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 20, 2002
I discuss the concepts of trust and credibility in relation to the wildlife profession. Using the recent Canada lynx monitoring controversy in Washington State, I demonstrate that innocent actions have consequences that erode trust. Effective natural resource management requires that we, as individuals, agencies, and a profession, maintain high levels of credibility with the general public. As scientists and educators (and as opposed to elected officials), we enjoy relatively high levels of trust. It is critical that we maintain what we currently have, and that we develop programs and strategies to increase our credibility and the trust obligation that society requires from us.
The Nevada Department of Agriculture acquired the authority to control vertebrate pests of agriculture and public health in 1975. Prior to the Department becoming involved in vertebrate pest control, agricultural producers did not have ground squirrel baits which were very effective. The Department examined products used in surrounding states and due to the effectiveness of sodium monofluoroacetate fresh cabbage baits used in Modoc County, California, began using strychnine cabbage baits. Strychnine was chosen as a toxicant rather than sodium monofluoroacetate because it was thought to be less “toxic” politically. Fresh chopped cabbage baits were initially broadcast above ground in swaths or near active ground squirrel burrow openings. Due to the prohibition of above-ground uses of strychnine which resulted from a 1988 U. S. District Court ruling, the Department changed the labeling of its strychnine paste concentrate. Ground Squirrel (and yellow-bellied marmot) baiting directions now require bait to be placed 6 inches or more into burrow openings. The change in application procedure reduced the effectiveness of chopped cabbage bait, however it still surpasses the effectiveness of grain based baits due to the attractiveness of the cabbage to ground squirrels in Nevada. Baits are usually prepared on site by the producers who apply it immediately after formulation. One application in early spring prior to the emergence of juveniles is the optimum time for baiting. Follow-up applications may be made on surviving ground squirrels or when ground squirrels migrate in from other areas later in the season.
We conducted field trials during 2000 to compare the effectiveness of 0.4% strychnine commercial ready-to-use (RTU) hull-less oat and canary seed (CS) bait to control Richardson’s ground squirrels (Spermophilus richardsonii) and during 2001 to compare the effectiveness of RTU and freshly prepared from concentrate (FFC) hull-less oat bait. Each study was conducted at 30 locations in ungrazed pastures and unharvested forage crops in southern and central Alberta from mid-June to mid-August. Effectiveness was measured using pre and post treatment visual, dead and in 2000 active burrow counts. In both trials visual counts increased with daily maximum temperature (P < 0.05), decreased with rainfall intensity (P < 0.001) and were not affected by wind speed or start time (P > 0.05). The 2000 field trials indicated that adjusted visual counts of ground squirrels were significantly lower than controls in CS than RTU baited plots (77.6% and 59.6% reduction, respectively, P = 0.002) and the mean number of dead ground squirrels was higher (6.43 and 2.13, respectively, P < 0.001). Additionally, there were significantly (P < 0.001) fewer re-opened holes by ground squirrels in the RTU (41.6%) and CS (71.7%) treated plots compared to control plots. All 3 measures indicated greater effectiveness using canary seed than hull-less oat bait. The 2001 field trials indicated that adjusted visual counts of ground squirrels were significantly lower than controls in FFC than RTU baited plots (92.7% and 65.6% reductions, respectively, P < 0.0001) and the adjusted mean number of dead ground squirrels was higher (4.28 and 1.21, respectively, P < 0.0001). Both measures indicated greater effectiveness using freshly prepared from concentrate than manufactured ready to use hull-less oat strychnine baits. In conclusion, we advocate further research into freshness as bait freshness may be the single most important factor affecting effectiveness
Many fossorial species of wildlife cause damage in a variety of land-use settings. Research of these species is challenging because of the complications associated with working underground. Traditional methods of conducting research on fossorial rodents in their natural environments are expensive, labor intensive, and invasive on the landscape. More innovative and effective methods of doing research underground are needed. We evaluated a burrow-probe camera for viewing inside the burrows of California ground squirrels (Spermophilus beecheyi) as part of an anticoagulant baiting study. It was useful for locating carcasses as well as for collecting information on live squirrels and non-target species. We also used burrow cameras to aid in on-going studies of black-tailed prairie dogs (Cynomys ludovicianus) and evaluated their utility in the burrows and dens of other mammals along the front range of Colorado. We will discuss our evaluations of burrow cameras and applications for their use in wildlife damage research.
The 2½-day Colorado Front Range Prairie Dog Technical Workshop was held in Fort Collins, Colorado, February 27-March 1, 2001. The workshop attracted about 250 attendees, mostly government personnel. Black-tailed prairie dogs (Cynomys ludovicianus) present numerous challenges to landowners and resource managers because they are considered a rare and important ecosystem component, but at the same time they can cause various kinds of damage and pose a disease hazard to humans and their domestic animals. Invited speakers updated the participants on the topics of prairie dog biology and ecology, legal status and distribution, socio-economic issues, management techniques and strategies, and current research. Special topics such as plague management and black-footed ferret re-introductions were also addressed. Several panel discussions on management challenges and options were held. Various perspectives were presented and there was considerable interaction on these volatile issues. There was a field trip to local prairie dog colonies to view and discuss conflicts and management options. In this paper, we summarize some of the key topics and perspectives brought up at the Workshop, in order to provide a broad synopsis of this highly contentious arena of human-wildlife conflict.
The northern pocket gopher (Thomomys talpoides) is considered a major pest in haylands, particularly alfalfa, and surrounding crops and shelterbelts of western Canada. Although poison baits are often used with the objective to quickly reduce pocket gopher populations over large areas, recent investigations in western Canada have demonstrated that they were ineffective in reducing and controlling pocket gopher populations in haylands. This paper identifies the elements of an effective pocket gopher control program and demonstrates that, with a proper strategy to lay out killing traps in spring to remove breeders-of-the-year, and to intercept invading pocket gophers, trapping is the most effective method to control northern pocket gophers. This paper also describes an effective trapping program and identifies research needs to increase capture efficiency.
The nutria (Myocastor coypus) is a large semi-aquatic rodent that was introduced throughout much of the world as a means of increasing the fur market in the first half of the 20th Century. Although not considered a pest in their native range of South America, nutria presence elsewhere has often met with greater detriment than benefit. Nutria have damaged crops, marsh vegetation, and water control structures. Nutria damage has been described for decades, yet science is now better defining values provided by marshes that are prime habitat for many mammalian, avian, reptilian, and amphibian species as well as flora. The uniqueness of the marsh and coastal habitats is in jeopardy of being so damaged as to make the cost of repair astronomical. Nutria foraging often causes current re-vegetation projects to fail unless exclosures are constructed. We review potential methods to control nutria damage in Louisiana. Techniques discussed include: incentive (bounty) payment, chemical control (toxicants), incentive-bonus, induced infertility, trapping, controlled hunting, and chemical repellents. We rank these by feasibility of implementation and their probability of success.
Rodent damage research in Hawaii has evolved in response to shifts from large-scale monoculture agriculture, such as sugarcane, to cultivation of diversified high-value specialty crops, such as export ornamental nurseries and forestry products. Recent findings and renewed conservation awareness of the impact of predators, especially rodents, as important limiting factors of many of Hawaii’s endangered avifauna have stimulated increased efforts to reduce rodent depredation in conservation areas and other natural resources. Some of the early tools developed in agriculture have been incorporated and successfully used for protecting non-agricultural resources and new methods have been developed for current problems. This paper summarizes the rodent research that the National Wildlife Research Center’s Hawaii Field Station has conducted over these years of changing economic times and priorities.
Management of commensal rodent populations requires greater emphasis on long-term planning and maintenance of urban infrastructure. Integration of engineering and biological principles is necessary to effectively accomplish this. Design engineering provides opportunity to include rodent control features within the infrastructure being built. Construction-period rodent control helps prevent community impacts and keep facilities from being completed with pre-existing rodent problems.
We conducted a comprehensive economic analysis of rodent control in swine production facilities. An interdisciplinary working group was assembled to identify all necessary input variables and values associated with rodent damage and control. We incorporated data from production models, scientific literature, product literature, producers and personal experience into an interactive STELLA systems model. The model generates cost-benefit analyses and predicts outcomes of various levels of control of house mice for site-specific swine confinement facilities. We developed a website on rodent control (http://rodent.swine.unl.edu/) to promote use of the model, increase producer awareness of the costs associated with house mouse damage, and provide information on integrated strategies for managing rodents. Although the model is relatively robust and comprehensive, we noted important gaps in research-based information, particularly associated with the economic impacts of rodents in disease transmission, feed contamination, food safety, quality assurance, and human dimensions. We will continue to improve the model and website as new information becomes available.
The Cuban hutia (Capromys pilorides), known locally as the banana rat, is a large rodent native to Cuba. Endemic to the West Indies, most species of hutia are rare or extinct because of over-harvest, exotic species introductions, and habitat modifications by humans. An exception is the U.S. Naval Base at Guantanamo Bay, Cuba, where the Cuban hutia is very common and is responsible for a variety of damage and conflicts. Conflicts with humans include damage to landscaping, gnawing through cables, damage to vehicles, and the accumulation of large amounts of feces in residential areas. Additionally, hutia are primarily herbivores and botanists have documented substantial damage to native vegetation with little subsequent regeneration of many plant species. Current management focuses on population reduction by shooting and some trapping, followed by euthanasia or relocation to remote areas. Although there is little published information on the Cuban hutia, this paper presents a literature review, population survey data (1999-2000), and biological data from a sample of hutia collected in May 2001. It appears that the hutia, the largest native mammal in Cuba, is quite prolific and well adapted to exploit most habitats and plant foods. Some considerations, including advantages and disadvantages, of potential management techniques (habitat modification, exclusion, trapping, shooting, and toxicants) to reduce damage and conflicts with hutia are presented. Finally, several areas of additional data or research needs are identified.
About 70% of the current energy intake of the human population in southeast Asia is met by rice. Rats, especially the ricefield rat, Rattus argentiventer, cause significant pre- and post-harvest losses in rice-based agro-ecosystems of southeast Asia and therefore require appropriate management. Current management practices focus on culling animals when populations are high and after significant damage has already occurred. The use of legal and illegal poisons poses a considerable threat to non-target species and humans. This is of particular concern in regions where rats are often consumed by humans to provide an important protein supplement to their diet. During the last seven years, CSIRO’s rodent research group has tested and refined several methods aimed at decreasing pre-harvest rodent damage in cooperation with the Indonesian Research Institute for Rice and the Vietnamese National Institute for Plant Protection. These methods include exclusion of rats by fencing and physical control by trap-barrier systems with lure crops. The effects of these technologies were investigated regarding the regulation of rat numbers (physical control), damage (exclusion, physical control) and yield (physical control). The results are promising, indicating yield increase, of up to 20% in some cases. Integration of these methods with improved field sanitation, crop synchronisation and more efficient timing of other physical methods of control should result in pronounced increases in yield and improved cost effectiveness. Our approach is contingent on a strong understanding of the ecology of specific rodent pests. Measures of success besides decrease in rat numbers and damage are an increase in farmers’ net income through yield increase and a decrease in the use of chemicals. Pros and cons of these methods in different economic and cultural environments are discussed.
Foraging by rice-field rats (Rattus argentiventer) can significantly reduce rice harvest. Rat populations are cyclic responding to season and crop maturity. Rat location also reflects the crop cycle. A study conducted near Sukamandi, Indonesia described rice-field rat burrow systems and patterns of use, and assessed demographics of rice-field rats found in burrows adjacent to rice fields. Burrows ranged from simple short tunnels to complex systems. Most simple systems consisted of a straight tunnel approximately 75 cm long. Mean tunnel length of more complex systems was approximately 300 cm, but a few contained tunnels up to 700 cm. Burrow systems had between 1 and 5 entrances, with 0 to 8 choice-points within the system. A choice-point was defined as any place within the system where the animal could choose a different path (e.g., Y in the tunnel, nest). Number of chambers within systems also varied, ranging from none to six. There was no correlation between rat activity within a system, measured by the closed-hole method, and complexity of the system. Long-term monitoring suggested both male and female rats occupied burrow systems along rice banks, except relatively short periods during spring (March, April) and early fall (September) when burrows were used almost exclusively by females. These periods appear to correlate when high numbers of female rats are gestating and lactating.
Cane-rat/grasscutter (Thryonomys swinderianus Temminck) is both a pest of crops in Nigeria and a source of animal protein especially in Western and Central Africa. Cane-rat damages several crop species including rice (Oryza sativa), maize (Zea mays), cassava (Manihot spp.), yam (Dioscorea spp.), sweet potatoes (Ipomea batatas), groundnut (Arachis hypogaea), pineapple (Ananas comosus), sugarcane (Saccharium officinarum), guinea corn (Sorghum bicolor), millet (Eleusine coracana) and palm tree (Elaeis guineensis), in the savanna and in the rainforest ecological zones of Nigeria. Rice and cassava were found damaged in both wet and dry seasons of the year. Maize, millet, and guinea corn were usually damaged during wet periods. The annual production of meat of cane-rat exclusively from hunting in Benin is valued at 500 tons, this being about 200,000 heads and does not represent more than 65% of the estimated demands of the Beninese populations. Total revenue from bush meat in 1997 in Ghana was $247m, while cane-rat accounted for 70% of this. The cane-rat can be reared in captivity with minimal capital outlay. Its high prolificacy and fecundity makes it a meat source of high potential to bridge the gap in animal protein deficiency which currently averages 4.82g/head/day in Nigeria as compared to a recommendation of 35g/head/day for an adult. During the pesting activities of cane-rat, they were readily cropped in an attempt to control the pesting problems. The animals were cropped in farmlands during the rainy season and from wild land during the dry season. Fencing, trapping, dog hunting, shooting, clubbing, pitfalls, and use of charms were some of the various methods used by rural people to control pesting activities of cane-rat on farms. There is need to develop both a strategy for effective control of the cane-rat and improving the management in captivity for breeding purposes.
Developing methods to manage conflicts between humans and birds -- three decades of change at the USDA National Wildlife Research Center
As the U.S. population has increased and the number and nature of problems caused by wildlife has changed, the focus of research conducted by USDA APHIS National Wildlife Research Center (NWRC) scientists has evolved to meet changing demands for effective solutions. This paper summarizes changes in the focus of NWRC Bird Research Program as reflected in 1) three surveys to determine priority research needs of the Wildlife Services (WS) program, 2) NWRC research literature produced in each of three decades since 1970, and 3) the focus of current research in the NWRC Bird Research Program. Many research needs of the WS program were consistently expressed in three programmatic research needs assessments (RNAs) conducted in 1989, 1996, and 2001, while others changed as new bird-human conflicts emerged. Blackbirds, starlings, waterfowl, gulls, wading birds, and cormorants were listed in all three RNAs, while pelicans and vultures are more recently expressed as a priority research needs. The major emphasis of NWRC bird research publications over the last three decades has been related to blackbirds, starlings, and grain crops. Songbirds also were a subject of many research publications during each of the last three decades. Waterfowl, gulls, and cormorants, as well as aviation, aquaculture, and endangered species, were subjects of increased research focus at the NWRC during the 1990s.
We conducted studies from 1994 to 1999 in eastern South Dakota to determine the best strategy for baiting spring-migrating blackbirds. From 26 March to 14 April, male and female red-winged blackbirds made-up 61% and 17% of the roost population, respectively. After the 14th of April, the population consisted of 32% male and 49% female red-winged blackbirds. Blackbird migration in eastern South Dakota generally ended by late April. Habitat use studies conducted in March and April 1994, 1995, and 1998 showed that blackbirds used corn stubble for foraging and woodlots/shelterbelts for loafing. We concluded that bait plots located in corn stubble adjacent to wooded areas could attract large numbers of red-winged blackbirds during spring migration.
Bird control often entails the use of sound to disperse birds from croplands or other sites. Little information is available concerning the sound levels produced by noise-making devices or the effective area of coverage. In 1998 and 1999 we measured the sound levels of American crow (Corvus brachyrhynchos) distress calls produced by 2 models of a commercially available broadcast unit. With the units set up at different heights (0.9 to 4.9 m) in an open area or in an almond orchard, we used a sound meter to measure sound levels at distances of 1 m and 15 m, and then at 15-m intervals out to a distance of 90 m from the speakers. Sound levels decreased from about 102 dB at 1 m down to or nearly to background noise levels at a distance of 90 m. Sound levels from a unit set up to broadcast at a 4.9-m height through the orchard canopy were lower than for a unit set up at a 0.9-m height broadcasting under the canopy. Sound levels from a unit set at the 0.9-m height in the open were greater than those from the 0.9-m setup under the canopy only at a distance of 90 m. We set up a broadcast unit at various roadside locations in Yolo County, California, to determine the distance over which crows heard and reacted to the broadcast calls. Upon activation of the unit, we scanned the surrounding area for any crows flying from their perches. When crows reacted to the call we recorded the distance to the site of origin with a laser rangefinder and the number of crows. We also recorded the distance and number as above for any 2nd or 3rd flocks responding. We broadcast the calls on 11 days and on 27 occasions crows responded, typically by flying up from their perches, sometimes flying overhead, and then flying away. The average distance for the 1st flocks was 142 m + 73 SD (range 22 - 275 m). On 7 occasions 2nd flocks responded from an average distance of 174 m + 110 SD (range 71 - 312 m). On all but one occasion the 2nd flocks originated from a more distant location than the associated primary responders. We observed one instance of a 3rd flock responding. Fourteen (51.8%) of the 27 primary responses were from distances >122 m, about the distance at which the sound levels from the broadcast unit drop to background levels. These data indicate crows detected sounds from the broadcast units at distances greater than suggested by the sound meter. Using the average distance of 142 m for the 1st flocks responding, we calculated crows in a 6.3 ha open area could hear the broadcast calls. Using the maximum distances we observed of 275 m for 1st flocks and 312 m for 2nd flocks, we suggest that under some conditions crows within open areas of nearly 24.3 ha and 30.4 ha, respectively, heard the calls or responded to other crows hearing the calls.
The U.S. Fish and Wildlife Service (USFWS) and the Nevada Division of Wildlife (NDOW) have both observed an increase in the population of common ravens (Corvus corax) throughout Nevada. This increase is suspected to be the result of, at least in part, supplemental feeding sources (landfills, road kills, feedlots, etc.). The increase is of concern to wildlife managers because ravens are known nest predators, and in excessive numbers they could adversely affect a wide variety of game birds, including the sage grouse (Centrocercus urophasianus). During the spring in both 2000 and 2001, Wildlife Services (WS) was contracted to manage raven numbers in a critical sage grouse nesting area in northern Washoe County. The primary management tool used by WS was the registered avicide DRC-1339, because it can be selectively used on birds that feed on eggs. A prepared DRC-1339 solution was injected into hard-boiled chicken eggs and placed in artificial nest sites located throughout the project sites. Ravens foraging in the nesting area for sage grouse eggs found and consumed the treated eggs and died, thus selectively removing the nest-raiding birds from the immediate area of the grouse nesting sites. No long-term effect is anticipated on the raven population, because treated eggs were placed out only in the immediate area of the nesting grouse and only during the brief nesting period. The possibility of secondary poisoning resulting from DRC-1339 use is considered unlikely because the active ingredient, 3-chloro-p-toluidine hydrochloride, is broken down into a non-toxic substance and expelled prior to the bird expiring. Consumption of DRC-1339 results in death due to renal failure in avian species. Ravens found after treatment were monitored for the presence of West Nile virus titers.
Information is presented concerning the use and registration status of Avitrol Corporation products for pest bird management. These products have 4-aminopyridine as the active ingredient. Data were gathered from current U. S. Environmental Protection Agency (EPA) registration status, state and company files. Various Avitrol products are registered in all 50 states and in Canada.
Bird control in agriculture is an age-old problem. Techniques range from various types of lethal control to hazing and exclusion. Netting is used effectively in several forms of agricultural bird control. In grapes and blueberries, netting is applied by the row or in an overhead canopy fashion. Netting is also used in aquaculture to eliminate damage from wading birds. No one debates the effectiveness of net, however, the application and retrieval has been so problematic as to make the process not worth pursuing. In recent years, significant advances have been made in the field of mechanized net application and retrieval. These advances combined with innovative applications in aquaculture and other industries bring the use of netting for agricultural bird control to a new level of effectiveness.
As land-use patterns change and urban populations surge into previously undeveloped areas, wildlife conflicts inevitably increase. Of increasing concern are problems associated with black (Coragyps atratus) and turkey vultures (Cathartes aura), two species that have shown the capacity to adapt readily to human activities. Previously, we demonstrated that roosting vultures can be successfully dispersed from communication and broadcast towers by hanging a vulture carcass or taxidermic effigy in the structure. Here, we extend that method to situations where vultures are affecting residential property and agricultural resources. At 4 of 8 study sites where vulture damage to property was a concern, damage was eliminated by hanging a carcass or effigy in trees where the vultures roosted. At the other 4 sites, where the roost was inaccessible, vulture damage ceased after carcasses or effigies were hung on or near the property directly affected by the birds. After vulture activity had been reduced, the effigies or carcasses at 4 of the 8 sites were replaced by Canada goose (Branta canadensis) decoys painted to resemble vultures. Vulture activity continued to be suppressed at those locations. At 1 of 2 study sites where depredation to livestock was a concern, vulture activity at a pig breeding facility was reduced 90% after a taxidermic effigy was installed overhead. At the other site, where depredation of cattle and calves by vultures was a concern, a nearby roost of 800 birds was dispersed using effigies; the effect upon depredation has yet to be determined. Our investigation to date has found the hanging of vulture carcasses, taxidermic effigies, and decoy effigies to be effective for the management of vulture problems in a variety of situations. This nonlethal vulture management approach will not be appropriate or effective in every case, but its use should be considered, particularly where roost dispersal is desired.
We evaluated the effectiveness of Allsopp Helikites® as a gull (Larus spp.) deterrent at loafing and nesting areas and as a bird deterrent in a sunflower field. In 1998, a 10-day trial was conducted at two 0.5-ha ponds at the Erie County, Ohio landfill (EC) and a 2-week trial on two 0.1-ha plots on the Tru-Serv Corporation (TSC) warehouse roof in Cuyahoga County, Ohio. Also in 1998, a 5-week trial in a sunflower field was conducted in Erie County, Ohio. In 1999, a 24-day trial was conducted at the Service Liqueur Distributors (SLD), Inc. warehouse roof, 1.6 km from the Albany, NY landfill. At the EC landfill the mean number (±SE) of ring-billed (L. delawarensis) and herring gulls (L. argentatus) on the treated pond decreased (P < 0.05) from 421 ± 292 to <1 after Helikite deployment, whereas the mean number of gulls on the untreated pond increased (P < 0.05) from 73 ± 135 to 412 ± 456. At the TSC roof, the herring gull nest density differed (P < 0. 01) between areas covered and not covered by Helikites. Nest density under Helikites decreased from 41/ha to 18/ha within 7 days of deployment. Nest density in areas not covered by Helikites increased from 23/ha to 42/ha within 14 days of deployment. At the SLD warehouse, when Helikites were not in place, the mean number (± SD) of gulls on the roof was 41 (± 38). When Helikites were in place, no gulls were observed on the roof at any time. Mean damage to sunflower heads remained similar in the Helikite-treated and untreated plots until the last week of measurement when damage in the untreated plot increased to 26% seed loss/head whereas damage in the treated plot remained at about 8%. Helikites are a high-maintenance tool and are limited by weather conditions, electrical lines, and structures that can damage Helikites. We conclude that Allsopp Helikites have the potential to deter gulls from preferred loafing and nesting areas and could be included as part of an integrated management program to disperse gulls. Further research on Helikites is needed to determine optimum deployment heights, habituation rates for gulls and other species, and the actual sphere of influence of the kite for various species.
Border Collie Rescue (BCR), in cooperation with the Dover Air Force Base (AFB), conducted a series of field trials to test the efficacy of utilizing radio-controlled models (RCs) (aircraft and boats) in dispersing several species of birds from troublesome locations around the Dover AFB environment. Results of these trials suggest that RCs can be used to effectively harass gulls, black vultures, ducks, and geese from difficult areas, though there are a number of limitations and contraindications that must be taken into account when determining the value of instituting a harassment program utilizing RCs. Though use of border collies in its wildlife management program had eliminated the majority of bird hazards at Dover AFB, a few troublesome areas and species remained, particularly those birds that were located in areas inaccessible to the dog (e.g. large quarries with heavy machinery, soaring vultures). Radio-controlled aircraft were highly effective in dispersing large flocks of loafing gulls, black vultures soaring in thermals and passing through the airfield environment, as well as flocks of ducks and teal feeding and resting on open bodies of water. They were also partially effective at discouraging transitioning gulls and geese from utilizing the airspace over the base, as well dispersing gulls feeding on earthworms on runways and taxiways, though several environmental and operational variables determined success. Radio-controlled aircraft were entirely ineffective in dispersing Canada geese from open water. Coordinated effort with a radio-controlled boat, however, solved this limitation and proved to be an effective means of eliminating the Canada goose presence from large bodies of water.
The monk parakeet (Myiopsitta monachus) is native to South America but has become established in several locations throughout the United States through purposeful and accidental releases. The species is unique among parrots in that it is not a cavity-nester, but instead it builds a bulky nest structure of sticks. Often, in its native range and in the United States, the parakeet selects a electric utility structure as a nest site. Material from the nest then can cause short-circuits that result in damage to the utility structure and a subsequent power outage. In south Florida, monk parakeet damage and associated outages have increased substantially in recent years. Although the full costs associated with the damage and the outages are not known, it is evident that current methods to manage the problem are inadequate. In 2001, to address the need for more effective management methods, Florida Power and Light Company initiated a project to identify and investigate new, potentially useful management alternatives. In this paper, we review what is currently known regarding the impacts of monk parakeets to electric utilities and we discuss the status of research to develop new methods to reduce these impacts.
Vision is a primary and highly developed sensory pathway in birds. Light, both diffuse and wavelength-specific (e.g., as produced by lasers) has recently been demonstrated as a potential means of effecting changes in timing and consistency of flock response to an approaching vehicle (simulating an aircraft) and as an avian dispersal method. However, in experiments to date, the effectiveness of light in eliciting an avoidance or dispersal response in birds has varied by species and context. To effectively use light in managing avian conflicts with humans, a better understanding of the complexities of avian retinal physiology relative to phototaxic responses to the environment is necessary. My objectives are to provide an overview of research pertaining to 1) anatomical features of the avian eye and 2) the ecological implications of retinal wavelength sensitivity, and 3) discuss the application of light for resolving avian conflicts with humans. I also suggest that future evaluations of light-based management methods for birds should include integration of aposematic colors and color pattern treatments for seeds and in combination with chemical repellents, as well as quantification of the effects of light wavelength, pulse frequency, and beam configurations of lasers, and aircraft-mounted light in eliciting avian dispersal and avoidance behavior.
Peafowl are an introduced species on Southern California’s Palos Verdes Peninsula. Frank Vanderlip, Sr., the area’s developer, brought this non-native species to his Rancho Palos Verdes estate. While the exact year is not known, it is likely that the introduction took place between 1913 and 1937. Following Vanderlip’s death, there has been little or no management of the birds. They have wandered off the Vanderlip property and reproduced freely. As the flocks have grown, so has their territory. The birds’ range now includes the municipalities of Rancho Palos Verdes, Palos Verdes Estates, Rolling Hills, Rolling Hills Estates, and San Pedro. The birds are responsible for serious property damage to homes, landscaping, and vehicles. During the breeding season, residents must deal with the birds’ nocturnal cries and diurnal aggression. Municipalities had enlisted the assistance of humane society, animal control, and police officers. One community legislated the birds’ territory to be two neighborhoods. All of these efforts had minimal impact on bird number and territory size. Recently, the cities of Rancho Palos Verdes and Palos Verdes Estates requested the assistance of the University of California, Davis. University researchers initially conducted bird counts. Subsequently they assisted in increasing the number and improving the nature and placement of peafowl traps. These efforts resulted in significant numbers of birds being trapped and relocated to appropriate adoptive homes. Removal of any of the birds is opposed by a small group. These citizens engage in activities that are counterproductive to the trapping efforts. Ongoing trapping, citizen education, and a peninsula-wide approach to peafowl management is needed.
Blackbird damage to rice has become a major economic problem for growers in Morelos, Mexico. Blackbirds, specifically the red-winged blackbird (Agelaius phoeniceus), brown-headed cowbird (Molothrus ater), and the red-eyed cowbird (M. aeneus) caused approximately 3.68% damage per hectare during spring-summer 2000. Other species such as the blue grosbeak (Passerina caerulea) and the blue-black grassquit (Volatinia jacarina) damage rice crops too, but mostly in the field borders near secondary vegetation or other crops like sugar cane or maize.
Bird-aircraft collisions (bird strikes) are an increasing safety and economic concern to the USA civil aviation industry, costing over $400 million each year. One approach to reducing risks associated with strikes is to require commercial aircraft components to meet certain standards of safe performance in the event of a bird strike. The Federal Aviation Administration has developed airworthiness standards for airframes, windshields and engines using a single 4-lb (1.82-kg) bird mass as the maximum that must be tested (with the exception of a single 8-lb bird for the empennage, 6-lb bird for certain mid-sized engines that may be developed in the future, and an 8-lb bird for certain large-intake engines on aircraft such as the Boeing 777). Because of concern within the aviation industry that populations of certain flocking bird species weighing more than 4 lbs, such as Canada geese (Branta canadensis), have increased dramatically, discussions are underway in the USA and Europe regarding the need to revise 4- and 8-lb test standards to heavier body masses or to include multiple strikes. To help clarify this issue, we surveyed the avian literature and determined that 36 and 14 of the approximately 650 bird species that nest in North America (north of Mexico) have average body masses (for at least 1 gender) greater than 4 and 8 lbs, respectively. Of the 31 species for which population trend data were available, 24 (77%) showed population increases over the past 20-40 years, 2 showed declines, and the other 5 were stable. Thirteen of the 14 species with mean body masses over 8 lbs showed population increases. At least 261 strikes with >4-lb birds caused substantial damage to civil aircraft in the USA, 1990-2001. Furthermore, multiple birds were involved in 31% of the strikes with >4-lb birds and 40% of the strikes with >8-lb birds. Therefore, we conclude that airframe, windshield, and engine standards, as well as proposals to allow high-speed (>250 knot) operations below 10,000 feet, should be reevaluated to address the threat posed by increased populations of large flocking birds. Finally, because most critical aircraft components are not designed to withstand strikes by birds greater than 4 lbs, wildlife biologists who work at airports should increase efforts to detect, remove and disperse these large birds from airport environments.
As domestic air travel and wildlife populations have increased in recent years, wildlife-aircraft collisions (wildlife strikes) have increased, prompting concerns for human safety and the economic impacts of wildlife strikes. Most of these wildlife strikes occur in the immediate vicinity of airports. Therefore, removal of wildlife attractants from the airfields themselves is an important component of effective wildlife strike hazard management programs. In response to a such a wildlife strike problem, the U.S. Department of Agriculture’s Wildlife Services program initiated a wildlife hazard mitigation program at airports in north-central Kentucky which included direct control of raptors. To identify the food-based attractants that may be attracting raptors to these facilities, we salvaged digestive tracts from carcasses of raptors removed from these airports and identified food items contained within. These data will be used to focus prey-base management activities and help reduce the attractiveness of airfield habitats to foraging raptors in an effort to reduce wildlife strikes and the need for direct control of these birds.
Resolving conflicts between people and canada geese: the need for comprehensive management approaches
Canada geese have become established and are now numerous enough in many urban and suburban areas that conflicts with humans have become frequent. Although potential threats to human health are often cited as a justification to manage goose populations, currently available science suggests that this is not a serious issue. This leaves the primary concern as one of aesthetics– people do not like having to deal with what can sometimes be copious amounts of goose droppings. Animal welfare interests have questioned the humaneness of different roundup and killing programs, and advocated non-lethal approaches and egg addling. Both approaches currently are being practiced in a number of different communities without, unfortunately, much being done to systematically monitor or evaluate them. This paper addresses some of the more controversial issues surrounding resident Canada goose management from an animal welfare perspective and touches on some of the different management approaches currently being practiced as examples of the need for better overall coordination and comparison of management approaches.
The resident Canada goose (Branta canadensis) population in Truckee Meadows (TM) increased in the 1980s from a few hundred to an estimated 1,200 by 1988. Concern arose after two incidents in which aircraft from Reno/Tahoe International Airport hit resident geese. As a result of a FAA mandate, a multi-agency task force led by USDA APHIS Wildlife Services was developed to address the problem. As a result of a recommendation from the task force, an annual Canada goose round-up with subsequent relocation was started in 1989 and has continued through 2001. Of the 7,954 geese initially captured, 3,081 (39%) were recovered (death, recapture, sighting) at a later date at least once. Of the 11,397 captures (newly banded and recaptured geese), 5,269 were released at the capture site and 6,128 were relocated. In addition, 347 geese were captured and released in TM in 1986-87 for a study conducted by the Nevada Division of Wildlife (NDOW). During the first few years of the program, juveniles and some adults captured in TM were relocated. Since 1997, all geese captured have been relocated. Of the geese released at the capture site prior to 2001, 59.6% of the adults and 40.6% of the juveniles were recovered at least once in TM. Comparatively, only 21.2% of the first-time relocated adults and 3.5% of the relocated juveniles have returned to TM, a significant difference for both (P<.0001). Second-time released and relocated adults were recovered a third time in TM at 68.5% and 32.8% (P<.0001). However, adults released or relocated 3 or more times have been recovered similarly in TM at 69.5% and 71.0% (P=.846). Relocated geese are subject to higher hunting mortality by about 8% (P<.0001); hunting as a management tool appears to have helped reduce the returning population. As a result of the relocation program, the population in TM has declined from a high of about 2,000 to 400 at the same 10 sites. The current population throughout TM is about 800. We conclude that the relocation program has been effective in reducing the Canada goose population in TM, except that relocating geese three or more times is not worthwhile.
We evaluated our ability to deliver adequate daily doses of the reproductive inhibitor, nicarbazin, to individually marked resident Canada geese (Branta canadensis). We also evaluated the efficiency of nicarbazin in reducing egg hatchability. The study was conducted prior to and during the egg-laying period at a wildlife sanctuary that has a large, problem-causing population of resident geese that were accustomed to being fed by people. Twenty-eight adult females were marked with individually identifiable neck collars, 24 of which were affixed with radio transmitters. Grit pellets and gelatin capsules containing nicarbazin were fed to these geese from March 17, 2001 through April 26, 2001. We attempted to deliver doses to geese each day. Doses varied among geese throughout the study and within geese daily because all geese were not present at the site each day, and even if present they accepted the bait to varying degrees. Seven of our target birds did receive what we believed to be adequate doses of nicarbazin. We documented that only about 11% of the resident population nested at the sanctuary, while the others nested in remote areas. We were able to locate 5 nests of birds that received adequate doses, but found no significant effect of nicarbazin on the hatchability of their eggs compared to untreated geese. We found that the biggest challenges to orally-fed reproductive inhibitors include the palatability of bait relative to other food sources, reduced feeding during the breeding period, and movements and territoriality associated with nesting.
The continued expansion of coyote activity to new areas, the growth and expansion of human populations, undiminished difficulties faced by livestock producers in managing predation, and highly polarized public values have challenged the abilities of a new generation of scientists and students to develop effective, socially acceptable predation management methods. Work by scientists at the National Wildlife Research Center, their students, and numerous cooperators has resulted in more than 150 research papers, reports, theses, and dissertations during the past decade, substantially increasing the body of knowledge of coyote management strategies and describing progress in the development of new management methods. Much of the effort has focused on research on non-lethal techniques, methods that are selective for individual problem animals, and procedures perceived by the public to be more humane. More than two-thirds of the predator research scientists now at the Center were hired during the past decade, bringing fresh perspectives and new talent to the pervasive problems of livestock predation by coyotes.
Toxicant ejectors have been important in coyote control since the late 1930s when the coyote getter (CG) was introduced into Governmental wildlife damage management programs in the western United States. The CG was replaced during 1968-1970 by the similar but safer, spring-activated M-44 device that remains in use today. Significant aspects of this history include the private development and manufacture of the CG, first called the Humane Fur Getter, in the 1930s; adoption of the CG by governmental and private predator hunters; technical performance problems with CGs (and later M-44s) and their cyanide cartridges and capsules; governmental efforts to resolve these problems; development of competing toxicant ejector models, and evaluations of them compared to the CG; human injuries from CG accidents, leading to development and adoption of the safer M-44 ejector; the 1972 ban on sodium cyanide (NaCN) and other predacides; resumption of NaCN use in M-44s experimentally in 1974, followed by EPA registration in 1975; evaluation of alternate toxicants compared to NaCN; and the many minor but collectively important changes that have resulted in today’s improved M-44. The invention and technical evolution of CG and M-44 devices is described chronologically, with emphasis on the development, manufacture, and use of these devices in Federal/cooperative animal damage control programs.
Depredation management outside the box: logical adaptations of successful practices with other species and situations
Social, legal, biological, and political constraints dictate the need for new and improved methods of depredation management. One under-exploited approach to address these constraints may be the adaptation of methods from other damage management situations. We discuss several of these methods. Two examples are pre-baiting and diversionary feeding. The former is a standard feature of rodent control programs, but seldom if ever implemented with predators. We discuss preliminary evidence that pre-baiting increases the efficiency (and perhaps the selectivity) of some coyote management tools. Similarly, diversionary feeding is an integral component of black bear damage management for industrial timber in the Pacific Northwest. We are currently testing the hypothesis that diversionary feeding also reduces black bear depredation on livestock. Other plausible methods to reduce depredation include laser technologies, and habitat manipulation. Our efforts reflect the emphasis placed by USDA Wildlife Services and the National Wildlife Research Center on developing economically and ecologically sound strategies to manage predation on livestock, big game, and other wildlife species of concern.
Non-lethal radio activated guard for deterring wolf depredation in Idaho: summary and call for research
With the reestablishment of wolves in the western United States, managing adverse interactions between wolves and livestock is re-emerging as an issue for resource managers. Lethal control of wolves is often difficult to implement due to the constraints of the Endangered Species Act, predator population goals, and public disfavor for lethal control. In response to the need to manage wolf predation in a non-lethal manner, we developed and tested a behavior contingent system for disrupting predation events. The Avian Systems Model 9000 Frightening System, also called a Radio Activated Guard (RAG), is activated by signals from nearby wolf radio collars. The strobe light, tape player with 30 different recorded sound effects, and behaviorally contingent activation are designed to minimize habituation to the system. Based on studies in Idaho, we believe RAG boxes are effective for protecting livestock in small pasture situations. Limitations of the scare device include electronic complexity, area coverage, and price. We continue to develop and test the limitations of their effective use in ongoing experimental research.
Electronic training collars have previously been used to condition captive predators not to attack livestock and other prey, but the use of aversive collars in actual management situations involving wild predators has not been scientifically evaluated and published. We adapted and tested commercially available dog training collars in an actual management situation involving wild wolves. Because we temporarily held wolves in captivity, we also discuss the use of pens as a tool that provides management flexibility. Three packs that had been implicated in killing livestock were held at a pen facility at the Flying D Ranch near Bozeman, Montana. Wolves from 2 packs were used in training collar experiments. We ran trials using bison calves, domestic cow calves, and hides to test equipment and the behavioral conditioning paradigm. In our program, we were unable to condition wolves not to attack livestock because of a variety of logistical and behavioral reasons. We concluded that temporarily holding wolves at a small, moderately accessible facility is of limited use for determining the utility of aversive conditioning as a wolf predation management technique. More research is necessary to effectively apply electronic training collars to wolf management. However, we determined that maintaining holding pens for wolves provides flexibility to managers in translocation efforts. Because wolves in our studies survived to reproduce, our collaborative efforts have made a significant contribution to wolf recovery.
Persistence of unique rabies virus variants in a diverse array of terrestrial carnivores and insectivorous bats makes rabies control in the U.S. a complex task. The public health system in the U.S. is effective in keeping human deaths near zero each year in the face of enzootic wildlife rabies, but the annual cost of coexistence with the disease is high, exceeding $300 million. In addition, each year tens of thousands of people are impacted by anxiety, fear, and trauma associated with potential or actual rabies exposure to themselves and their domestic animals. Exclusion, proper storage and disposal of garbage, and removal of problem animals are often effective alternatives to address wildlife rabies threats at specific sites; however, oral rabies vaccination (ORV) is the only currently available technique that shows promise for wildlife rabies control on a broad geographic and species scale. In this paper, we discuss progress toward using ORV to contain specific terrestrial rabies virus variants in the U.S. and planning towards coordinated national efforts to explore the elimination of terrestrial variants of rabies virus in the U.S.
Environmental loading rates of the waterborne pathogenic protozoa Cryptosporidium parvum in certain domestic and wildlife species in California
Waterborne transmission of the pathogenic protozoa Cryptosporidium parvum has emerged as an important public health concern. To develop focused strategies to minimize the risk of waterborne transmission of this parasite to humans or animals, a standardized methodology is needed for comparing environmental loading rates for different populations of vertebrate hosts for C. parvum. A reasonable approximation for an estimate of the environmental loading rate is to measure the prevalence of infection and the intensity of shedding using cross-sectional surveys of the mammalian population, and then multiplying by an estimate of fecal production. We applied this concept to a variety of livestock and wildlife species found throughout California. In general we found that regardless of age, striped skunks, coyotes, California ground squirrels, and yellow-bellied marmots were substantial sources of C. parvum oocysts. In contrast, only the young stock of beef and dairy cattle were substantial sources of oocysts; adult cattle appear to excrete only limited numbers oocysts relative to either calves or wildlife. Watershed management plans that endeavor to minimize contamination of drinking water with C. parvum need to focus on appropriate management of wildlife reservoirs of C. parvum in addition to the traditional concern of animal agriculture.
Lyme disease is an emerging infectious disease accounting for more than 90% of all reported vector-borne diseases in the United States. In the eastern U.S., the deer tick Ixodes scapularis carries the spirochete Borrelia burgdorferi, which causes the disease. The main reservoir for the spirochete in the wild is the white-footed mouse Peromyscus leucopus, which serves as the most common blood-meal host for the larval and nymphal life stages of the tick. Additionally, the enzootic cycle includes the white-tailed deer Odocoileus virginianus. As the human incidence of Lyme disease continues to increase, effective intervention methods are needed. Control methods for decreasing risk of contracting Lyme disease have been developed and center on targeting the tick or the wildlife hosts that harbor the tick vector. Personal protective measures have also been developed to protect individuals potentially exposed.
The pest management strategy for bovine tuberculosis (Tb) in New Zealand aims to achieve official freedom from Tb before 2012 and to eradicate the disease from livestock and wildlife. On farmland, regularly tested cattle and deer usually provide adequate surveillance of Tb presence in sympatric wildlife, but there are many other areas where livestock are absent or their densities too low to be useful. For these areas, Tb prevalence in the wildlife hosts must be surveyed directly but brushtail possums (Trichosurus vulpecula), the main host, make poor sentinels (indicators) for identifying Tb presence or absence. Consequently, persistent Tb can go undetected for long periods. The trials reported here assess the feasibility and practicality of alternative techniques for Tb surveillance in wildlife – the use of ‘spillover’ hosts as sentinels for detecting Tb presence or helping quantify its likely absence. Spillover hosts become infected mainly through interaction with other species. This paper will discuss the use of these species to detect both the presence and the spread of bovine Tb in wildlife in the central North Island of New Zealand.
Professional use of pesticides in wildlife management an overview of professional wildlife damage management
Wildlife damage management is an important, often neglected, part of the wildlife management profession. Wildlife sometimes cause significant damage to agricultural crops and livestock, forests, rangelands, private and public property, other wildlife and their habitats, and urban and rural structures. Wildlife can also threaten human health and safety. Prevention of wildlife damage may involve use of pesticides and drugs. These include anticoagulant toxicants, acute toxicants, fumigants, repellents, frightening agents, aversive conditioning agents, contraceptives, immobilizing agents, and use of herbicides to alter habitat. This discussion will focus on the Wildlife Services program as professional users of pesticides and will examine the types of pesticides used, the reasons for their use, the magnitude of vertebrate pesticide use, and will touch on the degree of hazard inherent to those uses. Risks to wildlife associated with use of vertebrate pesticides are usually less than those associated with use of conventional herbicides and insecticides— amounts used are small, use sites are limited in area, and vertebrate pesticides generally show some specificity in their action. Also, rather than managing vertebrate pests on a population level, the trend in current wildlife management is to deal selectively with problem animals or problem situations on a local basis.
Regulatory changes beginning in 1972 have led to increased emphasis on the safety of pesticides and decreased emphasis on efficacy. Many vertebrate pesticides are undergoing reregistration. Others have lost some or all uses. Toxicants registered to control vertebrate pests tend to have safety issues. Efficacy usually is the greater concern for repellents, although EPA seldom requires substantiation of effectiveness for vertebrate repellents, some of which no longer are required to be registered. Vertebrate pest control devices still are being marketed in the U.S. Truth-in-labeling is a significant issue for vertebrate pesticides and devices.
Phosphine exposure to applicators and bystanders from rodent burrow treatment with aluminum phosphide
An industrial hygiene study was conducted to monitor levels of phosphine gas exposure of applicators and bystander environment during use of aluminum phosphide tablets where used to treat rodent burrows, or when entering treated fields and adjacent buildings. State-of-the-art Draeger Pac III monitoring units and Draeger Phosphine Badges were placed on 33 applicators using Fumitoxin® tablets to treat ground squirrels (Spermophilus spp.) and pocket gophers (Thomomys spp.). Applicators represented both frequent and infrequent users. Agricultural and urban area applicators and bystander conditions in 9 California counties were monitored. Bystander sites were monitored with the Pac III data logging equipment. Thirty concrete slab or raised foundation buildings and 9 outdoor park and almond or walnut production sites were monitored for phosphine gas. No applicator phosphine exposures were above either the permissible 8-hour Time Weighted Average (TWA) of 0.3 ppm (Permissible Exposure Limit - PEL), or the 15-minute Short Term Exposure Limit (STEL) of 1.0 ppm. Higher exposures were observed for non-certified infrequent users than for certified or non-certified frequent applicators. The average TWA for applicators was 0.035 ppm, about 10% of the PEL. Label directions are satisfactory to avoid excessive worker exposure and environmental impact. Several work practices were associated with higher exposure potential, and recommendations were made for their mitigation to further reduce exposure. All exposures to PH3 were related to poor handling procedures that could be avoided by following the label and proper training. Average PH3 levels at potential bystander sites inside and outside residences were well below the 0.3 ppm TWA. No building registered over 10% of the PEL. In the outside trials, there were only 2 Pac III readings of over 100 that indicated detectable 8-hour TWAs at ground squirrel sites. The sites were very heavily infested, and PH3 only slightly exceeded 10% of the PEL. No PH3 was detected above pocket gopher burrows in any field site. When used according to the current label, the potential PH3 exposures of applicators and bystanders are low relative to the Low Observed Adverse Effect Level and are within existing occupational standards. Training was associated with lower worker exposures of certified applicators and non-certified frequent users compared to non-certified infrequent users.
Assessment of hazards to non-native mongooses (Herpestes auropunctatus) and feral cats (Felis catus) from the broadcast application of rodenticide bait in native Hawaiian forests
Primary non-target hazard assessment can be separated into two basic components: bait acceptance and toxicity. This bait acceptance study investigates the potential primary non-target hazard (direct consumption of bait pellets) that the broadcast application of rodenticide bait may pose to non-native feral cats and mongooses. The study was conducted in 4 different forest habitats in Hawaii using 2 different commercial formulations of placebo bait pellets. We documented vertebrates that came to placebo bait pellets at bait monitoring stations to assess bait acceptance. Bait pellets were monitored at each site using 40 infrared (IR) monitors/data loggers and weatherproof automatic cameras. During the 80 days of the study, cameras operated for 76,800 hours and recorded 21,211 slides of vertebrates at bait stations. Rodents, the target species, were the largest group, documented at stations in 98.98% (n = 20,994) of these photographs. Feral cats were detected in 0.09% (n = 20) and mongooses in 0.46% (n = 97) of the slides of vertebrates at bait pellets. The 117 photos of feral cats and mongooses represent 44 occasions where these predators encountered bait pellets; in 14 of these the bait was eaten. These data suggest that the primary hazard to non-native feral cats and mongooses from the broadcast application of pelletized rodenticides is very low. Thus, this study should support the effort to obtain regulatory approval for the broadcast application of rodenticide bait for conservation purposes in the state of Hawaii.
Learned bait-shyness by possums (Trichosurus vulpecula) towards baits containing cyanide, 1080, cholecalciferol, or brodifacoum
Around NZ$76 million per annum is presently spent on controlling and researching the introduced brushtail possum in New Zealand. The national control effort is likely to be further increased over the next decade in an attempt to eradicate bovine tuberculosis and to arrest the degradation of key conservation areas. There is a risk that repeated control operations using toxic baits could result in widespread development of learned “bait-shyness,” behavior that develops when sublethally poisoned animals are able to link the experience of an illness with the memory of the bait eaten. Four studies are reviewed that aimed to determine the likelihood of possums becoming shy after sublethal doses imparted by different types of toxic bait, and to find solutions to the problem. Captive possums were presented with baits containing sublethal doses of the 4 vertebrate pesticides commonly used. Following a recovery period, possums were presented with lethal baits and their response compared with that of naive possums. Between 15% and 90% of possums previously dosed with sublethal doses of cyanide, 1080, or cholecalciferol developed bait-shyness, the proportion being dose and toxicant dependent. Although cholecalciferol induces toxicosis more slowly (i.e., >24 h) than cyanide (5 min) and 1080 (1 h), possums were nevertheless able to associate the effects of this toxicant with consumption of the bait in which it was delivered and avoid eating further baits. However, brodifacoum acts very slowly (1-4 weeks), and possums did not become shy towards baits containing this toxicant after first eating sublethal baits. Shyness induced by either 1080 or cyanide persisted for at least 12 and 24 months respectively, thus jeopardizing the effectiveness of “maintenance” control operations, which can be required every 12 months or less. The persistence of bait-shyness to cholecalciferol remains untested. Use of alternative baits (bait-switching) proved an effective solution for eliminating cyanide- and 1080-induced bait-shyness. Baits containing brodifacoum can also be used very effectively to “mop up” bait-shy populations, but care must be taken to minimize environmental contamination by this persistent compound.
Human poisonings and rodenticides: evaluation of incidents reported to the American Association of Poison Control Centers
Accidental human exposure to pesticide products is a major concern of the U.S. Environmental Protection Agency (EPA). One condition of product reregistration is the submission of product-specific incident report summaries from the American Association of Poison Control Centers (AAPCC) Toxic Exposure Surveillance System (TESS). Between 1986 and 1998, the AAPCC received a total of 22,921,827 incident reports from telephone calls and physician reports. The total number of incident reports per year more than doubled between 1986 and 1998, with 2,241,082 incidents in 1998. While the total number of incidents increased each year, the reporting per year rate remained constant at approximately 9 reports per 1,000 individuals. Rodenticide related incident reports increased from 8,705 in 1986 to 20,300 in 1998. However, the yearly reporting rate for rodenticide incidents remained constant at approximately 8 reports per 100,000 individuals. Since 1990, anticoagulants have consistently accounted for 82% to 89% of all rodenticide exposures and “long-acting” anticoagulants (i.e., 2nd generation compounds such as brodifacoum) have accounted for 83% to 91% of all anticoagulant incidents. Although there was variation between years, there were approximately 150 incident reports each year for both strychnine and zinc phosphide. “Unintentional” exposures accounted for approximately 85% of all incidents reported to the AAPCC. With the exception of strychnine, unintentional exposure to rodenticides was slightly higher, at 90%. In the case of zinc phosphide, nearly all exposures (>97%) were unintentional. The majority of exposures involved children less than 6 years old. However, adults were reported to be involved more than 50% of the strychnine incidents. Despite the high number of exposures, very few cases resulted in more than minor symptoms.
This paper discusses the more common methods of mole control used in the U.S. Field efficacy data are presented with a new product, Kaput® Mole Gel Bait, containing 250 ppm warfarin. Initial field studies in St. Louis, MO with a 500-ppm warfarin bait in 1998 yielded 50% efficacy within 5 days. The following year, a 250-ppm warfarin gel bait yielded 85% efficacy after 7 days of application. Field tests conducted in Ohio resulted in 90% control of eastern moles. Results from a field test in Oregon using warfarin alternate formulation and diphacinone gel baits demonstrated 47% and 80% control of Townsend’s mole within 15 and 7 days respectively.
Two experiments were conducted evaluating the efficacy of a castor oil based mole repellent in 2000 and 2001. Five lawns located in central Kentucky were used in a pilot study conducted from April to August 2000. The following treatments were applied at each lawn: no activity, flattening hills and burrows, flattening hills and burrows with 19.5 kg/ha Molexit™, flattening hills and burrows with 39.0 kg/ha Molexit, 19.5 kg/ha Molexit, and 39.0 kg/ha Molexit. Lawns were monitored for 4 months and increases or decreases in activity were noted. There was no difference (P> 0.05) in burrowing activity between the treatments. All sites showed a decrease in mole activity as evidenced by burrowing activity. Possible explanations include a severe drought and product manufacturing problems. Thirty-eight lawns in central and western Kentucky were used in the second study that was conducted from February through June 2001. The treatment unit for this study was the individual lawn, not plots located within lawns. Twelve lawns were flattened, 15 were treated with 19.5 kg/ha Molexit, and 11 were treated with 39.0 kg/ha Molexit. Untreated sites were located immediately adjacent to the treated areas to determine if the moles would relocate to the untreated areas. There was no difference (P > 0.05) between treatments, however lawns treated with the repellent showed larger decreases in activity. There was a difference (P < 0.0001) in treated compared to untreated lawns. Mole activity decreased an average of 28.0 m in the flattened lawns and activity was noted in 9 of the 12 lawns. Mole activity in lawns treated with 19.5 kg/ha Molexit decreased an average of 34.0 m and no mole activity was recorded for 6 weeks. Mole activity also decreased an average of 32.8 m in lawns treated with 39.0 kg/ha Molexit and no activity was recorded for 6 weeks after application. These results indicate there is some level of efficacy in reducing mole burrowing activity using Molexit.
EXIT™/VARGON™ is a new, reduced risk, non-toxic, environmentally friendly rodenticide developed in Canada. The product will be marketed as EXIT™ in Canada and VARGON™ in the United States. United States, Canadian and international patents have been applied for. The product was given reduced risk status for the control of burrowing rodents in May 1999 and has been accepted for joint review by the PMRA and EPA under the North American Free Trade Agreement. Laboratory and field research trials conducted within both the United States and Canada to determine efficacy for control of ground squirrels (Spermophilus spp.) showed 100% efficacy in the laboratory and 94% to 98% efficacy when used in the field according to label directions. Laboratory trials conducted in Canada to determine efficacy for control of Norway rats (Rattus norvegicus) showed 100% efficacy in the laboratory. Preliminary field trials have been carried out with promising results. EXIT™/VARGON™ is a concentrated mixture of alpha-olefin sulfonate and mustard seed powder (Brassica hirta) in water. Prior to application, the concentrate is diluted 1 part concentrate to 24 parts water to form the field solution. The field solution is applied as a foam to individual burrows through an air-aspirating nozzle. All treated animals become unconscious due to anoxia within 1 minute and death by asphyxiation occurs in less than 3 minutes from the start of application. Application equipment consists of a water tank, 12-volt 3.6-gpm Shur Flow pump, a hose reel, and 100 feet of ½-inch garden hose. The nozzle is a 3-gallon per minute aspirating nozzle with a 12-inch to 16-inch extension tube to create foam. The foam expands 3 to 4 times as it exits the nozzle and fills most burrows in 15 to 20 seconds. Prior to application, burrow entrances are blocked with a wire basket or perforated plastic cones to prevent escape of target animals. Foam is applied through the basket or cone into the burrow. The product can be applied at any time and does not depend on the feeding patterns of the target species for efficacy. Application can be made in early spring prior to emergence, throughout the summer when the animals are active, or in late fall after the rodents begin to hibernate. Burrows must be examined and certified free of threatened or endangered species prior to using EXIT™/VARGON™. The product is very site specific, and selected areas such as playing fields, grazing areas, parks, etc. can be targeted for treatment while wildland areas can be left as habitat for the ground squirrels. Periodic treatments will keep the selected areas free of target species. The product is biodegradable, environmentally friendly, and essentially non-toxic. It is safe to handle and easy to apply. Treated animals die and remain in their burrows. As the product has no systemic toxicity, there is no secondary poisoning risk to humans or other species.
Wildlife-aircraft collisions (wildlife strikes) pose safety risks to aircraft and cost civil aviation over $390 million annually in the USA. We reviewed published studies to summarize findings on habitat management techniques that have shown potential for wildlife strike reduction. Habitat components that may attract wildlife to airports include food, cover, water, and loafing areas. Although maintaining tall herbaceous vegetation on airfields may reduce the attractiveness of loafing and feeding sites for some species of birds such as gulls, this strategy may also increase cover and food resources for other hazardous species. Thus, optimum vegetation height management strategies require further research and may be site-specific. Replacing attractive vegetation with less palatable vegetation has also been recommended, but studies with widespread application are lacking. Removal of ornamental trees and shrubs reduces cover for deer and small mammals and nesting sites for birds while also reducing availability of perches. However, exclusion techniques are also needed for reducing the availability of artificial perches and water. Despite more than 30 years of substantive discussion on the importance of these habitat management techniques, few reliable studies of the effectiveness of these techniques have been conducted under operational airport conditions.
Two species of neotropical frog, Eleutherodactylus coqui and E. planirostris, have been introduced into the state of Hawaii via the horticulture trade. Since 1997 frog colonies within the state have rapidly spread from accidental and intentional causes, and frog abundance within colonies has grown rapidly. Colonies of these frogs are currently known from 262+ locations on the island of Hawaii, 45+ on Maui, 35+ on Oahu, and 2+ on Kauai. Although these frogs were originally restricted to horticulture sites, they are now found in residential areas, resorts and hotels, and public lands. Within their native range, they may reach densities of 20,000 frogs/ha. Given the current population irruptions of these frogs in Hawaii, similar densities are being reached and exceeded. Due to the high potential biomass of introduced frogs there are realistic anthropogenic (economic and quality of life) and ecological concerns associated with their spread. Since 1998, research has been conducted with the goal of developing control techniques for these frogs. A primary result of this research effort was the determination that a spray application of a 2.0% concentration caffeine and water solution can effectively eliminate local frog populations. The aforementioned research result was used to support a United States Environmental Protection Agency Sec. 18 (Emergency) Registration for the use of a 2% caffeine solution for Eleutherodactylus frog control in the State of Hawaii by the Hawaii Department of Agriculture. Although this tool is available for localized control of frogs, efforts by federal, state, and county agencies to control this pest in Hawaii has been hampered by a lack of funding, unclear legal jurisdiction, and bureaucratic inertia.
Iterative (1 variable-changed-at-a-time) Lotus 1-2-3® spreadsheet calculations were used to derive hypothetical benefit:cost ratios (BCRs) based on the recommended-use patterns for a commercial turf repellent (Rejex-It®) to deter Canada geese from grazing/loafing on golf fairways and for a commercial shrub/plant repellent (Deer I Repellent®) to deter deer from browsing on landscape shrubbery. Scenarios were based on “real-world” costs of products and valuations of resources. Plots of the BCR-response surfaces for Rejex-It® on fairways showed that BCRs for these turf applications ranged between 63.9 and 0.73. These BCRs showed transitivity, with highest to lowest BCRs linked with revenues from 90+ foursomes per day, 28-day spray intervals, 3.34 ha of fairways, and a $2.00/ha application cost versus 45+ foursomes/day, 7-day spray intervals, 10.24 ha of fairways, and a $10.00/ha application cost, respectively. A plot of BCRs for using Deer I Repellent® based on replacement outlays for shrubs yielded BCRs between 47.12 and 0.52. This response surface yielded transitivity within shrub-size/-number classes and had enhanced “scallop;” all BCRs for 6 and 12 spray applications involving 10-40 shrubs, 0.305-1.122-m radius plants, and 20-100% damage were ≥2.27 (i.e., more than double the cost outlays for the chemical). Although requiring a number of assumptions, our approach provides useful decision-making aids for persons interested in the economics of wildlife damage management methods. The main advantage is that projections of the combinations of variables associated with the potential “break-even” point (BCRs =1.0) for these interventions are available a priori, and that scenarios can be modified with relative ease to view the benefit-cost impacts of other input variables or model assumptions.
An evaluation of chemical repellents and Vexar bud caps to reduce winter deer and elk browsing on conifer seedlings in northern Idaho
Wintering deer and elk can cause extensive browsing damage to forest plantations. This study was undertaken to identify the cost-effectiveness of two repellents (Plantskydd and Deer-Away BGR Liquid) and Vexar bud caps in reducing browse damage to conifer seedlings. Three plantations located on traditional winter range were selected for the study. The 3 sites were rated by pellet group counts as either elk range, deer range, or both elk and deer range. Treatments were applied to each site in the fall of 2000 in a randomized block design. Trees were then surveyed for damage 5-6 months later once snowmelt had occurred and the animals had migrated to higher elevations. All 3 treatments were equally effective in reducing terminal browse damage by up to 42% when compared to controls on the elk range and deer range sites. However, the site with equal deer and elk use received low browse pressure and no treatment differences for terminal damage were detected. The results of this study should be interpreted with caution, as the winter of 2000-01 was relatively mild in northern Idaho, resulting in a snowpack of 50% of normal. Thus, browse pressure may also have been less than normal. Nevertheless, the 3 treatments tested appear to be effective in reducing both deer and elk winter browsing of conifer seedlings at low to moderate levels of browsing pressure.
Black bears (Ursus americanus) strip bark from coniferous trees to feed on newly forming vascular tissue during spring. Damage inflicted through this behavior can be extremely detrimental to the health and economic value of timber stands. A supplemental feeding program to provide bears an alternative food source during spring is practiced by some resource managers. We evaluated the efficacy of the program and conducted concurrent studies to assess select behavioral characteristics of feeding bears and impacts of providing supplemental feed on nutritional status of bears. The efficacy study revealed the percentage of damaged trees in stands with foraging bears varied from 2% to 52%. When supplemental feeding was introduced on these stands, damage was reduced to approximately 10% of that sustained on untreated stands. Concurrent experiments provided insightful data on bear use of feeding stations. Numerous bears fed at the stations, including females with and without cubs, yearlings, and boars. Bear feeding bouts at the stations were generally short, less than 30 minutes. Bears generally fed alone, although 2 to 3 adult bears were observed at a feeder simultaneously and the feeding partners were not consistent. There was little antagonistic behavior observed around the feeders, and no evidence that this behavior inhibited foraging opportunities for long. On the rare occasion a bear was driven from a feeder it returned later that same day to feed, generally within an hour. Supplemental feeding also did not affect the home range sizes of bears in feeding areas, but it may serve to concentrate bears in a particular location. Bears consuming supplemental feed did gain a significant nutritional advantage while feeding, but this did not equate to long term increases in age-specific body masses or fat content.
Benefit-cost analysis (BCA) involves comparing all of the gains and losses from a given wildlife damage management action or management technique over time in similar units, thereby providing a total picture of potential gains and losses to society. This technique is at the core of justifications for wildlife damage management efforts. BCA has been noticeably absent from the study of vertebrate pest management problems, and in the few studies where a BCA has been included, the analysis is incomplete. This paper provides an overview of the steps in a BCA, using specific wildlife damage examples to highlight and expand the technique for researchers interested in documenting these effects.
The Internet Center for Wildlife Damage Management (ICWDM) http://wildlifedamage.unl.edu is a web site established as a clearinghouse for businesses, academies, agencies, and other organizations involved in wildlife damage management. The ICWDM features the publication Prevention and Control of Wildlife Damage, and animal information pages with images and text that describe signs of damage and control techniques. The web site also links to wildlife damage control publications at over 40 universities and agencies. It is home to a database containing more than 900 full-text articles from wildlife damage control workshop proceedings. A recent feature is a free directory of wildlife damage control businesses. Current use of the site is at 1,100 hits per day by 90 visitors. Visitors from more than 50 countries use the ICWDM each month. The web site is funded by the USDA-Integrated Pest Management Program and the University of Nebraska.
Management of wildlife-human conflicts in Israel: a wide variety of vertebrate pest problems in a difficult and compact environment
Although Israel is a small country, it sits at the junction of three continents, and has an especially rich diversity of ecotones and wildlife. In addition, Israel serves as a narrow land-bridge on the major migratory route for millions of birds between Eurasia and Africa. Competing with all this wildlife for living space is a relatively dense human population. Israel is quite conservation-minded with strict wildlife protection laws and very little hunting. All these factors contribute to a situation in which there is much human influence over whatever available habitat is left for wildlife. Consequently, wildlife-human conflicts are common and diverse, but are dealt with mainly with non-lethal methods. Millions of migratory birds cross through Israel and share Israel’s small airspace with the Israeli Air Force (IAF). Israel is especially active in Bird Aircraft Strike Hazard (BASH) issues, which are controlled by a variety of means, including real-time radar information of migratory birds, habitat management, and use of border collies at airfields. Wildlife in Israel are vectors for human diseases (e.g., leishmaniasis, rabies, and West Nile fever). To prevent rabies epidemics, Israel has recently begun successful use of oral rabies vaccination (ORV) for jackals (Canis aureus) and foxes (Vulpes vulpes).
The impact of mammal pest animals, including the rabbit, fox, wild dog, feral pig, and feral goat, is one of the most significant threats to biodiversity, community values, and the economy in Victoria, Australia. The management of these pests is a complex issue involving all land types and land tenures. Both the Victorian Government and the community have expectations relating to the management of these pests; sometimes these expectations differ and finding solutions is difficult. To overcome this, the Victorian Government, through the Department of Natural Resources and Environment (NRE), has provided constructive debate on animal welfare issues and developed the Victorian Pest Management Framework (VPMF) to provide a consistent, strategic, and partnership-based approach to pest management, including mammal pests, on both private and public lands and waters. A key principle of the VPMF is that pest management is the responsibility of each land and water manager. Government only becomes involved where the action results in public benefit, incorporates shared investment principles, meets “duty of care” responsibilities, involves all stakeholders, and is consistent with State or Regional Catchment Strategies or Regional Action Plans. Government involvement also includes an accepted responsibility by public land managers to address damage caused to the community by pests that originate on public land and disperse onto adjacent private land. This responsibility is met through the Government’s “Good Neighbour Program.” The clear definition of expectations of community and Government detailed in the document has provided an agreed basis for all land and water managers to work together to develop and implement long-term, effective, safe and integrated management processes that protect and improve Victoria’s biodiversity and natural values and protect its productivity base.
European rabbits (Oryctolagus cuniculis) have been a problem since their introduction to Victoria, Australia in 1834. In North Central Victoria, a regional rabbit action plan was developed to harness and coordinate community action to achieve long-term benefits. This plan focuses the efforts of the community and the resources of government to achieve community and government objectives. Extensive consultation and involvement of all interested stakeholders resulted in joint ownership and commitment to implementation of the action plan. The success of this plan is due to community ownership of the problem and the committed coordinated efforts of all stakeholders. Land managers have the responsibility to implement the control works on the ground, and the Victorian government provides support to encourage landholders to work together by providing technical assistance and some funding to offset the high cost of ripping warrens. At the ground level, community groups develop local action plans (under the Regional Action Plan framework) for their area. Groups demand 80% involvement of all landholders prior to commencing control programs. On-ground works are coordinated from property to property; there are no gaps in control activity. Where landholders do not undertake control efforts that meet the community standard they are recommended to government for enforcement action, which may result in prosecution. The community ownership of the rabbit problem has resulted in an attitude change that believes “rabbit free” is essential and achievable.
The search for a toxicant in native Gastrolobium seed historically reported to make Australian native fauna toxic to the introduced cat and dog
The decline and extinction of Australian mammals since the arrival of Europeans has been catastrophic. Attempts to reintroduce threatened species of native mammals to their former ranges have failed due to predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis silvestris catus). Baiting with poisoned meat baits will control foxes, but feral cats are generally unwilling to consume a bait. This has seen recent reintroduction attempts fail due to cat predation, possibly involving only a few individual animals. Historical anecdotes from Western Australia record the death of cats and dogs after feeding on a number of the native animal species, with the bronzewing pigeons, Phaps chalcoptera and P. elegans, most frequently mentioned. The toxicity of the pigeons has been attributed to the birds’ feeding on seeds from plants of the Gastrolobium genus. Such a mechanism has been suggested to have aided the survival of 35- to 5,500-g mammals in southwest Western Australia when such species have disappeared elsewhere. Analysis of the seeds of members of the genus Gastrolobium has found extremely high levels of organically bound fluorine. Previous studies report this fluorine to be stored in the seeds as monofluoroacetate (MFA – synonymous with Compound 1080). However, a number of the poisoning anecdotes suggest toxicity of the pigeon skeleton, and report times to death which appear too rapid for the known action of MFA or “1080.” The objective of this research is to examine the authenticity of the historical anecdotes and the feasibility of using a skeletally retained natural plant toxicant to aid the reintroduction of native fauna. Those individual cats and foxes effecting the predation may be removed at the first predatory event if the reintroduced fauna were toxic to the predating animal. This is anticipated to greatly improve the success rate of future reintroduction programs. Exhaustive extraction of Gastrolobium seeds with a variety of solvents and subsequent analysis utilizing a fluoride ion-specific electrode, 19F nuclear magnetic resonance, and other techniques has established the presence of a number of fluorinated and alkaloid compounds. Determination of the identity and toxicity of these compounds is expected to identify a compound(s) which may explain many of the historical poisoning anecdotes and could also provide a method for the control of feral cats in native mammal reintroduction programs.
For centuries, trappers, inventors, naturalists, and biologists have searched for animal traps that met a variety of criteria, such as efficiency and durability. And, for at least the last century, individuals and organizations have fostered a movement that declares traps as inhumane, adding another criterion to the search. Trapping animals for fur, particularly for European markets, played an important role in the history, exploration, and settlement of North America, depressing the populations of some furbearer species almost past the point of recovery. Recovery of animal populations depressed through trapping, market hunting, and habitat loss became one of the first major partnership efforts among U.S. states and federal agencies in the developing science of wildlife management. Regulated trapping continues to be an important means for managing abundant furbearer populations, although the vagaries of fur markets and restrictive legislation in a number of states have made this an increasingly difficult task. For more than 50 years, scientists at the USDA Wildlife Services National Wildlife Research Center and its predecessors have engaged in cooperative research to improve animal traps and trapping systems. In the past decade, a series of actions culminated in the establishment of a national program to evaluate traps according to several criteria, including international standards for animal welfare, in order to develop guidelines for best management practices for trapping furbearers. This paper will briefly review the history of U.S. federal trap research and the status of the cooperative trap testing program.
The recent and rapid growth of the private “nuisance” wildlife control industry follows the unparalleled current period of urban and suburban expansion. Nuisance wildlife control businesses range from simple home-based services to sophisticated franchised businesses. The nuisance wildlife control operator may hold an advanced degree in the wildlife sciences, or simply be an entrepreneur without formal education or even background experience in wildlife. State and federal agencies may participate directly or indirectly in nuisance wildlife control, in activities ranging from dissemination of advice or information to actual participation in programs that may lead to removal of animals. Naturally, all of the activities associated with nuisance wildlife control concern the many individuals and organizations in North America that are interested in animal welfare and protection. This paper addresses some of their concerns. We present a survey, summary, and critical analysis of the nuisance wildlife control industry with a special emphasis on what we view as its most problematic and troubling aspects. We discuss model standards, based primarily on existing best practices, and speculate about the future of this activity.