. Pocket gopher activity in most of the plots increased by June, and by September of the following year, activity was back to original levels. Time, not treatment, had a significant effect on yellow pine chipmunk, Townsend chipmunk, and golden-mantled ground squirrel populations. We conclude that 0.15% cholecalciferol bait appears to have application for pocket gopher control. Risks to non-target species may exist.
The Bailey beaver trap is a suitcase-type beaver trap manufactured by the Tomahawk Live Trap Company. Although an effective tool in capturing beaver, it is known for its high misfire rate. This paper explains and expands upon Richard Buech’s tips for modifying and employing the Bailey beaver trap, which can reduce the misfire rate by 50%.
Once extirpated from large parts of this country, the beaver has made a surprising comeback. However, the beaver’s return to its former range is accompanied by a rising number of complaints caused by beaver-created impoundments. Highway departments, homeowners, and government officials find themselves confronting costly damage to septic systems, road infrastructures, and property as a result of the beaver’s engineering ingenuity. The traditional response has been to trap and remove beavers, yet this solution is often short-term due to the continual immigration of beavers from the surrounding habitat. In addition, public attitude surveys reflect a growing desire for more humane solutions and rank animal suffering as a major determinant of which wildlife management practices are considered acceptable. To meet this growing need, two entities, The Humane Society of the United States and Beaver Solutions, Inc., established their own respective programs to help communities and homeowners resolve beaver problems through the use of water flow control devices (WFCDs), which present a relatively new, little known yet innovative concept. WFCDs are designed to control the water level, thereby preventing flooding, while allowing the beavers to remain in their habitat. This paper describes the social and ecological context for current beaver problems, how WFCDs function, gives installation and maintenance tips, and presents results of two surveys that assessed the effectiveness of WFCDs in alleviating beaver flooding problems in Connecticut and Massachusetts.
Mountain beaver are a primitive rodent species endemic to the Pacific Northwest and California. In Oregon and Washington, mountain beaver are managed as a pest species due to the damage they inflict to Douglas-fir seedlings as well as 10- to 15-year-old trees. Available biological information on the mountain beaver is limited, thus hampering the ability of managers to develop new tools and techniques to reduce damage. We conducted a series of studies to increase our knowledge of mountain beaver biology and the influence of environmental attributes and stand management practices on demographics. Although mountain beaver damage Douglas-fir and western red cedar seedlings, observations suggest that these tree species are not preferred forage. In one pen study, pens void of preferred vegetation (i.e., salal and sword fern) had significantly more damage than pens with additional forage. Damage did not occur when animals were allowed access to pens with preferred forage, even with increased population pressure. In addition to pen trials, we radio-collared 62 mountain beaver in 3 different harvest units, which varied in vegetation management and stand age, to assess movements and seedling damage. Home ranges were larger on the chemically prepared site with reduced forage than on the non-treated site. Although mountain beaver can inhabit older timber stands, home ranges were relatively large in such stands because of the reduced preferred forage in closed-canopy habitats (3.66 ± 1.49 ha). Once units were harvested, population size increased and home range size decreased (0.88 ± 0.27 ha). Seedling damage and reproductive success were only slightly related to available forage, which was in turn affected by site preparation. Information on home range use, habitat requirements, and the difference in carrying capacity for mountain beaver under varying site preparations, can assist managers in manipulating habitats in order to minimize colonization and reduce seedling damage. We suggest several integrated pest management strategies to minimize seedling damage by mountain beaver.
Nutria have been present in the Pacific Northwest for more than 70 years, and though their dramatic impacts on wetlands in the southeastern U.S. is well documented, the northwestern populations have been little studied. Using paired exclosure plots, nutria herbivory pressure on the native vegetation is shown to be considerable but dependent on species type and disturbance history. In coastal wetland habitats, nutria selectively feed on forbs compared to grasses, lowering their aboveground biomass. This study also shows opposing responses to nutria herbivory for disturbed and undisturbed plots, with nutria lowering total biomass in areas that have not experienced a biomass-clearing disturbance event and thus have diminished competition intensity.
Nutria were introduced from South America to the United States in the 1930s for fur farms and, due to releases and escapees, are currently established in 15 states. Nutria are important to the Louisiana fur industry, but they also cause extensive damage to coastal marsh ecosystems when populations are high. Louisiana uses an incentive program for hunters and trappers during trapping season (winter), which helps to control the fast-growing nutria populations. While this approach is effective, additional management tools are needed to control nutria year-round and over large areas. Other tools for nutria control include toxicants, baits and lures, and multiple-capture traps. In this study, we evaluated nutria responses to olfactory cues in a Y-maze that potentially could be used as lures in traps or bait stations. Three olfactory cues were selected more frequently than others: Nutria #1 (apple-based commercial lure), nutria gland secretion, and female nutria fur extract. We also evaluated attention by nutria to two species of fertilized and non-fertilized marsh plants that potentially could be used as lures in multiple-capture traps on coastal marsh. Nutria did not show a strong preference for either plant species, but they gave significantly more attention to fertilized plants than non-fertilized plants or soil treatments. Results with nutria urine were equivocal. The materials identified in this study show potential for the development of additional tools to manage nutria populations and their impacts on coastal marsh ecosystems.
Black-tailed prairie dogs are considered an important “keystone” species of the prairies, on one hand, and a nuisance rodent causing considerable damage on the other. To effectively manage prairie dog colonies, a better understanding is needed of the effects of management practices on prairie dogs, their burrow systems, and other species that may use those burrow systems. For example, when fumigants are used to control prairie dog populations, to what extent may other species be affected? We used a burrow-probe camera system to observe animal use of 777 burrow openings. These included colonies both in urban/suburban and natural prairie settings as well as active versus inactive colonies. Burrows were usually probed to a depth of about 2 m, requiring only a few minutes each. Relatively few animals were seen and most were invertebrates. More animals were observed in urban/suburban burrow systems versus prairie burrow systems. Somewhat more animals were observed in active versus abandoned burrow systems. The vertebrates observed were prairie dogs, rabbits, ground squirrels, snakes, a mouse, and a salamander. The implications and possible short-comings of this study are discussed.
The Utah prairie dog (UPD) was listed as “endangered” in 1973; it was down-listed to “threatened” in 1984. Regulatory agencies have realized that protecting and promoting UPD on federal lands alone is not efficient. The U.S. Fish and Wildlife Service (USFWS) and private landowners desire a shift in the current recovery strategy in order to remove the threatened status of UPD as well as provide for management of UPD damage to private property. The time is right to begin a creative management strategy. One suggested new strategy would combine population counts of UPD living on private and public lands toward the recovery goal, as part of the new recovery plan. A survey of agricultural producers in the region with UPD revealed that 70% of the producers feared working with the USFWS on sensitive species issues, because of possible restrictions to their production. To date, the majority of producers would not be interested in creating conservation easements or safe harbors on their property. However, they are willing to work with local Extension agents and the Utah Farm Bureau to create solutions. Therefore, the first step to trying a new approach to UPD recovery will be to foster trust between local producers and regulatory agencies. New programs will focus on building trust, just compensation for losses, stewardship of the land and community, and cooperation.
Surface drip irrigation of field crops has been gaining interest in the farming community. However, rodent damage is one of the major drawbacks for SD acceptance. This research documents the cost of repairing drip tubing and effectiveness of several rodent control methods. Four sites were used to identify cost of repairing tubing. Treatments included untreated drip tubing, tubing that was lightly buried, sprayed with an insecticide or animal repellent, and edible rodenticide placed next to the tubing. Once a leak was found, it took an average of 4 minutes to repair the hole. Each repair had an average cost of $0.67 for labor and repair materials. This does not include time or transportation cost to find the leak. Rodent damage was the same in the untreated versus any chemical management technique. At Site 4, the animal repellent, Ropel® did have less rodent damage (2,392 holes/ha) compared with the untreated (6,049 holes/ha); however, the damage was extensive enough that it was more economical to replace than to repair the tubing. The drip tubing that was slightly buried had the best rodent control (5 holes/ ha) compared with all other treatments (1,771 holes/ha). One disadvantage of burying the drip tubing is removal. Strip tillage along with burying the drip tubing showed excellent resistance to rodent damage and appears to be a cost effective management tool for surface drip irrigation
The Office of Spill Prevention and Response (OSPR) oversees clean-up, natural resource damage assessment activities, and wildlife protection activities at oil spills in California. OSPR contracted with the University of California, Davis (UCD) in July 2000 to establish the Hazing Group (HG) with the goal of preventing birds from becoming exposed in the event of a spill. OSPR activated HG for 2 oil spills in 2004 and 2005. In the Suisun Slough Pipeline Spill near Fairfield on 27 April 2004, a pipeline break released 3 ´ 105.5 L of diesel fuel into a 98-ha freshwater marsh. HG was activated and arrived on scene on 29 April. HG deployed propane cannons and bamboo stakes with mylar along oiled channels, patrolled on foot or by canoe, and fired pyrotechnics at 16 species of birds. Most birds responded favorably and left the marsh or continued on without landing. CAPA rockets and shell crackers were most effective. Hazing continued for 21 days. Post-spill evaluation indicated pre-spill efforts to improve preparedness and response time were effective, but the absence of an assigned vehicle and the location of the primary HG responder away from UCD at the time of call-out increased response time. In the Pyramid Lake Spill near Santa Clarita on 23 March 2005, a pipeline break released 4.8 ´ 106 L of crude oil, which flowed down a creek into Pyramid Lake. HG was activated on 29 March and arrived on-scene on 30 March. HG activities were limited to reconnaissance; few birds were observed on the lake. High winds and rough waters prevented boat operations and were also problematic for shore-based hazing. With the spill contained to a limited area, low bird numbers present, and unfavorable weather forecast to continue, initiation of hazing would have been difficult and of limited benefit. HG was dismissed from the spill response on 31 March. Post-spill evaluation indicated response time was excellent, aided in part by an assigned vehicle. Weather limited hazing, and the location of Pyramid Lake and the timing of the spill was fortuitous with regard to low bird numbers present. On 13 January 2005, oiled birds appeared along the southern California coast between Santa Barbara and Venice. Over 1,400 oiled birds were recovered within 8 days, and up to 5,000 birds may have been oiled along 129 km of coastline. The source of this spill, called the Ventura County Oiled Bird Incident, was unknown. Wildlife officials did not find a major slick on the water. HG was not activated for this spill because there was no identifiable slick or contaminated area to haze birds away from, the impacted area was large, and the impacted species, mostly grebes, are not easily hazed. Guidelines for activation of HG are suggested that take into account the species at risk, the responsiveness of the species to hazing, presence of identifiable source, slick, or contaminated area, imminent likelihood of clean areas becoming oiled, presence of clean areas for hazed birds, the size or extent of the spill, and weather conditions.
Bird-aircraft collisions (bird-strikes) cause serious safety hazards to aircraft, costing civilian aviation at least $496 million annually in the U.S. Non-lethal bird-frightening devices, such as propane exploders, are commonly used to deter birds from airport environments. We conducted a study during August - October 2004 to determine the efficacy of propane exploders utilized with and without concurrent lethal reinforcement activities for altering bird behavior at John F. Kennedy International Airport in Queens, New York. Two groups of 8 propane exploders each were deployed on the airfield. One group of propane exploders was set to “off” (control), whereas the other group was programmed to activate at 15-minute intervals (treatment). This pattern was reversed each week for a 12-week period. In addition, lethal control activities to reduce gull-aircraft collisions were conducted during August and September 2004. We conducted bird observations associated with propane exploders during the lethal control program (8-week period) and following the end of the program (4-week period). The number of bird flocks (≥1 birds) that were within 150 m of treatment (n = 432) and control (n = 442) propane exploders was similar. Simultaneous lethal control activities at the airport did not alter the effectiveness of the propane exploders. Birds responded (e.g., altered flight path) on 3 of 21 (14.3%) occasions when a bird flock was within 150 m of a treatment propane exploder that activated. Our findings suggest propane exploders used in this manner in this airport environment do not significantly alter birds behavior or reduce the threat of bird-strikes. Future research is needed to evaluate techniques such as motion-activated propane exploders to enhance the effectiveness of this tool to reduce wildlife hazards at airports.
An Integrated Management Approach for Nesting Osprey to Protect Human Safety and Aircraft at Langley AFB, Virginia
North American osprey are increasingly becoming a serious aviation safety concern to both military and civilian aircraft. Since 1985, the United States Air Force documented 25 osprey strikes with aircraft, resulting in excess of $1 million dollars in damage. In 50% of the osprey strikes reported to the National Wildlife Strike Database, the aircraft was damaged. Osprey are present from March through September at Langley Air Force Base, where more than 2 dozen nesting pairs have been identified on or immediately adjacent to the airfield. The habituated nesting and breeding behavior of osprey at Langley predisposes this species to impacting aircraft arriving or departing the airfield. The apparent strike risk and flight safety concerns associated with nesting osprey resulted in the development of an integrated hazard/damage management program. As part of the 1st Fighter Wing Bird Aircraft Strike Hazard Plan, the program incorporated a diverse management approach that included nest surveys, behavior monitoring, exclusionary practices, nest removals, egg oiling, traditional hazing, lethal reinforcement, and nestling translocation. Preliminary analysis of the project (2000-2004) suggests the number of nest sites remain constant (range 26-36) from year to year; however, airfield use by osprey has declined 62% since the inception of the program. Exclusion practices, egg oiling, and juvenile translocation are presumed to be the most effective strategies in discouraging nesting and reducing airfield occurrences. Traditional hazing and nest removals had no effect on discouraging osprey behavior or nest site preference. This program will continue to integrate and evaluate management techniques for resolving aviation and human conflicts associated with nesting osprey and may ultimately serve as a technical guide for professional wildlife damage agencies, aviation safety personnel, and natural resource managers.
A New Wrinkle on an Old Method: Successful Use of Scarecrows as a Non-Lethal Method to Prevent Bird Damage to Field Crops in Israel
The use of scarecrows to prevent bird damage to crops probably dates back thousands of years to the beginning of agriculture. Because many of the birds that can cause damage to field crops are protected species, farmers need effective non-lethal protection methods. Despite their perception as “low-tech” and thus ineffective, scarecrows are being used in Israel in a new way, as a cost-effective part of modern bird-damage prevention programs for field crops. Farmers in the Hula Valley in northern Israel placed seated life-size human effigies dressed in yellow hooded rain-suits, each holding a large black pipe (to simulate a shotgun) in fields of winter field crops, as part of a program to prevent damage by Eurasian cranes. Each effigy was also equipped with a life-like facial mask. Experience has shown that approximately one seated scarecrow is needed per 5 ha (about 12 acres) of field crop. To make these scarecrows more effective, and to prevent habituation, the farmers occasionally dressed in yellow rain-suits like the scarecrows, and seated themselves in the field, opening fire with pyrotechnics when birds approached. In addition, the farmers donned the yellow rain-suits whenever conducting any bird harassment activity, such as shooting pyrotechnics from vehicles while patrolling their fields. The birds apparently learned to associate the yellow-suited figures with danger and to keep away from them (and the crops). Farmers who used the new scarecrows in this way found them to be cost-effective because crop damage was almost nil, while damage prevention expenses were also kept low, since the scarecrows are cheap to build and maintain, and less pyrotechnic ammunition was needed for crop protection.
Lettuce is an important economic crop in California, with approximately 101,000 ha in production and a value of $1.3 billion in 2002. Bird damage to lettuce in the San Joaquin Valley, the central coast, and southern California is believed to amount to millions of dollars annually. We evaluated the effectiveness of Flight Control™ (50% anthraquinone applied at 10 L/ha) as a foliar spray for protecting emerging lettuce seedlings from depredation by horned larks. In field enclosure trials conducted near Huron, in the San Joaquin Valley of California, damage to treated lettuce seedlings was 8.5%, compared to 68% damage to untreated seedlings. In a field test, anthraquinone residues on the day of treatment averaged 570 ppm and at Day 50 after treatment were lower than the method of detection (0.063 ppm). However, horned lark numbers using test sites were too low to detect any differences in damage among treated and untreated sites. Anthraquinone offers promise for reducing bird depredations to sprouting lettuce, but additional testing should be conducted to evaluate this repellent in a large-scale field setting.
Aircraft collisions with wildlife pose a threat to human health and safety for both the civil aviation industry and the military. Worldwide, wildlife strikes have resulted in the deaths of more than 157 people and the destruction of at least 140 aircraft since 1990. From 1990-2003, European starlings caused about $2.5 million in damage to civil aviation in the United States and are ranked among the top 21 most hazardous species to aviation. Lethal control to solve wildlife conflicts is often undesirable or impractical. Frightening techniques to keep birds away from airports are available, but may be untested, only temporarily effective, or cost-prohibitive. A new product, “Crow Buster”, was developed in Japan to repel crows from small agricultural plots. The product is based on ChromaFlair® pigments that allow the device to change color depending on the angle at which it is viewed and the angle of light on the product. The Crow Buster is made from lightweight plastic that forms a spiral when hung vertically from the top of the product. The objective of this study was to determine if the ChromaFlair®-based Crow Buster will deter European starlings from occupying starling nest boxes. There was no difference in the presence of nest material between treated and control nest boxes. In nests with eggs, clutch size was similar between treated (4.7 ± 0.2) and control (4.6 ± 0.1) boxes, but the mean initial date of egg laying was delayed 6 days in treated boxes. Because the device provided an initial level of repellency, it could be applied in and around starling nest sites as a deterrent until more permanent control efforts (e.g. modifying habitat) can be employed.
Effective management of vertebrate pest populations is enhanced by greater understanding of stakeholder-pest interactions as well as stakeholder attitudes toward control of the problem species. It has long been reported that black vultures are responsible for depredation of livestock, especially newborns. To gain a better understanding of this phenomenon, we conducted a survey of 374 Florida cattle ranchers, representing roughly 2% of the total number of Florida cattle ranches. A 3-page questionnaire was used to gather information of ranch characteristics and whether or not the ranchers had experienced vulture attacks. In cases where vulture attacks were reported, respondents were asked to quantify the value of property lost to vultures and preventative measures taken to reduce vulture predation. All respondents were asked a similar set of questions regarding coyotes as well as a series of questions concerning their attitudes toward vulture control and regulations. The survey revealed that 38% of respondents had experienced vulture predation that, on average, resulted in over $2,000 damage. Important predictors of vulture predation were ranch size and number of cattle. Attacks were recorded throughout the year, with the greatest number occurring during the winter months. By gaining better knowledge of stakeholder views and opinions, as well as the extent and characteristics of their depredation problems, we can more efficiently address the needs of livestock ranchers to reduce vulture damage.
Depredations to livestock by black vultures are a concern for many producers, and there is an increasing need for effective means to alleviate conflicts between livestock and vultures. One approach to this problem is to identify the roost site that is the source of the offending birds and then disperse that roost. We evaluated this approach in southwestern Virginia, where sheep and cattle operations in the New River Valley have historically experienced depredations by black vultures. During February 2004, we trapped and tagged 200 vultures and equipped 20 of them with radio transmitters. We established data-logger receiving stations at the main roost site in Radford, VA and at 4 nearby livestock operations. We monitored vulture use of the roost and the livestock sites for 2 weeks and then we dispersed the Radford roost using vulture effigies and hand-held lasers. We continued to monitor vulture activity at the livestock study sites for 8 weeks. Our findings showed that although the roost in Radford was dispersed, vulture use of the livestock operations after roost dispersal did not differ from pre-dispersal activity. Vultures in the area apparently shifted to alternate roost sites with no noticeable disruption to their foraging activities. For roost management to be effective against livestock depredations, dispersal activity must include the ancillary roosts as well as the main roost. Furthermore, prompt removal and proper disposal of livestock carcasses should greatly reduce the attractiveness of cattle and sheep operations for foraging black vultures.
Roosting birds of certain species can be agricultural pests, hazards to aircraft on takeoff and landing, and a purported health hazard. Locating roosts of pest bird species and estimating the numbers of birds using them is time-consuming field work, especially when use of different roosts changes seasonally. Since the middle of the previous century, radar has been used to observe early morning bird echoes, then called “ring angels”. Today, large Doppler radars designed for meteorological work can routinely observe bird roosts, even when birds fly at treetop height. Radar images can often locate all roosts within a certain distance from the radar and can provide an indication of the number of birds using each roost and the general location of their food sources. Single images from the lowest tilt angle (lowest elevation) of different radars show roosts in several areas of the country, and successive scans of a research radar across an area becomes an animated picture of the detailed spatial behavior of birds leaving the roost. Applying a computer image recognition technique, the Hough Transform, to single radar-derived images of bird roosts results in objective numerical estimates of roost location and other data. Data are shown comparing ground-truth visual counts of European starling and brown-headed cowbird departures with such quantitative radar-derived data. The radar correctly estimated the central tendency of flight speed of the birds (20 m/sec), time of morning flight (mean 13.2 min past civil sunrise), and roost location (modal error about 2 km). Sometimes (5.1% of identifications) the algorithm found a “roost” that could not be located by field observers; occasionally there were other sources of confusing echo such as vehicles or migrating birds.
I measured the preliminary effects of chicken egg baits treated with DRC-1339 on removing common ravens for the purpose of reducing raven depredation of prairie grouse nests in northeastern Nevada. Greater sage grouse and Columbian sharp-tailed grouse are game species that are declining in distribution and abundance throughout their historic range. Reduced nest success due to egg depredation by ravens is thought to be an important cause of nest failure. Ravens are subsidized nest predators that have substantially increased in abundance throughout their range within the past 25 years. During 2002-2004, I removed ravens from a treatment site using chicken egg baits treated with DRC-1339 to protect sage grouse and a nascent population of reintroduced Columbian sharp-tailed grouse in northeastern Nevada. I performed raven surveys at the treatment site and 2 control sites, located 22 and 53 km northwest of the treatment site, to measure the effects of using DRC-1339. Preliminary analyses indicate chicken egg baits treated with DRC-1339 significantly reduced raven densities at the treatment site, and change in densities over time was different at the treatment site than the control sites (F = 10.212,59, P < 0.001). Also, anthropogenic resource subsidies (i.e., power-lines, roads, agricultural fields, and public landfills) appeared to influence raven abundance. If lethal removal of ravens is implemented as a short-term management action to protect areas from ecological or economical damage, the technique described here is valuable to managers.
When using DRC-1339 Concentrate, applicators have sometimes found that blackbirds will not feed on standard grain baits. While the search for more attractive baits has generally focused on alternate grains, fruits, and occasionally processed foods, a first-rate candidate may be insects. To our knowledge, no feeding tests using red-winged blackbirds have been conducted to measure consumption rates among various commercially available insects. Our results indicated that large-sized mealworms were the best bait for red-winged blackbirds during fall, whereas crickets were favored over small-sized meal¬worms and waxworms in summer. We speculate that choice was based to some extent on the quantity of fat available among the different foods. We plan to conduct similar feeding trials with European starlings.
The economic impact of introduced predators, principally wild dogs, foxes, and feral pigs, on agriculture in Australia varies across space and time but is estimated to be in excess of US$120 million annually. Australian farmers and the government spend a further US$30 million annually attempting to manage the predation and disease impacts of introduced predators on stock and wildlife. The principal chemical tool used to control each of these species is sodium fluoroacetate (‘1080’). Issues relating to target-specificity and perceived inhumaneness of the toxin have led to heavily restricted use of the compound in the U.S. and a recent registration review in Australia. Three current proactive research projects are addressing this issue. The first is investigating a chemical, p-aminopropiophenone or PAPP, that appears to be selectively toxic for introduced carnivores, as well as rapid acting and relatively humane in its mode of action. The compound acts by interfering with oxygen transport in the blood of foxes and wild dogs, resulting in an effect similar to carbon monoxide poisoning. The second project involves testing and commercializing powerful fox, wild dog, and feral pig attractants that may help increase the efficacy and target-specificity of control programs. The first product from this project is FeralMone®, an aerosolized formulation of synthetic fermented egg that is highly attractive to canids. The third project has involved developing a manufactured target-specific feral pig bait package, PIGOUT®. Initial research has focused on the delivery vehicle that contains sodium fluoracetate centralized in an internal core, whilst current research is developing a recently identified humane alternative feral pig control agent. This paper will report on the economic impact of introduced predators in Australia, the recent Australian sodium fluoroacetate review recommendations, as well as summaries of current research into new predator control tools.
The Electronic Calling System: Effectiveness for Capturing a Wide Variety of Offending Wildlife Species in Nevada, 2002 thru 2005
In 2002, a Wildlife Services wildlife biologist from Nevada, a Wildlife Services wildlife specialist from Oregon, and a mechanical engineer from California came together with their ideas about designing an effective and easy-to-implement electronic calling system (ECS). Their common vision was a for a self-contained, user-friendly device that would be highly effective at attracting or “calling in” specific offending individuals of various species to a given location, during a specific time period, and hold them at or near that site for a period of time. Through field trials and modifications, an ECS named the “Chuck Box” was developed. It proved to be an effective self-contained tool, when the correct sound and time combinations were employed, and we describe our success in using it for mountain lions and coyotes. It was especially useful in “anchoring” wide-ranging and/or sporadically problematic animals to a site where control tools could easily be utilized or wildlife damage management actions could be initiated. In 2004, non-wildlife sounds were added to the memory card of the unit, making the Chuck Box also function as an effective non-lethal scare device. Thus, the Chuck Box can provide non-lethal harassment or provide support during lethal wildlife damage management activities. Field results indicate that the Chuck Box can be highly effective in increasing capture success, holding animals in the proximity of the station, and in deterring various wildlife species
Wildlife Damage Management Protection Efforts for a Vulnerable Pronghorn Antelope Population in Northwestern Nevada: 2000 through 2004
In January 2000, the Nevada Board of Wildlife Commissioners (Wildlife Commissioners) directed Nevada’s state game management agency, the Nevada Department of Wildlife (NDOW), to secure wildlife damage management (WDM) assistance from the United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services Program (WS) for the purpose of protecting a struggling population of pronghorn antelope located in northern Washoe County, Nevada. NDOW had documented, over a several-year period, that this northern Nevada antelope population had consistently demonstrated unacceptably low fawn recruitment levels. While NDOW was unsure of the cause for this consistent poor production record, the Wildlife Commissioners suspected “excessive” fawn predation to be one of the primary causes for the unacceptable recruitment levels. WS was contracted by NDOW to initiate fawn protection efforts for this population with an emphasis on coyote predation management. In collaboration with WS, NDOW mapped out a designated protection area where WDM activities would be conducted, established that WDM activities would only be conducted during the vulnerable fawning period, and set a target recruitment level for the herd which, when reached, would conclude the WDM activities. Prior to the initiation of WDM actions, WS personnel conducted several predator surveys to establish the coyote incidence level within the designated protection area. These data were to serve as a baseline indicator to help gauge the effectiveness of ongoing coyote removal efforts. While WS removed any coyote encountered within the specified protection area during the critical fawning season, removal efforts were primarily directed at older, territorial coyotes. The doe-to-fawn ratio was determined by NDOW at the end of each season, and when the ratio reached NDOW’s predetermined level of 32 fawns per 100 does, WDM activities were terminated. Additional benefits stemming from the antelope project included reduced predator pressure on other game species inhabiting the same area (such as mule deer), and collection of coyote blood samples for the monitoring of wildlife diseases such as plague.
Wildlife Damage Management Protection Efforts on a Mule Deer Population in Eastern Nevada: 2003 thru 2005
In September 2003, the Nevada Board of Wildlife Commissioners directed the Nevada Department of Wildlife (NDOW) to contract with the USDA APHIS Wildlife Services Program (WS) to conduct wildlife damage management (WDM) activities for the protection of mule deer in eastern Nevada. Responding to the Commission’s directive, NDOW requested WS to initiate wildlife damage management efforts to protect a population of adult and juvenile mule deer in Lincoln County. The coyote was the only predator targeted for removal from the project area by various removal methods. WS personnel also collected coyote mandibles from the project area, and the cementum aging process was used to determine the age structure of coyotes prior to and during the ongoing WDM protection efforts. Results from the tooth aging analysis indicate that the average age of coyotes dropped somewhat during the second year of removal, although not significantly. Mule deer fawn and adult populations are monitored by NDOW to determine what effect(s) coyote removal is having on the mule deer population located in the protection area. The protection area is mainly comprised of public lands managed by the Bureau of Land Management and the U.S. Forest Service, and nearly all WDM activities were conducted on these public lands. This is an ongoing 5-year mule deer protection project. As an added dimension of the resource protection efforts, WS collected blood samples from coyotes removed during WDM activities to permit the monitoring of various wildlife diseases by the Centers for Disease Control (CDC) and Washoe County Vector Control.
The Coyote Lure Operative Device (CLOD) is a bait delivery device designed to deliver chemicals such as vaccines, sterilizing agents, predacides, and physiological markers to coyotes. Coyotes have activated the device in the field when it is filled with placebo baits, but measured delivery of an active ingredient has never been attempted. We developed a dose-response relationship for pentachlorobenzene (PeCB) residues in coyote serum and used the CLOD to deliver PeCB to captive coyotes. Twenty-two days post dosing, PeCB residues were detected in serum samples collected from every coyote that activated the CLOD. No residues were found in controls. We conclude that PeCB can be used as a physiological marker for identification of coyotes that activate CLODs. Using PeCB to quantify CLOD consumption met with moderate success and recommendations for future research are provided.
The Impact of Predation on the Threatened Endemic Kereru (Hemiphaga novaeseelandiae) by Mammalian Predators on Banks Peninsula, New Zealand
The kereru (New Zealand pigeon) is a threatened endemic species. Predation of eggs, chicks, and adults at nests by mammalian predators is considered to be a major potential threat. The impact of mammalian predators on kereru populations was studied on three remnant native bush areas on Banks Peninsula, New Zealand, from February 2004 to March 2005. In this study, 15 kereru were fitted with radio-transmitters and intensely monitored for survival. Three radio-tagged kereru were lost at the beginning of this study and their transmitters were redeployed, so a total of 18 radio-tagged kereru were monitored for predator-induced mortality. Five adult kereru died, 3 as a result of predation. A cat was recorded on video preying on one adult. It is hypothesised that cats were responsible for preying on other kereru during this study. Rat and possum predation limited nesting success; however, this could have been offset by replacement nesting after nest failures. Cats preyed on chicks and adult kereru, which impacted the breeding viability of the adult population. Kereru may be able to withstand some nest predation pressure if the pair is able to re-nest in the same season. However, the ability of kereru to re-nest is reliant on them having an adequate food source, so this may not be possible in poor seasons. These assertions require population modelling to determine their relative importance. Nesting success would benefit from rat and possum control during good breeding seasons. Adult survival would benefit from the control of predators such as cats and stoats. However, as kereru have integrated into urban habitat, managers must consult with the community before conducting predator control.
Coyotes have expanded their range throughout much of North America, aided by the extirpation of wolves, alteration and transformation of habitat, and urban sprawl. Humanized landscapes have worked to the coyote’s advantage by offering an abundance of food, water, and shelter. Unfortunately, intentional and unintentional feeding of coyotes has also resulted in increased encounters and conflicts. How communities address such conflicts generates impassioned debate. Many state wildlife agencies and local municipalities lack the resources to effectively implement proactive strategies before encounters escalate to conflicts. Moreover, lack of agency coordination, combined with a largely uneducated populace, hinders effective conflict resolution. Consequently, responses to coyote conflicts are usually reactive and fail to address the root causes of most conflicts, i.e. a constant food source. Failure to address these root causes often leads to a vicious cycle of trapping and killing. Moreover, inconsistent and exaggerated reports of coyote attacks can lead to heightened public fears, which may limit the opportunity for establishing long-lasting proactive coexistence strategies. This paper provides an overview of coyote ecology in urbanized landscapes and considers several case studies of communities that have developed effective coyote coexistence programs.
In 2001, Marin County, California, replaced its Wildlife Services (WS) predator damage management effort with a county-run program that cost-shares non-lethal methods of predation reduction with ranchers and also compensates them for sheep and lamb losses. This paper attempts to compare the former WS program with the current program, using such variables as livestock lost to predators, coyotes and non-target animals killed, and program costs. Inconsistent data collection and lack of information make a clear comparison of the two programs difficult; however, some sheep producers continue to suffer predation loss rates that threaten the sustainability of their enterprises.
Strategies to assess and reduce risk associated with disease agents in wild animals must be based upon thorough knowledge of the epidemiology of the disease agent, specific local information, and other factors. Risk evaluation and management efforts will involve organizations with differing expertise and cooperation will be essential between wildlife management, public health, and domestic animal health agencies. Risk reduction strategies may be based upon manipulation of the disease agent, the host, the environment, and/or human activities. Management of human activity, particularly the promotion of biosecurity, may be the most efficient strategy because other measures are more difficult and expensive. The science of risk assessment and disease management in wildlife is growing and evolving as new situations arise and as new methods are developed to meet the needs of wildlife resource, animal agriculture, and public health interest groups.
Public health surveillance is defined as the ongoing systematic collection, analysis, interpretation, and dissemination of health data. Public health surveillance is a dynamic process because it represents information for action. Action taken may in turn affect how and what further surveillance is performed. Surveillance data is collected from a variety of different sources including disease reporting, laboratory reporting, sentinel systems, and surveys. The Vector-Borne Disease Section of the California Department of Health Services performs surveillance primarily for diseases that are carried by rodents, ticks, mosquitoes, and fleas. Surveillance for these diseases is often multifaceted, involving the monitoring of human and animal diseases, monitoring vector populations, and monitoring for infections in these vectors. Information gained from surveillance of vector-borne diseases is used to guide control or prevention measures. Examples of the surveillance systems for West Nile virus, plague, and Lyme disease are presented.
Lyme disease (LD), caused by the spirochete Borrelia burgdorferi (Bb), is the most commonly reported vector-borne disease in the United States. We have been studying the ecology, epidemiology, and prevention of LD since 1982. The primary objectives of this research are intended to clarify the transmission cycles of Bb and closely related spirochetes in diverse habitats; to determine what behaviors and environmental factors elevate the risk of human exposure to Bb-infected ticks; and to evaluate preventive methods. Several genospecies of LD spirochetes are maintained in transmission cycles involving western gray squirrels, dusky-footed wood rats, California kangaroo rats or deer mice, and three species of Ixodes ticks. The western gray squirrel has been implicated as a primary reservoir host of Bb in dense woodlands. The western black-legged tick, Ixodes pacificus, especially the nymphal stage, is the primary bridging vector from wildlife reservoirs to people. In Mendocino County, the prevalence of spirochete-infection in the nymphs typically averages between 5 and 10% (range, <1% to 41% among individual sites) in various subtypes of dense woodlands. Some activities that were found to contribute significantly to risk of exposure to LD or host-seeking I. pacificus ticks included cutting wood, and contact with either low vegetation bordering the uphill margins of hillside-hiking trails or leaf-litter areas and wood in dense woodlands. To determine how people might become infested with I. pacificus nymphs, six behaviors were evaluated as potential risk factors for encountering the nymphs in a hardwood forest. Activities entailing considerable contact with wood (e.g., sitting on logs or against tree trunks) resulted in greater infestation by nymphs than behaviors involving exposure solely to leaf litter. The ultimate goal of this long-term research is to use the basic knowledge gleaned to develop and implement strategies for reducing human exposure to LD and other tick-borne agents.
Since the invasion of the mosquito-borne, West Nile virus (WNv) into North America in New York City (NYC) in 1999, the distribution of the virus has expanded throughout most of the continent during the ensuing years, causing mortality in hundreds of thousands of native and exotic birds and producing tens of thousands of equine and human cases. The initial outbreaks in the NYC area in 1999 were intense in local bird populations, with small outbreaks in humans and equines. Then, WNv spread north and south from this focal area during the next 2 years. The northward and southward sequence of dissemination continued as WNv began to encompass the remainder of the continent. Migrating birds are thought to be the one of the major contributors to the rapid dissemination of this mosquito-borne virus. The temporal and spatial pattern and rapidity of the continental spread of WNv, as detected by the national surveillance system, match the semi-annual migratory movements of hundreds of millions of North American birds. The subsequent dissemination of the virus to Canada, the Caribbean, Mexico, Central America, and now South America fits this method of spread as well. The strain of WNv introduced into the U.S. had increased virulence for North American birds, which quickly became apparent after its introduction and from the subsequent avian epizootics it caused. More than 200 species of birds experienced mortality, especially corvid species such as the American crow, blue jay, and several species of magpies, and recently the greater sage grouse. These species were particularly susceptible to this virulent strain of virus, as demonstrated in experimental studies and from dramatic die-offs during the summer virus transmission seasons. Bird mortality from WNv peaks during August-September at the height of the mosquito-transmission period but extends from April to November each year in some states. This mortality in crows and other corvid species was used as a sensitive sentinel system to detect the presence and movement of the virus through a public health reporting and laboratory testing national surveillance program. Mammal species were frequently infected, and some suffered mortality. The nationwide bird mortality from WNv infections was dramatic in North America during the last 7 years, but the actual impact of the mortality on bird populations is not known because of the insensitivity of national population data available on birds. Few regional declines in bird populations have been detected; however, the impact of WNv on local populations of crows and sage grouse has been observed in some localities. The geographical distribution of WNv activity is not continuous across local landscapes, and unexposed birds can then serve as a source to repopulate local impacted areas when overall populations are high. West Nile virus persists through the winter periods and reappears annually in the spring in temperate regions of the continent. The mechanisms responsible for this recrudescence are unique and largely unknown. Focusing on these overwintering locations with targeted mosquito control could suppress early season initiation of virus transmission and possibly prevent subsequent summer amplification. Integrated pest management aimed at controlling mosquito populations is currently the only effective approach to control this disease.
Granulocytic anaplasmosis (GA) is a disease of humans, domestic animals, and wildlife caused by Anaplasma phagocytophilum, formerly Ehrlichia phagocytophila, E. equi, and the unnamed agents of “human granulocytic ehrlichiosis” (HGE). This pathogen is inoculated into host skin by the bite of Ixodes spp. ticks, including I. pacificus in California and I. scapularis in the eastern U.S. After inoculation, A. phagocytophilum disseminates to the blood and is phagocytosed into host neutrophils. The clinical characteristics of GA in people vary from no symptoms to fever, headache, neurological symptoms, and occasionally death. Horses with GA may experience high fever, depression, reduced ability to eat, limb edema, jaundice, and ataxia. GA is an emerging disease in the eastern U.S. but only a handful of human cases have been reported in the western U.S., despite relatively common reports of disease in horses and dogs. Wildlife and dog-sentinel studies have clarified that infection is common in the coast range mountains and Sierra Nevada foothills, with ongoing research focusing on ecological determinants that can modify the prevalence of infection in any particular area. One known reservoir is the dusky-footed woodrat. However, important, poorly understood ecological determinants serve to modify the probability of rodent as well as human infections, including climate, vegetation, and possibly the presence of other reservoir-competent rodents and nidicolous woodrat-specialist ticks such as I. spinipalpis.
Chronic Wasting Disease (CWD) was first described in captive mule deer in a Colorado research facility in 1967 and subsequently classified as a transmissible spongiform encephalopathy in 1978. The first detection of CWD in a free-ranging population was in Colorado elk in 1981. During the 1990s, CWD was identified in free-ranging mule deer, white-tailed deer, and elk in Colorado and Wyoming. By 2000, CWD was considered a disease affecting free-ranging and captive cervids, with a limited distribution in several western states and western provinces in Canada. Following the outbreak of Bovine Spongiform Encephalopathy in Great Britain during the 1980s and resulting variant Creutzfeldt-Jakob disease in humans in the 1990s, CWD began to garner more attention. Surveillance for CWD increased in both captive and free-ranging cervids, and the disease was subsequently identified in numerous additional locations. Currently, CWD has been detected in either free-ranging or captive deer and elk in 14 states and 2 Canadian provinces. Most recently (2005), the disease was detected in free-ranging deer in New York, West Virginia, Kansas, and Alberta and in captive herds in New York. Across most of the geographic range where CWD has been detected, disease prevalence remains low. However, the disease has continued to spread from the initial foci where it was detected and continued to increase in prevalence. Management efforts to contain or eradicate CWD have not yet been successful, and in some local areas the disease has reached disconcerting levels.
USDA APHIS Wildlife Services’ National Wildlife Disease Surveillance and Emergency Response System (SERS)
USDA APHIS Wildlife Services has established a National Wildlife Disease Surveillance and Emergency Response System (SERS). The goal of SERS is to develop and implement a nationally coordinated disease monitoring system aimed at safeguarding wildlife populations, agriculture, and human health and safety from disease threats. The SERS is designed to provide an infrastructure capable of assisting state, federal, and tribal agencies with both routine disease monitoring and in addressing wildlife disease threats. Supplementing existing programs with a nationally coordinated wildlife surveillance system facilitates information exchange among the programs, ensures diseases of national bio-security concern (e.g., plague, tularemia, avian influenza, classical swine fever) are adequately sampled, and additionally, provides field and laboratory infrastructure which is available to assist other agencies with sampling collection and disease diagnosis during emergency outbreaks. The SERS currently consists of national program staff and 23 wildlife disease biologists distributed throughout the country. During 2005, these biologists provided disease surveillance assistance to 17 states for chronic wasting disease, 19 states for West Nile virus, 18 states for rabies, and numerous other states for surveillance of 18 other diseases. In 2005, the SERS program coordinated national level surveillance systems for plague and tularemia (18 states) and for diseases in feral swine (14 states). Currently, SERS is coordinating a National Early Detection System for Asian influenza H5N1 in migratory birds, in collaboration with other federal and state partners.
Urban Dingoes (Canis lupus dingo and Hybrids) and Human Hydatid Disease (Echinococcus granulosus) in Queensland, Australia
Urban dingoes are known to occur along most of the Australian eastern seaboard but are particularly common in Queensland coastal cities and towns. Urban dingoes cause significant damage to domestic pets and livestock and present four serious threats to human health and safety: attacks on humans, attacks on domestic animals, zoonotic disease transmission to humans, and the psychological and emotional trauma to affected residents. I have begun to monitor urban dingoes in three metropolitan and regional Queensland coastal cities using GPS datalogging collars to determine habitat use by dingoes in urban communities, assess their reliance on bushland areas, and evaluate their potential role in the epidemiology of zoonotic diseases, including human hydatid disease (caused by the parasitic tapeworm Echinococcus granulosus). Similar to urban predators on other continents (e.g., red foxes and coyotes), I found urban dingoes to have smaller home ranges than their rural counterparts, exhibit flexible habitat requirements in a resource-rich urban environment, and potentially have a pivotal role in the transmission of E. granulosus to humans in built-up areas. Some challenges of urban predator and zoonotic disease management are discussed.
This paper describes issues and concepts relevant to economic modeling of oral rabies vaccination (ORV) campaigns for managing wildlife rabies. Economic models of ORV are mathematical expressions used to predict and draw inferences about the costs and savings likely to be recouped by these rabies management efforts. Costs that are prevented due to ORV campaigns convert to savings. Comparison of campaign duration, bait cost, bait density, and bait distribution data for North American ORV campaigns showed that: 1) campaigns are lengthy, 2) those involving raccoons entail greater bait densities (i.e., related bait costs) and per unit area bait-distribution costs than those involving foxes and coyotes, and 3) all entail “enhanced” surveillance and establishment of maintenance barriers (i.e., deter translocation or reintroduction of new cases) upon completion. Key modeling issues were: model parameterization, ORV cost variables (i.e., bait costs, bait densities, and unit area distribution costs), time horizon, contingency costs, and ORV host specificity.
The U.S. Department of Agriculture distributes more than 10 million tetracycline-containing rabies vaccine baits to control the spread of wildlife-vectored rabies to humans, pets, and livestock. To estimate the percent of target species consuming the baits, raccoons were collected in baited areas and teeth were analyzed for the presence of the tetracycline biomarker. Several incidents of low biomarker detection rates prompted an investigation of the stability of the biomarker in the baits. These studies indicated that a portion of the tetracycline was converted to epitetracycline. Additionally, significant quantities of both compounds were trapped in the polymer which is homogeneously distributed throughout the bait. This situation is likely responsible for low biomarker detection rates. To alleviate this problem, we developed an alternative bait matrix which permits increased stability and bioavailability of the tetracycline biomarker. This new bait matrix increased the availability of the tetracycline marker from 25.2 to 87.3% and decreased epitetracycline formation from 12.4 to 3.6%.
Terrestrial Rabies Surveillance on Cape Cod: A Community-Based Multi-Agency Strategy to Provide Critical Information for Rabies Control
Knowledge of the rate and extent of spread of epizootic diseases is critical to facilitate effective management. Terrestrial rabies was first detected in spring 2004 on Cape Cod Massachusetts, compromising a long-standing ORV zone established from the west side of the Cape Cod Canal to serve as a barrier to raccoon rabies spread onto the Cape. In March 2004, USDA Wildlife Services and local and state cooperators implemented a surveillance program to track the spread of rabies on Cape Cod for planning contingency action strategies aimed at containment and elimination. During 13 months of enhanced rabies surveillance, 198 (167 raccoons and 29 skunks) out of 942 specimens tested positive for rabies. We discuss management implications of these results to the Cape Cod Oral Rabies Vaccination program and to other integrated rabies control programs.
A Preliminary Field Trial of Bait Stations for the Delivery of Oral Rabies Vaccine: Can Varying Diameter Exclude Non-Target Species?
Delivery of oral rabies vaccine can be an effective method for combating rabies, but broadcasting vaccine sachets over wide areas creates the potential for non-target species to ingest vaccine baits before the target species encounters them. An alternative is to present the vaccine at a bait station designed to allow access by target species, while excluding some non-target species. We tested whether bait stations constructed of PVC pipe of 3 different diameters (10, 15, and 20 cm) differed in their effectiveness in allowing access by striped skunks versus other, non-target, nocturnal mammals in the urban environment of Flagstaff, Arizona. We placed bait stations in sets of 3 at 13 locations during late February and early March 2005 and monitored their use for 5 nights using digital still cameras. We recorded visits by striped skunks, gray foxes, raccoons, and domestic cats and dogs. Large-diameter tubes were used by all species, though large dogs had limited access, and small-diameter tubes were entered only once (by a skunk). Medium-diameter stations were used by all species except dogs, but skunks entered these stations more readily (81% vs. 44% or less), indicating that baits in 15-cm tubes would be more readily accessed by skunks. If striped skunks are the primary target species, we recommend the use of medium-diameter bait stations, as these stations excluded all dogs and reduced bait uptake by cats, foxes, and raccoons. If foxes and raccoons are also targeted, large-diameter stations will be required, and these will be available to all cats and some small dogs but should exclude larger dogs. Given the cost of this type of bait station in both time and money, we recommend their use only in limited areas where potential interaction with non-target species is of special concern. However, when one considers the value of human life, the cost may be negligible.
A study was initiated in 2005 to examine the ecology of gray fox in Texas, to assist the oral rabies vaccination program. The study’s objectives are to examine space use and long-distance movements of radio-collared foxes, and to provide landscape-level ecological assessment of fox dispersal and the factors that influence it. Concurrently, GIS habitat layers being built will assist in understanding fox movement and gene flow.
This paper presents a general summary of an economic assessment of the United States Department of Agriculture (USDA), Animal and Plant Health Inspection Service (APHIS), Wildlife Services (WS) Program in California (CA). Detailed analyses quantified WS economic benefits to each of the 38 counties that contributed cooperative funds in 2004, with an aggregate report of county results used to form an overall statewide estimate of the Program’s value. Four general categories of wildlife damage management activities were: Agriculture, Health and Human Safety, Natural Resources, and Property. Two general methods of determining economic valuation were employed to quantify benefits: replacement-cost method, and damage-avoided method. Results showed that the protection of livestock, particularly sheep, cattle, and goats, from predation was a main activity of WS–CA personnel in each of the cooperating counties. Annual estimated replacement costs for WS–CA operations for Year 1 and Year 2 of the analysis (i.e., approximately equivalent to fiscal years 2003 and 2004, respectively) totaled $6,605,234 and $8,602,590 for the combined counties, respectively. Mean replacement costs for WS operations in the cooperating counties in Year 1 and Year 2 equaled $173,821.95 and $226,373.13, respectively. Given that the counties paid an average $51,798.10 share to WS–CA in 2003, the counties would have incurred averaged net increased expenses of $122,023.85 and $174,575.03 for similar services offered by commercial wildlife damage management companies.
The feral hog is an Old World species introduced to Texas by early Spanish explorers. Populations in Texas are descended from European wild hogs introduced for sporting purposes, and from escaped domestic swine that have established feral populations. Today, Texas has a feral hog population estimated at about 2 million animals, the most of any state. Feral hogs are considered a pest throughout much of their range. They are responsible for damaging crops, pasture, rangeland, livestock, and wildlife resources. Because of their reproductive capacity and their omnivorous eating habits, the feral hog population has rapidly increased across the state over the past 25 years. This increasing population, and resulting economic losses, have led resource managers to investigate alternative methods of managing feral hog populations. The uniqueness of the Texas Coastal Plains habitat lends itself to aerial hunting more often than a habitat type with a more densely formed overstory. We review the impacts of aerial hunting operations in Matagorda County in the Southeast Texas Coastal Plains.
Feral hog populations have long been established in Texas. Expanding hog populations and increasing urban sprawl have brought humans and feral hogs into contact even in urban areas. The Fort Worth Nature Center & Refuge is a 3,600+ acre urban green space owned by the City of Fort Worth and managed by employees of the City’s Parks and Community Services Department as a natural, native landscape. Evidence of feral hog activity on the site was first documented in 1999. Efforts to develop a suitable control plan that would protect the natural resources of the refuge, while being cognizant of internal and external stakeholders’ diverse concerns, were undertaken over a 2-year period. These efforts culminated in the implementation of a successful ongoing trap and euthanize feral hog control program that has received wide acceptance from all stakeholders.
Research interests in feral hogs typically involve their negative impacts on ecosystems or their potential as a disease reservoir, especially with disease transmission to domestic swine. Authors within scientific literature state that feral hogs were captured as part of their research, but usually fail to mention specific conditions in which hogs were captured. Novice researchers of feral hogs must rely on ‘word-of-mouth’ to acquire this information or learn it by trial and error. Our objective was to place this knowledge into the scientific literature as an aid to future researchers of feral hogs. Feral hogs were captured in box traps or corral-style traps baited with sour corn in eastern and southern Texas during April 2004 - June 2005. Daily weather conditions (i.e., high and low temperatures, humidity, average wind speed, and precipitation) were obtained from the nearest weather station for each trapping location. A predictive model using logistic regression was developed from data collected in eastern Texas to predict the success of feral hog trapping on a given night based on significant weather variables and then tested on data collected from southern Texas. A successful night of trapping was defined as ≥1 hog being captured. A total of 212 feral hogs were captured during 166 nights of trapping (1,558 trap-nights). The threshold of 22°C for the daily minimum temperature was the only significant (Chi-square = 26.5, df = 1, P < 0.0001) weather variable found. The majority of hogs (97%) were captured when the daily minimum temperature was below 22°C. The model could correctly predict (95%) when trapping success of feral hogs was unlikely (daily minimum temperature ≥22°C), but it was less accurate (50%) in predicting the success of feral hog trapping when the daily minimum temperatures were <22°C. Because the majority of feral hogs live in areas with hot, humid climates during the summer (i.e., southeastern United States), trapping success, especially during July and August, would be unlikely. Research schedules and budgets should be planned to avoid such periods of extreme heat.
The brush-tailed possum is an introduced mammalian pest from Australia. This ubiquitous, nocturnal animal occupies every suitable habitat throughout New Zealand and causes over $40 million (NZD) per annum of direct damage to the country’s economy. To this must be added the intrinsic values associated with possum damage to the conservation estate and native flora and fauna. Rural landowners arguably suffer the greatest effects of possums through grass loss resulting in competition with stock, and the possibility of bovine tuberculosis being spread by possums to farmed cattle and deer. In the upper North Island, the Waikato Regional Council (also known as Environment Waikato) has developed a fresh approach to working with rural landowners to achieve effective and sustainable possum control over large (20,000 ha plus) areas of private and government owned lands. There are currently 12 schemes managed, covering in total 155,000 ha and involving over 770 landowners. The procedure for implementing schemes is necessarily comprehensive but flexible enough to have seen seven modifications to the process since 1998. The process is constantly evolving to ensure that control remains effective and meets the expectations of scheme members and the Council. Environment Waikato, having secured a community mandate of at least 75% of support in each proposed area, undertakes and funds initial control to a predetermined residual trap catch density. Leaving landowners to maintain low possum numbers themselves through trapping, shooting, and poisoning techniques has not proved sustainable in the long-term. Now, maintenance work is carried out by professional contractors and funded by landowners through a targeted property rate (dollars per ha owned). Such an approach has produced significant results, better utilizes contractor time and expertise, and frees farmers up to concentrate on their core task of farming.
The brushtail possum is a significant conservation pest and major vector of bovine tuberculosis in New Zealand. Previous control simulation studies have suggested that aerial control with bait containing sodium monofluoroacetate (1080) is the most cost-effective large-scale possum control strategy. However, there is a growing awareness that the survivors of 1080 control can develop ‘bait shyness’, and this can markedly alter the efficacy of ongoing 1080 control operations. Several alternative toxicants are registered for possum control but all are ground based, differ in their mode of action, and are more expensive than aerial 1080 control. A new possum control simulation model was developed to assist in identifying the most cost-effective control strategy that would achieve a sustained 80% population reduction, given bait-shy behaviour and immigration from adjacent non-controlled areas. The simulation results indicated that it is possible to achieve a sustained 80% population reduction (over a 10-year period) using a 1080-based control strategy, provided at least 90% of all ‘susceptible’ possums are killed in each control operation. In the event of an unsuccessful 1080 control operation (i.e., only a 60% kill), cyanide bait plus trapping, or brodifacoum bait provided the most cost-effective strategy of ‘mopping up’ 1080 bait-shy survivors. However, sufficient numbers of traps must accompany the cyanide bait to ensure that the majority of 1080 bait-shy possums are targeted. Sensitivity analysis indicated that the most important variable influencing the overall success of any control strategies was the rate of re-colonization following control. With the high rates of immigration that are sometimes observed in small forest reserves (i.e., <100 ha), it was not possible to sustain an 80% population reduction using any combination of toxicants. However, higher rates of immigration are probably exceptional and the rate used in these simulations is considered more typical, particularly for moderate-to-large forest stands where most possum control is conducted.
Use of Fatty Acid Profiles to Distinguish between Selected Game Fish and Farm-Raised Channel Catfish
Establishing the impact of double-crested cormorants on commercial farmed channel catfish production using visual assessments of cormorant GI tract contents is complicated by, first, the difficulty in distinguishing between partially digested fish of different species, and secondly, the possibility that the fish appearing in the diet have a natural source of origin. We analyzed the fatty acid profiles of selected game fish and farm-raised channel catfish to establish profiles that may allow for the application of this technique in establishing cormorant foraging patterns. We obtained for analysis farm-raised channel catfish from three commercial producers and one research facility. For comparison, we also collected channel catfish, gizzard shad, green sunfish, bluegill, and largemouth bass from natural waterways. A total of 12 sample groups were analyzed. Lipids were extracted using a modified Folch extraction and trans-esterified in 3N HCl in methanol. The resultant fatty acids were identified using gas chromatography/mass spectrometry. The relative mass percent distributions for the major fatty acids were calculated for each individual. A classification tree analysis was performed to identify groupings based on these individual fish distributions. These preliminary results have led us to conclude that it is possible to distinguish not only between farm-raised channel catfish and game fish in the diet of cormorants, but that it may be possible to identify the source of the farm-raised channel catfish in the diet. The management implications are that it may be possible, based on fatty acid analysis of GI tract contents of cormorants, to assess the actual impact of birds from a given roost or colony on a specific channel catfish producer.
Managing the Small Indian Mongoose (Herpestes javanicus) in the Midst of Human Recreation: What is the Optimal Approach?
In natural recreation areas, habituated wildlife can pose a threat to visitor health and safety by transmitting disease or causing physical injury. Although removal of problem wildlife can help to alleviate these problems, it can also be a labor-intensive, costly practice. To improve the efficiency of a removal program, trapping efforts should be directed towards the spatial and temporal peaks of the target species’ activity patterns. An animal’s activity is often dictated by environmental conditions such as season or lunar phase; however, in a recreation area, it can also be affected by anthropogenic factors such as human presence and provisioning of food sources (i.e. trash cans or picnic areas). A species can 1) be attracted to anthropogenic food sources when human presence is highest, or 2) be attracted to anthropogenic food sources, but only when humans are not present, or 3) avoid anthropogenic food sources and human presence entirely. Each of these scenarios would necessitate a different management strategy to achieve the highest level of trapping efficiency. In the Caribbean National Forest, Puerto Rico, small Indian mongooses are currently controlled by removal trapping to reduce the threat of rabies transmission. Although trapping usually occurs diurnally near areas of high human use, it is unknown whether or not this strategy targets the highest number of animals. Using radiotelemetry, we investigated the movement behavior of 7 mongooses trapped in the picnic areas. We determined animals’ hourly travel distances, activity levels (moving or stationary), and distance of animal locations from human structures (trails, trash cans, and picnic cabanas); and compared these measures between days of high and low visitorship. The distance mongooses were found from human structures was not affected by the day of the week. Activity levels and movements varied by day, but it was unclear how this variation was affected by forest visitor levels. This paper will discuss how these results can be used to develop the most efficient trapping strategy.
The Invasive Animals Cooperative Research Centre: An Australian Initiative of Relevance to North American Vertebrate Pest Management
Following a successful bid to the Australian Government’s Cooperative Research Centres Program, the new Invasive Animal CRC commenced its operations in 2006. The IA CRC will focus on helping to solve invasive animal (vertebrate) pest problems through the development of commercial outputs, integrated strategies, and a business partnership that brings together national and international skills in science, management, commerce, and industry. Comprising a large number of members (41), the IA CRC will assemble critical mass to address a national problem, and it will bring together private and public land managers to integrate approaches to invasive animal management. This unique partnership will deliver the means to deal with existing high-profile invasive animal pests as well as those that have the potential to cause catastrophic impacts in the future. Outcomes will help solve the prominent and costly impacts of invasive species on agricultural, environmental, and social values.
A Live Trap Loaning Program has evolved to address urban wildlife problems in Reno, Nevada. The program, operated by USDA Wildlife Services, has responded to the public’s need to address urban wildlife problems in the absence of an active Wildlife Services specialist in this urban area. The species for which most of the live traps (cage or enclosed) have been requested, since the program’s initiation in FY 1992, are California ground squirrels, raccoons, and striped skunks. We discuss information transfer and educational components of this program, which convey to the public information on the biology of target species, proper handling of non-target catches, handouts, and options available for resolving their wildlife problems.
Vertebrate pesticides for wild animal control in New Zealand came under scrutiny in the 1980s and 1990s, which engendered considerable research to update the toxicology databases of older compounds, such as 1080 or diphacinone, to meet current international registration standards. In parallel there was a focus on identifying “use patterns” and formulations that are effective at killing pests and less hazardous to other wildlife. Improved bait quality and reduced sowing rates for 1080 bait for possum control in New Zealand, down from 10-15 kg of bait per hectare to 1-3 kg, has been accompanied by increased effectiveness and reduced non-target risk. This has been coupled with an improved understanding of 1080 toxicology and risk communication amongst pest control professionals and with the community. In addition, in vivo metabolism and persistence studies coupled with field surveys have improved understanding of the toxicokinetics and non-target effects of different anticoagulants. This enabled improved choice of tools for island versus mainland use in New Zealand. The risks associated with “one-off” applications of baits containing second-generation anticoagulants for rodent eradication on islands are considered to be very substantially outweighed by the potential benefits to their ecosystems. On the mainland, contamination of wildlife and game species and risk of secondary poisoning have been substantially reduced by switching from second- to first-generation anticoagulants. Finally, these developments were coupled with the identification of improved baits for ground control of possums and rodents, such as encapsulated cyanide and gel baits containing cholecalciferol, which in turn reduced an over-reliance on 1080 and anticoagulants alone. Nevertheless, safer use patterns, improved formulations and target specificity, and new vertebrate pesticides are still required, and this will be a major challenge for the 21st Century.
Ecological and Human Health Hazards from Broadcast Application of 0.005% Diphacinone Rodenticide Baits in Native Hawaiian Ecosystems
In the early 1990s, a coalition of federal and state agencies, NGOs, and private landowners in Hawaii agreed to pursue a Special Local Needs pesticide registration [24(c) FIFRA] for the aerial broadcast of a 0.005% diphacinone rodenticide for the control of rodents in native ecosystems. While there was recognition of the important role introduced rodents play in the decline and extinction of native species, there were concerns expressed about the potential non-target impacts of this technique. Over the next 10 years, numerous studies were undertaken to address specific non-target issues. This research, along with other published and unpublished research on diphacinone and its human pharmaceutical counterpart, Dipaxin, was compiled and analyzed in 4 hazard assessments (human dietary and drinking water consumption, aquatic and terrestrial non-target species) that comprise the foundation of Hawaii’s registration application. Hazards to humans and other non-target terrestrial organisms were evaluated in terms of dietary intake of contaminated food or water required before lethal or sublethal effects might be anticipated. Hazard to aquatic organisms was assessed according to traditional risk quotient methods employed by the U.S. Environmental Protection Agency. These assessments indicate the greatest human health hazard is to pregnant women drinking untreated stream water; however, even this risk is low. With a few exceptions, such as the Hawaiian crow, the ecological assessments indicate the acute risks to terrestrial or aquatic non-target species are minimal, even under the most conservative risk scenarios. However, there could be detectable physiological effects in birds exposed at sublethal levels. We believe that under proper supervision, this technique can be safely used in Hawaii, and elsewhere, to protect native species from the impacts of introduced rodents.
Current evaluations of the anticoagulant diphacinone for field control of introduced rodents in New Zealand include risk assessment with respect to non-target mortality, secondary poisoning, and environmental contamination. As non-target wildlife of rodent control operations, feral pigs may be exposed to vertebrate pesticides if they access toxic baits or scavenge the carcasses of poisoned animals. Feral pigs are also a significant resource for recreational hunters who harvest wild pork for food, hence the need to assess the risks of human exposure to diphacinone residues through feral pigs. Pen trials with domestic pigs were used to evaluate the potential for pig mortality through oral exposure to diphacinone and the residual persistence of diphacinone in pig tissues following a sublethal exposure. In the first trial, pigs were offered palatable food containing diphacinone doses of 12.5 mg/kg, 0.25 mg/kg/day for 3 days, or 0.5 mg/kg/day for 5 days. Significant elevations in coagulation time tests were measured 2 days after dosing, but these had returned to baseline values by 7 days. Two of the dosed pigs were euthanased due to lameness, which was accompanied by elevated prothrombin times and severe hemorrhage in a leg joint. In the second trial, pigs were dosed with 12.5 mg/kg diphacinone and then euthanased in groups for tissue sampling at Days 1, 4, and 10. Liver, muscle, and fat samples were analysed for diphacinone residues using an HPLC method. Data fitted to an exponential decay model estimated the hepatic elimination half-life as between 5.43 days (overall) and 14.12 days (terminal phase only). Half-lives of diphacinone in pig muscle and fat were 4.48 and 2.29 days respectively. A conservative withholding period of approximately 160 days is suggested before feral pigs should be taken for human consumption from areas where diphacinone baits have been used. This would minimize the likelihood of detectable diphacinone residues (≥0.02 µg/g) occurring in wild pork.
Probabilistic Model to Optimize Formulation and Baiting Strategies for the Pesticide CPTH (3-chloro-4-methylaniline hydrochloride)
A probabilistic model was validated for estimating avian mortality associated with the application of the avicide CPTH (3-chloro-4-methylaniline hydrochloride) to minimize sprouting rice damage in the southern United States. CPTH exposures for individual birds were predicted by random sampling from species-specific non-parametric distributions of bait seed consumption and CPTH residues detected on individual bait seeds. Mortality was predicted from the species-specific exposure versus mortality relationship. Individual variations in this response were captured in the model by Monte Carlo sampling from species-specific distributions of slopes and median toxicity values (LD50) for each bird. The model was used to evaluate the effects of formulation, bait preparation and application procedures on target and non-target mortalities. The results of these analyses indicate that: 1) decreasing the concentration of CPTH on the treated bait seeds from 400 to 300 μg CPTH/seed will improve bait performance by decreasing non-target mortalities, 2) the current dilution ratio of 1 treated seed to 25 diluent seeds is optimal and 3) preparing a bait seed product in which CPTH is homogeneously distributed throughout the bait seed mixture will significantly increase bait performance by increasing red-winged blackbird (target) mortality and decreasing mortality for savannah sparrows and meadowlarks (non-targets).
The Effect of Time on the Recovery of DRC-1339 Residues from Tissues Collected from Decomposing Mourning Dove Carcasses
Due to the slow-acting nature of the avicide, DRC-1339 (3-chloro-p-toluidine hydrochloride), birds may travel considerable distances following ingestion of lethal quantities of treated bait. Confirmation of DRC-1339 bait consumption in bird carcasses collected temporally and spatially removed from a baiting site has been problematic, particularly after a prolonged period of time, due to the decomposition of the carcass. To establish a temporal baseline for analytical methods developed for determining DRC-1339 residues in bird tissues, mourning doves were fed 2% DRC-1339-treated rice or control untreated rice. Birds were euthanized after 24 hrs. Bird carcasses were allowed to decompose for 1, 2, 7, 14, or 21 days at ambient temperatures (22.4 ± 0.7°C). GI tract and breast tissue samples were collected and solvent extracted for analysis by GC/MS for DRC-1339 residues. Residues could be detected in the GI tract samples up to 14 days after dosing. Linear regression analysis of the data indicated the possibility of detecting residues in GI tract samples for up to 23 days under similar environmental conditions for carcass decomposition. These results provide a time frame under which it is possible to confirm DRC-1339 bait consumption in birds by analyzing for residues in tissues from carcasses collected after a baiting operation.
Changes in Taxonomic Nomenclature and Conservation Status of Ground Squirrel Species: Implications for Pesticide Labeling and Use of Zinc Phosphide Pesticide Products
The taxonomic classification of species and their protection status have important pesticide regulatory implications, particularly regarding product label language. Changes in nomenclature may cause confusion for both pesticide applicators and regulators. Such changes may also result in the naming of new species in need of protection, or conversely species whose protected status may no longer be warranted. Over the past several years there have been gradual taxonomic changes within the genus Spermophilus. This change has resulted in splitting Townsend’s ground squirrel (Spermophilus townsendii) into 3 distinct species. In addition to S. townsendii, the Piute ground squirrel (Spermophilus mollis) and Merriam’s ground squirrel (Spermophilus canus) are now recognized. The Townsend’s ground squirrel, as now classified, is restricted to a small region in southwestern Washington. The species with the largest distribution, that was formally included in S. townsendii, is now the Piute ground squirrel (S. mollis). Zinc phosphide pesticide products are used to control a number of ground squirrel species including Townsend’s. However, based on the revised nomenclature, populations of the 2 new species (Piute and Merriam’s ground squirrels) may not be controlled using these zinc phosphide products under existing labels, even though those same populations were previously considered Townsend’s ground squirrels and could be controlled with zinc phosphide products. Potential conflicts with state and federal laws regarding protection of certain species must also be considered. The reclassification of Townsend’s ground squirrel recognizes new species and existing subspecies that are protected or are being considered for protection. In addition, subspecies of the Idaho ground squirrel (Spermophilus brunneus) are afforded various levels of protection under federal and state laws. A discussion of temporal taxonomy changes, geographic distribution, and conservation status of the “Townsend’s ground squirrel” complex and the Idaho ground squirrel is presented here to support the decision process needed to develop appropriate label language for zinc phosphide pesticide products.
The California Department of Food and Agriculture holds registrations for four grain-based anticoagulant rodenticides used in agricultural areas in California to control the California ground squirrel. These rodenticides contain either chlorophacinone or diphacinone as the active ingredient at 0.005% or 0.01% by weight, and are applied by either broadcast or spot baiting techniques. Using residue data from recent field studies, an ecological risk assessment was performed for non-target species potentially receiving secondary exposure through consumption of squirrel carcasses. The species of concern included five birds (American kestrel, burrowing owl, common raven, golden eagle, red-tailed hawk) and one highly sensitive mammal, the coyote. Risks to nontarget species were estimated using a risk quotient (RQ) approach, with RQ values calculated using species-specific daily exposure estimates and levels of concern derived from subchronic toxicity studies. Exposure estimates for the birds of concern ranged from 0.05-0.21 mg/kg bw/day for chlorophacinone and from 0.04-0.16 mg/kg bw/day for diphacinone. For chlorophacinone uses, RQs for birds ranged from 0.172-0.724. RQ values for diphacinone were 16-18 times lower. Based on the methodology used and using EPA risk criteria, the RQ data indicate de minimus risks for all avian receptors of concern. Exposure estimates for adult and subadult coyotes spanned a range from 0.009-0.028 mg a.i./kg bw/day depending on the use pattern. RQs for mortality and blood coagulation were generally near, or slightly above, a value of 1.0 for all of the use patterns evaluated; however, because of the conservative exposure assumptions and other factors, it is highly unlikely that ecologically significant effects on coyotes does or could occur due to use of CDFA’s anticoagulant baits. Wildlife incidence data and population modeling studies corroborate this. Based on the weight of evidence, it is concluded that use of CDFA’s rodenticides for spot and broadcast baiting will not cause “unreasonable adverse effects” on coyote populations or those of other predators/scavengers that feed on squirrel carcasses.
It was hypothesized that an inexpensive string-based tracking system could be developed to aid in the recovery of animals using tranquilizer dart delivery systems. Terminal velocity data were initially collected for 0.5-cc, 1.0-cc, 2.0-cc, and 3.0-cc conventional practice darts when fired from a .22-caliber cartridge-type dart gun at incremental distances of approximately 10-30 m. A commercially available archery string-based tracking system was modified and fitted to the dart gun. Power charges and pressure settings were changed in an attempt to achieve similar characteristics of darts when incorporating the string tracking system. During field testing, 10 raccoons were darted using the system, with 9 animals recovered. Ten white-tailed deer were darted and successfully recovered. All darts were readily recovered. Results of this study indicate the string tracking system is an inexpensive and reliable technology to facilitate the recovery of tranquilized animals and darts.
With the exception of trapping-based methods, quantification of wildlife populations has traditionally involved counts of animal sign (e.g., nests, scat, or calls) or cues (e.g., breeches by marine mammals) as indices, or counts of individual animals or groups (i.e., direct counts). In addition to the “naked” eye, researchers have used binoculars, spotlights, and more recently, night-vision and infrared technology (IT) to aid direct counts. However, IT has become a standard tool in a variety of practices (e.g., industrial, law enforcement, veterinary medicine) because any material with a temperature above absolute zero (i.e., -273.3°C) emits infrared light (i.e., the electromagnetic spectrum >0.70 μm), which can be quantified. The application of IT to wildlife management and research allows one to discern infrared emissions from target animals against background vegetation or habitat and, therefore, offers an improvement over traditional sighting methods. Use of IT in wildlife surveys also has inherent logistical requirements that must be considered in survey design. The purpose of this paper is to provide insight into the application of IT in wildlife management and research, particularly as related to quantifying populations of wildlife active during the night or periods of low-light conditions. Our objectives are to 1) briefly review methods and assumptions associated with conducting wildlife surveys, 2) review research and management efforts that have incorporated IT in surveys of wildlife populations, 3) discuss new opportunities for the incorporation of IT into wildlife research and management, and 4) provide guidance on purchasing IT. We suggest that IT, in combination with valid scientific sampling methods, can potentially increase the ability of wildlife researchers and managers to accurately estimate densities of wildlife populations.
Strategic management of brushtail possum populations in New Zealand is presently dependent on the use of a standardized trap-catch procedure for monitoring population trends. Where this has been used in the first few months after control, calculated rates of increase often far exceed known reproductive and dispersal rates, suggesting that trapping-based population indices immediately following control are biased low. We are investigating the problem by genotyping DNA extracted from possum fecal pellets and using matching genotypes in the ear tissue of trapped possums as a measure of trappability. We have used quantitative polymerase chain reaction (PCR) to determine the threshold of possum DNA required from fecal samples in order to obtain an accurate genotype (>99%) from field samples. This has enabled the removal of “allelic dropout” as a source of error in obtaining accurate genotypes from such noninvasive DNA samples. Validation tests were conducted on fecal samples collected from caged (i.e., identifiable) possums, and fecal pellets and ear tissue from trapped possums in the field. The tests confirmed that the sample collection and preservation procedures used resulted in accurate identification of possums from both types of sample material, although fecal pellets older than about 7 days were unlikely to yield sufficient DNA for amplification and genotyping. Genotyping of a large quantity of sample material collected before control, and at 1, 4, and 9 months after control, in 2 replicated field trials is proceeding and revealing information on the trappability of possums that survive control, and the contribution of immigration to the populations after control.
The successful management of vertebrate wildlife populations can be dependent on the availability of reliable monitoring methods, and, depending on the status of the species in question, effective methods of conservation or control. The brushtail possum, introduced to New Zealand from Australia, is considered New Zealand’s number one vertebrate pest. We assessed possum preferences for 3 types of visual lures and the potential use of this information for enhancing existing possum control technologies. Significantly more lures were interfered with by possums when the lures were associated with a luminescent strip, compared to lures that were plain white or UV-enhanced (P < 0.01 in both cases). In addition, more possums were killed when luminescent lures were attached to kill traps and bags of bait than when these devices were deployed without lures. This study has highlighted new information showing that luminescent lures could be a valuable new tool in the management of nocturnal marsupials, be they species considered pests (such as the brushtail possum in New Zealand), or species of conservation concern, such as many of Australia’s marsupial species.
Brown tree snake introduction to the snake-free island of Guam has severely impacted its native terrestrial vertebrates and economy. These nocturnal predators have extirpated forest birds, caused drastic reductions of lizards, and there is a major concern that snakes could be dispersed to other areas through Guam’s cargo transportation systems. Techniques to deter the spread of snakes include cargo inspection with detector dogs and live trapping using live mice as lures to reduce snake densities in cargo handling areas. Maintaining mice in traps is expensive, and an inanimate lure would be highly desirable. Oral baiting with dead neonatal mice (DNM) treated with acetaminophen is another technique being implemented for reducing snake populations. An objection to DNM is that they decompose and become putrid after 3-4 days. Consumption of 21 candidate bait matrices was compared to DNM in free-choice tests in individually caged snakes under laboratory conditions. Consumption of dead quail chicks and geckos was equivalent to DNM. Processed canned meat products, stew beef, and chicken were 30-50% as effective as DNM. Baits not consumed included dog blood, beef liver, and quail eggs. Under field conditions with live trapped snakes, consumption of 7 bait matrices was compared to DNM in 1-choice tests. DNM were preferred (55% consumption) over all other baits. Consumption of plastic lizards, chicken fat, and mealworms was 33%, 14%, and 13%, respectively. Odoriferous chemicals (n = 23), characteristic of decomposing animal flesh, were evaluated for their ability to attract snakes in the field. Chemicals were individually evaluated by placing them on tofu baits in PVC tubes (bait stations). Snake activity around the bait stations was monitored with infrared videography. Some of the 23 chemicals (i.e., L-methionine, 3-methyl-1-butanethiol) appeared to attract snakes to the tubes. However, no tofu baits treated with chemicals were consumed, whereas 100% of the snakes that visited tubes baited with DNM consumed the dead mice. These results, along with analysis of videos, indicate that chemicals may act as long distance lures but are insufficient for stimulating and initiating consumptive or appetitive search behaviors at close range.
Since 1996, the Internet Center for Wildlife Damage Management (ICWDM) has provided a clearinghouse for research-based information on mitigating wildlife damage. In July 2006, the ICWDM underwent a major revision to better serve the needs of its visitors. The site received a new URL, http://icwdm.org, layout, architecture, and content. Plans for further site enhancements include creating an image library, expanding content to include non-North American species, and encouraging interested parties to join us in eXtension.
Seventy-one Chinese ring-necked pheasants were radio-tracked in mixed crops in Sutter County, CA. Weekly survival of 39 wild (4 native and 35 translocated) versus 32 pen-reared birds were compared at 2 sites (~2,000 ha each) during the fall 1996 agricultural harvests. Pheasant survival after 1 week was wild 74% and 79% versus pen-reared 61% and 57% at the Meridian and Nicolaus sites, respectively. Thereafter, pooled sites survival was ~linear with ~1 wild bird dying every 2.8 weeks for 7 weeks and ~1 pen-reared bird death occurred every 4.7 days for 3 weeks. Several relocated and pen-reared pheasants joined wild flocks, and their survival improved with one of each harvested during the 1997 hunting season. Both survived >400 days. All affected pheasants changed their habitat utilization and movement ecology following the harvest of their primary cover and forage crop(s). Chi square analysis of habitat use by 30 wild and 19 pen-reared pheasants demonstrated habitat preferences were greater than its availability (P < 0.01) for milo (planted only in Meridian), weeds, and corn. Their preferences for alfalfa, beets, and safflower were equal to their availability. Rice was preferred when the fields were dry, but overall it was not preferred (P < 0.01). Also, orchards (cleared of ground vegetation for nut harvests) and fallow habitats were not preferred. Movement ecology data were separated by study site because of significant habitat differences. Home ranges (95% utilization areas) using the minimum convex polygon method to compare wild versus pen-reared pheasants averaged 74 and 67 ha at Meridian and 73 and 140 ha at Nicolaus. Daily rooster and hen movements averaged 295 m and 276 m for wild birds and 335 m and 382 m for pen-reared birds at the Meridian and Nicolaus sites, respectively. Results from the first fall pheasant study in California crops demonstrated they preferred the dynamic juxtaposition of grains and weeds for cover, shelter and forage with water. Twenty-nine pheasants (58%) demonstrated habitat preferences for grains– milo, rice, and corn. Pheasant survival was related to post-harvest habitat changes. Their home range, survival, and movements were very similar at both sites although the crop mosaic and habitat relationships were very different. These new results should be included in both public and private pheasant management practices.
The 21st century is witness to an unprecedented and rapid growth of human settlements, from urban centers to wilderness vacation resorts. Concurrent with this has been the growing tolerance and acceptance of many wild animals and humans for one another. This has created an expanding ‘zone’ of human-animal contacts, some number of which invariably result in conflicts. While the vast majority of our interactions with wild animals are undoubtedly benign, it is the conflict between wildlife and people that draws particularly close attention from the public. Animals viewed as vertebrate “pests” range from the small to the large, the timid to the fierce, and the benign to the dangerous. With respect to all is the issue that bridges both environmental and social concerns– what is the ‘right’ thing to do about resolving conflicts? Wildlife agencies in North America continue to stress traditional approaches to managing wildlife problems by focusing on regulated hunting, trapping, and poisoning. Yet contemporary human-wildlife conflicts have scientific, political, and moral dimensions that are not well addressed by those traditions. Controversy and polarization arise from differing ethics of how we ought to live with non-human animals. Wildlife protection interests argue that many common and current wildlife control practices, such as the drowning of “nuisance” animals, are ethically ungrounded. A practical ethic guiding our response to human-animal conflicts is, they argue, therefore needed. This ethics should inform “pest” control policy and management, as well as articulate a vision of our place in a mixed community of people and animals. This paper explores this need.
Urban wildlife control is a rapidly growing profession in which many practitioners apparently still come from a recreational or commercial trapping background. Perhaps for that reason, much of the “control” in resolving human-wildlife conflicts in cities and suburbs seems to revolve around the use of lethal traps to eliminate “problem” animals. Although some states allow relocation and most apparently allow for nuisance animals to be released on site, the extent to which these practices occur is little known. Further, the biological impacts of continual trapping cycles on urban wildlife populations remain little known as well. An alternative approach to trapping is to exclude problem animals, as is the generally accepted protocol with bats, taking care to avoid separating young from their mothers, or employing techniques to reunite mother and young through a carefully crafted reunion strategy. AAA Wildlife Control is a large wildlife control business based out of Toronto, Canada, that employs almost exclusively an exclusion-reunion strategy. This paper addresses the rationale for that approach and the general strategies the company uses for common problem species. Exclusion-reunion is arguably the most humane and biologically sound approach to wildlife conflict resolution, at least from the animal’s perspective, but questions will be raised about the potential transfer of “problems” from one site to another. These and other implications of this approach are raised and discussed based on multiple years of customer service.
A billion-plus human population, agriculture, and development are shrinking and degrading the habitat of many of the 1,200 bird and 500 mammal species of India. With humans and herbivores competing for the same resources, many of them are becoming pests on crops. The granivorous birds depredate on selected cereals, sunflower, groundnut, and oil palm. Guava, grape, apple, sapota, pecan, pomegranate, and pineapple are damaged significantly by frugivore birds. Amongst vertebrate pests, rodents are the most destructive. A dozen species, viz. Rattus rattus, Bandicota bengalensis, B. indica, Millardia meltada, Mus booduga, M. platythrix, Mus musculus, Tatera indica, Meriones hurrianae, Funambulus pennanti, F. palmarum, F. tristriatus, and Hystrix indica are serious pests. Cereals, pulses, oil seeds, vegetables, fruits, and plantation crops are damaged considerably. Sown seeds, seedlings of maize, sorghum, sunflower, groundnut, red gram, tender coconut, oil palm, cardamom, and cocoa are depredated much more. Other vertebrate pests of significance are Pteropus giganteus, Cynopterus sphinx, Rousettus leschenaulti (bats), Boselaphus tragocamelus (Nilgai), Elephas maximus (elephant), Macaca mulatto, and Semnopithecus entellus (monkeys). Sporadically, other langurs, sloth bear, wild boar, hare, golden jackal, and peacock become pests. This paper reviews the lethal and non-lethal methods of managing this wide of array of vertebrate pests.
Cottontail rabbits are a serious problem in Southern California. Of particular concern is the damage they do to ornamental plant and tree nurseries. Rabbit browsing reduces plant quality, kills containerized plants, and damages irrigation systems. Although anticoagulant baiting for cottontail rabbits is legal in California, growers should also consider multiple integrated tactics for rabbit damage control. This project employed GPS mapping technology to locate the occurrence of rabbit damage and correlate it with irrigation type, container, planting density, canopy width, and canopy height. GPS was also used to monitor the impact of experimental strategies to reduce rabbit damage. Strategies to reduce rabbit damage included the use of protective covers on irrigation tubing, exclusionary fencing, and trapping. Radiotelemetry was used to confirm the location of suspected rabbit harborages within the nursery. GPS results indicate that 1.27 to 1.9-cm (½ to ¾-in)-diameter irrigation line covers were effective in reducing rabbit damage to the irrigation system. Exclusionary fencing using erosion-control silt fencing acted as an excellent temporary barrier to protect individual growing areas and groups of planting beds, but it was found to be impractical for many nursery situations. Rabbit catch rates increased when traps were used in conjunction with drift fences. General tactics recommended to container nurseries based on these study results include: protecting and modifying irrigation systems, use of exclusionary fencing, trapping in conjunction with drift fencing, and modifying known rabbit harborages where possible.
Cottontail rabbits cause serious damage to ornamental plant production in Southern California. We used a 300-acre Southern California tree nursery as a cottontail CDFA vertebrate pest study site. We evaluated the relationship between nursery practices and the incidence of rabbit damage. GPS technology in combination with GIS software was employed to map and ascribe descriptive characteristics to the growing practices within each nursery bed. To understand the pattern of rabbit damage to irrigation, handheld GPS units were utilized by nursery staff conducting irrigation repair to assess damage caused by vertebrate pests. The waypoints taken by the irrigators superimposed on the map of the nursery had numerous benefits to the study, including demonstrating which growing conditions were most vulnerable to rabbit damage and elucidating if measures to reduce rabbit damage were successful. The same methodology may be helpful to researchers in many IPM fields.
Wildlife agencies face the complex, often difficult, challenge of managing nuisance wildlife complaints. State agencies are under increasing pressure to provide better training for individuals in the private sector who provide such services. In July 2002, New York State (NYS) passed a law that mandated both training and documented proficiency for all nuisance wildlife control operators (NWCOs) who charge a fee for service. A team of NYS Department of Environmental Conservation (DEC) and Cornell Cooperative Extension (CCE) staff was organized to produce a curriculum and certification exams. The goals were to enhance the skills and professionalism of both current NWCOs and new license applicants, while maintaining a diverse array of operators that could provide the many levels of service required by various publics. Additionally, the training manual was designed to be a reference for DEC and CCE staff and others who are interested in nuisance wildlife control. The central philosophy of the manual was integrated wildlife damage management (IWDM), referred to as “best practices” in the manual. A best practice was defined as an effective method for solving a nuisance wildlife problem that minimizes risks to the environment and promotes human safety and well-being. Development of the curriculum (both hard copy and electronic versions) and the associated electronic test bank involved extensive and comprehensive research, reviews, and pilot testing. The curriculum and licensing examinations have been implemented in NYS, and the curriculum has won three different awards from state wildlife, extension, and stakeholder associations. Currently, a NWCO curriculum for the eastern United States is being developed, and it will provide a comprehensive, science-based, peer-reviewed training that satisfies stakeholder-identified needs. This regional curriculum fills an important gap that would otherwise likely be addressed by each state individually. The credibility of the training manual and certification exam will likely prove beneficial to NWCOs as the public becomes aware of this new process. The emphasis on best practices and the responsible treatment of wildlife will also resonate with the public.
Three-Man Thermal Team (T.T.T.): An Advanced Technique for Control of Overabundant or Nuisance Wildlife
The Three Man Thermal Team (T.T.T.) is a technique developed within the Fairfax County Virginia Integrated Deer Management Plan in cooperation with the Fairfax County Police Department’s Special Weapons and Tactics (SWAT) unit for control of overabundant white-tailed deer populations within a suburban/urban setting. The technique utilizes a combination of specialized equipment including a hand-held thermal imager, a laser pointer, a 6-million-candlepower MaxaBeam™ searchlight with focusable beam, and a suppressed rifle. T.T.T. allows targeted animals to be located in total darkness. With the use of a night vision or thermal scope in lieu of the light, the entire operation can be conducted in darkness. While this technique was specifically designed for deer, it can be easily adapted for other species.
Invasive Frogs’ Influence on Lowland Forest Arthropod Communities and Ecological Processes in Hawaii
We conducted an enclosure experiment at two lowland sites on the eastern side of the Island of Hawaii for 6 months (September 2004 to February 2005) to determine the effect of Eleutherodactylus coqui on 1) three invertebrate communities (aerial, herbivorous, and leaf litter), 2) nutrient cycling rates and leaf litter decomposition rates, and 3) native and non-native plant growth rates. E. coqui was found to reduce all invertebrate communities at one study site, while the other site did not have any difference with treatment. At both sites, herbivory rates were lower in the presence of E. coqui than in their absence. At both sites, E. coqui was associated with increased NH4+ in leaf washes, increased K, Mg, N, and P concentrations in the leaf litter, and increased decomposition of leaf litter. P. cattleianum had more new leaves in presence of the E. coqui than in the absence of E. coqui across sites. Non-native plants had higher survivorship than native plants. In summary, invertebrate community responses to E. coqui differed by site but ecological processes responded similarly across sites. Path analyses suggest that the E. coqui increases leaf litter decomposition and non-native plant growth rates by making nutrients more available to microbes and plants. These findings are of concern in Hawaii, where E. coqui can potentially affect the 44 endangered invertebrates and potentially increase non-native plant growth.