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 25, 2012
This paper reviews the Vertebrate Pest Conference’s beginnings, why it started, and assesses its success in meeting the goals articulated during the opening Conference in 1962. Probably moreso than any other state, California has a diversity of agriculture that gives every vertebrate a chance to become a pest, even those that didn’t originally live in the state. This, and the hard work of Conference founders, made California a logical place to develop a first-rate Conference on all aspects of vertebrate pests. At the first Conference, over 80% of attendees were from California. At the 24th Conference, this had changed with over 40% attendees from other states and almost 10% from other countries. During the first Conferences, the presentations were mostly about current control methods for various vertebrate pests. Now, the topics have shifted to deal more with specific aspects of control such as non-target impacts, pesticide metabolism, etc. The Conference Proceedings have evolved from a collection of 25 “how-to” papers in the first Proceeding to over 75 peer-edited papers in the 24th. Many of these papers, especially in the more recent Conference Proceedings, are cited throughout the international vertebrate pest control literature. Another trend has been the publication of multiple-authored papers. This represents the important goal of the Conference of getting people together to discuss and work on understanding all aspects of vertebrate pest control. It is clear, just by looking around at the audience and reviewing the program for the 25th Conference, that the VPC is doing exactly what the founders envisioned, and in my opinion, it is an unconditional success!
Eastern fox squirrels have been introduced to many regions within the western United States including areas within California, Idaho, Montana, Oregon, and Washington. In California, fox squirrels have been introduced to San Francisco, Fresno, Los Angeles, San Diego, Berkeley, Mount Diablo in Clayton, Bakersfield, and Santa Barbara. The geographic range of the eastern fox squirrel has expanded greatly both through natural dispersal and additional intentional introductions by humans. The fox squirrel has replaced the native western gray squirrel in certain habitats while the two species coexist in other habitats. Western gray squirrels exist by themselves in a third type of habitat even though eastern fox squirrels have occupied adjacent habitat for about 30 years. Habitat Suitability Models (HSMs) have been used to predict the presence and/or abundance of a particular species within a habitat. Analysis of 9 habitat variables using Discriminant Analysis produced a HSM where replacement, coexistence, and exclusion habitats can be identified using only 3 of the 9 habitat variables: average height of ground cover, percent canopy cover, and percent of total trees that are deciduous. A field study underway for over two years at Rancho Santa Ana Botanic Garden in Claremont, CA is testing the validity of the HSM with the study site predicted to be a long-term coexistence habitat. The ratio of western gray squirrels to eastern fox squirrels has gone from 3:1 shortly after the fox squirrel entered the habitat to 1:1, but after 2.5 years of coexistence both species are commonly observed in the study site. The HSM is also being tested through the analysis of additional habitats. Although coexistence of the two species is possible for many decades, the number of western gray squirrels in coexistence habitats is often small, coexistence habitats are geographically isolated from each other, and the probability of extinction of western gray squirrels from these habitats could be high. We are also looking for new habitats which could support western gray squirrels if individuals were moved to these habitats.
The wild pig is an invasive exotic introduced into what is now Florida in 1539 by the explorer Hernanado de Soto. Texas has been home to wild pigs since 1565 with a current population estimate of 2.6 million animals. From 1980 to 1990, a perfect storm of clandestine releases, access to vast amounts of wildlife supplement, and the highest reproductive rate of any ungulate found worldwide led to a wild pig population explosion in Texas. As the range and population of this intelligent omnivore increased over the ensuing 25 years, agronomic damage alone increased to over $50 million annually. Inter-specific competition with and/or predation upon native wildlife species, damage to wetlands and sensitive plant communities, and water quality degradation have also been attributed to wild pigs in Texas. Damage to urban and suburban landscapes has also increased sharply over the past decade and negatively impacted humans via pig-vehicle collisions, greenscape damage to lawns, sports fields, golf courses, parks, and cemeteries. Legal control methods include shooting, snaring, dogging, and trapping. Among these methods, trapping is often cited as the first line of defense for private landowners. However, many landowners fail to employ “best management practices” when attempting to abate damage through population reduction. Trapping wild pigs is a process, not an event. The process includes the following steps: 1) pigs must be trained to bait, 2) sounder size must be estimated via the use of remote-sensing cameras to determine the size of trap needed, 3) pigs must accept the trap presence, and 4) pigs must be trained to routinely enter and feed inside the trap. Following this trapping protocol can save landowners tremendous amount of time and money in the war on wild pigs.
Improving vertebrate pest control operations relies on increasing pest animal interactions with control devices (e.g., bait stations, bait bags, and/or traps). Interactions are encouraged using a variety of baits and lures that stimulate an animal’s visual, olfactory, or auditory sense, orientating the target species towards a control device. On a generalised spatial scale of conspicuousness, an auditory lure will function over a greater distance for mammals in forested ecosystems than both visual and olfactory lures, suggesting auditory lures could have the greatest luring potential. In New Zealand, there is an overabundance of the introduced Australian brushtail possum that is the subject of ongoing control. Ground-based control operations typically use visual (e.g., a flour blaze), and to a lesser extent olfactory (e.g., cinnamon) lures for attracting possums to control devices. However, the potential for an auditory stimulus remains largely unexamined and underutilised. Research presented here expands on previous studies with captive animals and examines the development and field testing of an audio lure for possum control. The results from three preliminary field trials show that possums found audio-lured devices sooner than un-lured devices, and that a greater proportion of lured devices were located over time. In addition, possums were recorded investigating lured sites at a higher rate compared to un-lured sites, suggesting that possums were more likely to interact with a control device if it has an audio-lure than if it does not.
Rangitoto and Motutapu – A Starting Point for Future Vertebrate Pest Eradications on Inhabited Islands
Conservation efforts in New Zealand have removed invasive mammals from more than 130 offshore and inshore islands. Of these islands, just 8 were permanently inhabited by someone other than a government employee. In contrast, many future eradication projects within New Zealand will be undertaken on islands with a resident human population. A recent project that removed 8 mammalian pests from Rangitoto and Motutapu islands (3,842 ha), two intensively visited islands with a small number of permanent inhabitants, provides a potential blueprint for developing invasive vertebrate eradication projects on inhabited islands. A number of lessons can be drawn from the Rangitoto and Motutapu project. A proactive consultation process resulted in strong support for the project, and a transparent approach to communications gained exposure for conservation issues. Efforts to engage the media and maintain transparency were beneficial in responding to public concerns about at the project. The project also demonstrated that the human health and safety concerns associated with trapping, shooting, and the use of toxins could be effectively addressed.
Successful eradications of harmful invasive species have been mostly confined to islands while control programs in mainland areas remain small, uncoordinated, and vulnerable to recolonisation. To allow the recovery of threatened native species, innovative management strategies are required to remove invasives from large areas. We took an adaptive approach to achieve largescale eradication of invasive American mink in North East Scotland. The project was centered on the Cairngorms National Park (Scotland), with the primary aim of protecting endangered water vole populations. The project was initiated by scientists and supported and implemented through a partnership comprising a government agency, national park authority, and local fisheries boards. Capitalising on the convergent interests of a diverse range of local stakeholders, we created a coordinated coalition of trained volunteers to detect and trap mink. Starting in montane headwaters, we systematically moved down river catchments, deploying mink rafts, an effective detection and trapping platform. Volunteers took increasing responsibility for raft monitoring and mink trapping as the project progressed. Within 3 years, the project removed 376 mink from 10,570 km2 (4,081 mi2) with the involvement of 186 volunteers. Capture rate within sub-catchments increased with greater connectivity to mink in other sub-catchments and with proximity to the coast, where there is more productive habitat. The main factor underpinning the success of this project was functional volunteer participation. The project is a reason for optimism that the tide of invasion can be rolled back on a large scale where the convergent interest of local communities can be harnessed. A successor to this project using the same volunteer-based approach and partnership between conservation practitioners and academic scientists is now expanding to up to 20,000 km2 (7,722 mi2). The research of the expanded project component now focuses on depensatory processes operating in very-low-density populations.
Invasive vertebrate species have had devastating impacts on the flora, fauna and landforms of Macquarie Island over a period of 200 years. Following the successful eradication of weka by 1989 and feral cats by 2001, planning for the eradication of ship rats, house mice, and European rabbits began in 2004. Funding of AUD$24.7M was secured in 2007 for a multi-year project based on aerial baiting targeting rabbits and rodents followed by ground hunting targeting surviving rabbits. The first aerial baiting attempt in 2010 was abandoned due to unfavourable weather and shipping delays. The degree of non-target seabird species mortality from limited baiting in 2010 led to a renewed examination of non-target mitigation options. Rabbit Haemorrhagic Disease Virus (RHDV) was introduced in February 2011 to reduce the pre-baiting rabbit population and thus minimise non-target mortality amongst scavenging seabirds. Aerial baiting resumed in May 2011 using 4 AS350 helicopters and a team of 27 people, and was completed by July 2011. No rodents have been detected post-baiting, and the estimated rabbit population of 150,000 has been reduced to fewer than 30 at the conclusion of baiting. The rabbit hunting phase commenced in July 2011 using a team of 15 hunters and 12 dogs and is ongoing, with 3 rabbits accounted for. Hunting and monitoring is expected to take a total of 5 years post-baiting and will be based on annual progress reviews. A minimum of 2 years monitoring will be conducted. Rodent detection dogs will deploy in 2013 to assist in determining rodent eradication success. Six months after baiting, vegetation recovery was already evident, and increased burrownesting seabird activity has also been observed in the first breeding season post-baiting.
Mitigation of non-target species impacts is a key challenge of the Macquarie Island Pest Eradication Project (MIPEP). The project aims to eradicate rodents and European rabbits from sub-Antarctic Macquarie Island through the aerial application of cereal-based brodifacoum bait, followed by a hunting program targeting surviving rabbits. Aerial baiting was attempted in winter 2010 but postponed due to sustained adverse weather that suspended helicopter operations. Following limited baiting in 2010 (10% of the island), non-target mortality of 960 individuals across 6 (of 27) seabird and duck species was recorded. In response, the Australian and Tasmanian governments conducted a review of the project. The review established that some species would be adversely affected by the project in the short-term, but that the island’s ecosystem and most other island species would substantially benefit from pest eradication, confirming the assessments in the Environmental Impact Statement prepared prior to the operation. Enhanced mitigation measures were recommended to minimise non-target species impacts. Of several potential mitigation measures assessed, two principal measures were adopted: releasing Rabbit Haemorrhagic Disease Virus to reduce the rabbit population prior to baiting, thus minimising the number of rabbit carcasses containing poison residues available for consumption by scavengers; and increasing the effort of field teams during and after baiting to remove carcasses (the primary 2010 strategy), in an attempt to minimise the exposure of scavengers to toxic residues. Baiting resumed in May 2011 and two island-wide drops were completed by July 2011. Seabird mortality was monitored, with over 1,460 dead birds of the same species found that were affected in 2010, primarily scavenging seabirds such as kelp gulls, giant petrels, and skua. No species was considered to have sustained impacts that threatened the viability of the local population. King penguin colonies were closely monitored during helicopter over-flights and only minor and transitory impacts were observed. Wandering albatross nests were cleared of bait and chicks were not affected. No marine mammal impacts were recorded. If successful, the MIPEP will be the largest and most complex sub-Antarctic island rabbit and rodent eradication yet undertaken.
Palmyra Atoll National Wildlife Refuge is a moist Central Pacific atoll that supports one of the best remaining tropical forest ecosystems in the region, including 10 species of breeding seabirds and a robust population of the world’s largest terrestrial invertebrate, the coconut crab. Despite these riches, the atoll’s ecosystem has been modified by introduced black rats that were inadvertently brought to Palmyra during WWII. Between June 1 and 30, 2011, a partnership between the U.S. Fish and Wildlife Service, The Nature Conservancy, and Island Conservation successfully implemented a project to remove rats from Palmyra. Independent monitoring of bait application and its environmental effects was undertaken by the USDA. Over the 28-day operation, a team of 41 people from 5 countries utilized 2 helicopters, 10 slingshots, 148 bait stations, and hand spreading to strategically apply 38,561 kg of rodent bait containing the anticoagulant brodifacoum (25 ppm) to Palmyra’s 235 hectares of emergent land. Palmyra’s challenging eradication environment demanded the development of a novel approach, such as broadcast application rates between 75 and 85 kg/ha and the use of “bolas” to bait coastal forest canopy to minimize bait drift into the marine environment. Initial findings show minimal non-target impacts as a result of the project, and post-eradication monitoring has failed to detect rats. Increased recruitment by at least 2 native tree species has been observed. By removing rats from Palmyra, the partnership aims to safeguard the atoll’s indigenous flora and fauna, encourage the reestablishment of extirpated seabird species, and create an ecological refuge for species within the Central Pacific region that are at risk of extinction. This project is a conservation milestone for the Refuge, and it has established a benchmark for eradication campaigns on other tropical islands.
Much of the research on feral cats in Australia has occurred in the continent’s arid and semi-arid regions. Consequently, little is known about the ecology of feral cats in tall forests. Using a combination of both VHF and ‘store on board’ GPS collars, feral cats were tracked in the forests of Far East Gippsland, Victoria, to investigate both home range size and movement patterns. The use of GPS collars to obtain accurate and high volumes of location data allowed the intra-home range movements of feral cats to be examined in ways not previously possible using conventional VHF radio telemetry. Male cats had significantly larger home ranges (MCP 100, mean ± se: 455 ± 126 ha) than females (105 ± 28 ha). Male home ranges overlapped those of females and female ranges overlapped with neighbouring females. Overlaps in female home ranges, in particular of the core areas, indicate that female cats in Far East Gippsland are tolerant of other females and do not actively exclude them. Feral cats in these productive tall forests have smaller home ranges than those in arid and semi-arid regions where food resources are sparse or limited, but larger ranges than those inhabiting farmland and grassland habitats where food resources are generally more abundant. Location data gathered at three different temporal intervals – 6 hourly, hourly, and every 15 minutes, showed that feral cats utilise a Lévy walk-style searching pattern as they move through their home range. Employing a Lévy walk increases the likelihood of encountering prey items that are distributed sparsely in the environment, in turn maximising the potential hunting return for effort expended. These findings will allow managers to adopt a more targeted approach when undertaking feral cat management programs in these habitats by providing information on where to deploy traps, baits or other control measures.
Getting Ready for the Next Step: The Eradication of Feral Cats on Large and Highest Priority Mexican Islands
Mexican islands’ biodiversity is very rich and diverse; several reptile, bird, and mammal endemic species live on them. However, ecological and evolutionary processes have been negatively affected by invasive species. To date, more than 20 island endemics, including mammals, birds and reptiles, have gone extinct on Mexican islands. As a very opportunistic predator that adapts easily to different environments, the feral cat is one of the most lethal invasive species. Restoration of island ecosystems can be achieved effectively by the eradication of this noxious species. In Mexico, 18 islands (<400 km2) have been cleared of feral cats using traditional techniques, i.e. trapping and hunting. These techniques are still being implemented on smaller islands or on islands where populations are small. Nevertheless, on big islands with complex terrain and topography, varied habitats and climates, and with non-target species, there are challenges to overcome. This includes Socorro (130 km2), Cerralvo (135 km2), and Guadalupe (240 km2) Islands. To achieve successful cat eradications on these islands, dispersion of toxic baits will be necessary. Currently, bait trials are being developed by Grupo de Ecología y Conservación de Islas, A.C., and supported by Australian and New Zealand institutions, as part of island-specific eradication plans. To date, these studies comprise feral cat and native species ecology for Cerralvo and Socorro Islands. All data gathered is valuable for eradication planning.
The Influence of Perceptions, Attitudes, and Experiences on the Perceived Risks and Benefits of Free-Roaming Cats
Individual perceptions of free-roaming cats can vary from “voracious predators of small birds and mammals” to “cherished and beloved companion animals.” This paper focused on the influence of situational variables (e.g., experiences with outdoor cats), cognitive variables (e.g., attitudes toward cats and cat management), and demographic variables (e.g., gender, cat ownership) on perceptions of the risks posed by free-roaming cats to the ecosystem and the benefits that cats provide to people. In addition, we analyzed the potential role that risk and benefit perceptions play in mediating the relationship between attitudes toward outdoor cats and tolerance for the future cat population. We conducted an 11-item written survey of 474 undergraduate students enrolled in two introductory ecology courses. There were significant differences in perceived risks and benefits of cats between cat owners and nonowners and cat feeders (people who fed free-roaming cats) and non-feeders. Perceptions of the current cat population, experiences with cats and attitudes toward cats predicted both perceptions of risks to the ecosystem and benefits to people. The relationship between attitudes and tolerance was mediated by individual perceptions of benefits to people from free-roaming cats. Experience with free-roaming cats, attitudes toward cats, affection for cats, and demographic variables predicted individual risk perceptions. These perceptions, in turn, influenced support for future cat population levels and should therefore be addressed in management campaigns aimed at reducing the outdoor population of free-roaming cats.
Domestic cats have been introduced to many of the world’s islands where they have been particularly devastating to insular wildlife which, in most cases, evolved in the absence of terrestrial predatory mammals and feline diseases. We review the effects of predation, feline diseases, and the life history characteristics of feral cats and their prey that have contributed to the extirpation and extinction of many insular vertebrate species. The protozoan Toxoplasma gondii is a persistent landbased zoonotic pathogen hosted by cats that is known to cause mortality in several insular bird species. It also enters marine environments in cat feces, where it can cause the mortality of marine mammals. Feral cats remain widespread on islands throughout the world, and are frequently subsidized in colonies which caretakers often assert have little negative effect on native wildlife. However, population genetics, home range, and movement studies all suggest that there are no locations on smaller islands where these cats cannot penetrate within two generations. While the details of past vertebrate extinctions were rarely documented during contemporary time, a strong line of evidence is emerging that the removal of feral cats from islands can rapidly facilitate the recolonization of extirpated species, particularly seabirds. Islands offer unique, mostly self-contained ecosystems in which to conduct controlled studies of the effects of feral cats on wildlife, having implications for continental systems. The response of terrestrial wildlife such as passerine birds, small mammals, and herptiles still needs more thorough long-term monitoring and documentation after the removal of feral cats.
Feral cats are abundant in the Hawaiian Islands and pose a threat to native wildlife through predation and the spread of disease. A combination of factors including the submission of state bills and county resolutions has created the impression that a large segment of society supports the presence of feral cats in the islands and in-situ management techniques. The purpose of this research was to quantify the perceptions and desires of Hawai´i residents regarding the abundance and impact of feral cats. In 2011, I disseminated a social survey to approximately 5,000 Hawai´i residents including pre-identified wildlife stakeholders and a random sample of the general public. Data were analyzed using the potential for conflict index (PCI) and Wildlife Stakeholder Acceptance Capacity models. PCI results indicate that there is a high level of consensus within every stakeholder group that the abundance of feral cats should be decreased. Despite this result, 12% of respondents would like to see populations of feral cats persist in the islands. People’s desire to see the abundance of cats reduced was highly correlated (0.54) with whether or not people enjoyed seeing feral cats: 84% of survey respondents dislike seeing feral cats. We also asked survey recipients if feral cats should be removed permanently or relocated away from areas with threatened or endangered wildlife: the majority of people (78%) support the idea of permanently removing feral cats, whereas 10.1% would prefer to see feral cats relocated away from the specified area, and a small proportion of people (3%) believe that feral cats that are being fed do not kill other animals. This research reveals that a small segment of society supports the presence of feral cats, and that the majority of people would prefer to see feral cats removed from areas with threatened native fauna.
Although trap-neuter-return (TNR) programs for feral cats are in use or being proposed in many communities, a number of non-governmental organizations have gone on record as being opposed to them. For example, The Wildlife Society’s (TWS) policy statement on feral cats (2011) includes a comment that TWS “Oppose the passage of any local or state ordinances that legalize the maintenance of “managed” (trap/neuter/release) free-ranging cat colonies.” Similarly, the American Bird Conservancy’s (ABC) resolution on free-roaming cats (feral and tamed) states that ABC “strongly opposes managed free-roaming cat colonies.” Wildlife managers often lament the loss of tools and techniques (e.g., traps, pesticides, regulatory authority) for managing “nuisance” animals. The attack against TNR programs is indicative of an active program to eliminate a management tool. Is the negativity toward TNR justified? Stated another way, do the negative aspects of TNR programs outweigh any positive elements? I argue that the complete rejection of TNR is premature, erroneous, and without merit.
First raised as a serious conservation issue more than 100 years ago, the impact of free-roaming cats on wildlife has been a subject of debate, controversy, and conflict since then. Cats have been tied directly to the extinction of sensitive species in island environments and implicated as major threats to certain wildlife populations elsewhere. Yet the study of free-roaming cats and the problems attributed to them lags behind the standards of research typical with more traditional vertebrate “pest” species. Alternative management approaches, ranging from traditional practices such as removal and depopulation to emerging concepts such as Trap-Neuter-Return (TNR), have yet to be subject to the scrutiny and experimental study that could lay controversial interpretations of their efficacy to rest. Here, we discuss the need for collaborative management concepts and programs to address growing concerns about cats outdoors.
Outbreaks of foodborne illness associated with the consumption of leafy green produce from California and across the United States have heightened the need to identify vertebrate sources of these microbial hazards. Concern has focused on wildlife species that have direct access to the produce production environment and irrigation water supplies. Recent fecal surveys of California wildlife, feral animals, and livestock and companion animals are allowing regulators to compare the food safety risks of such pathogens as E. coli O157:H7 and Salmonella from these various animal species. In order to make valid food safety risk comparisons between wildlife, livestock, and companion animals, a variety of methodological and epidemiological issues need to be addressed in order to avoid substantial biases. For example, the amount of feces tested per animal can vary up to a 1000-fold, substantially biasing the probability of testing positive for large fecal contributors (e.g., cattle) compared to smaller wildlife (e.g., deer mice). Many wildlife species intrude and forage as a group in fields of produce, which can lead to in-field defecation, substantially, elevating the risk of microbial contamination compared to many larger animal species that do not have direct access to produce fields due to fencing. This paper highlights the technical challenges of making valid quantitative comparisons of microbial food safety risks from wildlife compared to other domestic animals.
Detection and Prevalence of Cryptosporidium spp. and Giardia spp. from Wild Rodents Adjacent to Produce Production Fields in California
Between 2009 and 2011, fecal samples were collected from ten species of wild rodents in locations adjacent to leafy green blocks in a major produce production region of California. Samples were screened for Cryptosporidium spp. oocysts and Giardia spp. cysts using immunofluorescent microscopy. Five and seven species of wild rodents carried Cryptosporidium spp. and Giardia spp., respectively. In general, 26.0% and 24.2% of the trapped wild rodents were positive for Cryptosporidium spp. and Giardia spp., respectively. Deer mice (Peromyscus manicultus) were the primary trapped species, with 30.3% (63/208) positive for Cryptosporidium spp. and 25.5% (53/208) positive for Giardia spp.
In 2006, spinach contaminated with Escherichia coli resulted in the death of 3 people and over 200 illnesses. The contaminated spinach was traced to a field in central California. In 2007, produce industry representatives developed safety guidelines (known as the Metrics) for lettuce and other leafy green crops. The Metrics addressed encroachment and crop contamination by wildlife and livestock. Rodents are treated by growers and buyers as suspects in the food-borne illness matrix. This has resulted in many unnecessary, ineffective, and expensive rodent control practices in leafy green crops. The Metrics require periodic monitoring of animal activity in and around the crop fields, but there are no specific guidelines on how to monitor for rodents. In 2009/2010, we conducted field work in the Salinas Valley region of Monterey County. This included surveying iceberg lettuce and spinach fields to identify the rodents present and test rodent monitoring techniques. As a result of this fieldwork, a specific index of abundance calculation was developed to enable growers to accurately assess the rodent population in their fields. We reviewed the Metrics and identified all portions related to rodents and rodent control. Monitoring techniques were evaluated for their practicality and ability to detect rodents. Control strategies from the California Vertebrate Pest Control Handbook (CDFA 2008) were combined with the results of the monitoring program to create a pocket-sized field guide containing relevant monitoring and control information regarding rodents and leafy green production.
Captive amphibians and reptiles are well-documented sources of human salmonellosis through direct contact with contaminated feces or fomites. However, the relative significance of wild cold-blooded vertebrates as hosts/reservoirs of zoonotic enteric pathogens in their natural habitat is not known. Wild amphibian and reptile populations are present in the leafy green produce production environment in the central California coast, and there are reports from growers that frogs and other species sometimes intrude into produce fields. These intrusions may result in destruction of the crop and economic losses, due to food safety and quality concerns. Environmental groups have also noted potential conflicts between conservation efforts and food safety practices that result in removal or damage to aquatic habitat (e.g., farm ponds, adjacent wetland areas). To address these concerns, we conducted a survey of foodborne pathogen prevalence in common amphibian and reptile populations during the 2011 produce growing season in the central California coast. Preliminary results indicate that Salmonella prevalence was higher among wild-caught reptile (33%) compared with amphibian (4%) taxa. In contrast, all samples were negative for E. coli O157. Wildlife damage management in fresh produce production fields is challenging, due to the diversity of potential hosts/reservoirs of foodborne pathogens and a limited number of mitigation strategies. Professionals working in vertebrate pest control could play an important role in assisting fresh produce growers with implementation of co-management approaches that promote public health and conservation goals in the central coast agricultural landscape.
A Modern Understanding of a Historical Parasite: Food-Borne Risks of Trichinella from California Bear and Feral Pig Populations
Trichinellosis is a zoonotic disease caused by one of the most widely distributed parasite groups in the world, Trichinella. Infection and illness in humans occurs following the consumption of undercooked meat containing larvae. Many cases of trichinellosis go unreported, but symptomatic disease can present with nausea, diarrhea, vomiting, fatigue, and in severe cases, death. Since the eradication of Trichinella from the commercial swine industry, wildlife meat, specifically black bear and feral pig, has become the main cause of human trichinellosis in the United States. California continues to be home to the majority of these cases. Despite this change in epidemiology, few studies have focused on importance of wildlife as a reservoir of human trichinellosis. The most recently reported prevalence estimate of Trichinella in California black bears was over 30 years ago, in 1977. To our knowledge, there have been no published reports on the prevalence of Trichinella in California feral pigs. Furthermore, human, black bear, and feral pig population growth, coupled with increased urban development, has created an expanding ecological niche for parasite transmission, thus increasing the risk of Trichinella infection for consumers of wildlife meat. Given the lack of contemporary data and knowledge, there is a need to generate estimates of the current burden of Trichinella in California wildlife in order to assess the foodborne risk this potentially lethal parasite poses to the public.
Addressing Wildlife Risks in Produce Production in the Central California Coast: A Grower’s Perspective
I provide thoughts about the current situation regarding concern about wildlife contamination of leafy green crops and other agricultural products, potentially leading to food safety risks, from a grower’s perspective. I discuss development of the Leafy Green Marketing Agreement, as well as how buyers are interpreting and reacting to evidence of animals of any kind in growers’ fields. The high economic cost and added risk to growers are important factors, and scientific data to support developing regulations is often lacking.
Comparative Risk Assessment of the First-Generation Anticoagulant Rodenticide Diphacinone to Raptors
New regulatory restrictions have been placed on the use of some second-generation anticoagulant rodenticides in the United States, and in some situations this action may be offset by expanded use of first-generation compounds. We have recently conducted several studies with captive adult American kestrels and eastern screech-owls examining the toxicity of diphacinone (DPN) using both acute oral and short-term dietary exposure regimens. Diphacinone evoked overt signs of intoxication and lethality in these raptors at exposure doses that were 20 to 30 times lower than reported for traditionally used wildlife test species (mallard and northern bobwhite). Sublethal exposure of kestrels and owls resulted in prolonged clotting time, reduced hematocrit, and/or gross and histological evidence of hemorrhage at daily doses as low as 0.16 mg DPN/kg body weight. Findings also demonstrated that DPN was far more potent in short-term 7-day dietary studies than in single-day acute oral exposure studies. Incorporating these kestrel and owl data into deterministic and probabilistic risk assessments indicated that the risks associated with DPN exposure for raptors are far greater than predicted in analyses using data from mallards and bobwhite. These findings can assist natural resource managers in weighing the costs and benefits of anticoagulant rodenticide use in pest control and eradication programs.
The California Department of Fish and Game (DFG) recognizes the need for the availability of a variety of tools for vertebrate pest control and has a strong interest in ensuring that these tools are used in a way that minimizes impacts to nontarget wildlife. From 1992 to 2011, the DFG has investigated 44 cases of wildlife kills caused by vertebrate pesticides, resulting in the loss of 258 animals. While anticoagulant rodenticides were responsible for the loss of the highest number of incidents, incidents involving acute toxicants, such as strychnine and zinc phosphide, typically involved a greater number of animals per incident. Incidents of intentional poisoning of wildlife usually involved strychnine. There were no documented losses due to fumigants; however, such incidents are likely to go unnoticed because the carcasses remain underground.
The United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services (USDA APHIS WS), National Wildlife Research Center (NWRC) “Chemical Effects Database” is an internet-accessible and searchable database that contains bioassay data records for chemicals evaluated for repellency, toxicity, reproductive inhibition, and immobilization of higher vertebrates, and phytotoxicity. These data are of value for environmental risk assessment, conduct of toxicology studies, and the development of safe, effective, and responsible tools to manage vertebrate pest species that cause damage. Chemical screening studies were conducted from 1943 to 1987 by predecessors of the NWRC, and by the U.S. Geological Survey Patuxent Wildlife Research Center (PWRC), formerly the Patuxent Research Refuge (PRR) and part of the U.S. Fish and Wildlife Service. The screening activities were broadly divided into 2 phases. Data collected primarily at the PRR prior to 1960 are published in DeWitt et al. (1953) and Bowles et al. (1974). Research after 1960 was conducted at the Denver Wildlife Research Center (DWRC). Much of these data are also published and now accessible by searching the on-line “Chemical Effects Database” located on the NWRC website (http://www.aphis.usda.gov/wildlife_damage/nwrc/information_services/chemical_effects.shtml). The database search capabilities provide easy access to approximately 11,000 bioassay data records for nearly 2,000 chemicals.
Migration of Brodifacoum and Diphacinone from Bait Pellets Into Topsoil at Palmyra Atoll National Wildlife Refuge
Between June 1 and 30, 2011, a partnership between the U.S. Fish and Wildlife Service, The Nature Conservancy, and Island Conservation successfully implemented a project to remove introduced black rats from Palmyra Atoll National Wildlife Refuge. Prior to the rat eradication, we assessed several environmental risk factors associated with the application of an anticoagulant rodenticide to Palmyra’s emergent land area. Here, we present the findings from a study of toxicant migration from bait pellets into topsoil. Topsoil from plots characterized as “sandy” or “humus” was collected after exposure to bait pellets containing 50 ppm of diphacinone or 25 ppm of brodifacoum. Brodifacoum and diphacinone were detected in samples of both sandy and organic topsoil while control samples collected outside of the study plots tested negative for both toxicants. With both toxicants, residue concentrations decreased with time and neither toxicant was detected in most of the 28, 36, and 50-day samples; trace amounts (=0.2 ppm for brodifacoum and =2 ppm for diphacinone) of the toxicants were detected in a few samples from these groupings. We did not find a significant difference in toxicant concentrations between the two types of topsoil. The results from this study suggest that following a broadcast of rodenticide across Palmyra’s emergent land area, small amounts of brodifacoum or diphacinone would migrate to, and remain in, Palmyra’s topsoil for a short period of time.
Exposure of Wildlife to Anticoagulant Rodenticides at Santa Monica Mountains National Recreation Area: From Mountain Lions to Rodents
A 15-year study of carnivores in an urban landscape in southern California has revealed a high incidence of exposure of non-target wildlife to anticoagulant rodenticides (ARs). All carnivore species studied, including mountain lions, coyotes, bobcats, and gray foxes, have tested positive for exposure to the toxicants. Anticoagulant residues have been detected in post-mortem liver samples at a rate of 83-93% of individuals tested, for coyotes, bobcats, and mountain lions, the three species for which we have extensive sampling. We have also documented mortalities caused directly by exposure to ARs in all four species, particularly in the canids. In both felid species, we found a positive correlation between AR exposure and mange disease, specifically notoedric mange. The incidence of fatal mange infection in bobcats has been at epizootic levels since 2002 in our study area, and more recently outbreaks of the disease have been documented in several other populations in California, all apparently (where testing has been done) in association with exposure to ARs. There are no previously reported instances of epizootics of notoedric mange in any wild felid population. Carnivore exposure to these toxicants appears to be largely secondary (or tertiary, as may be the case in mountain lions) through consumption of their natural prey. In our most recent work, we have evaluated AR exposure of carnivore prey species, including rodents and lagomorphs. We have documented exposure in ground squirrels and woodrats, both of which are regularly consumed by gray foxes, coyotes, and bobcats. Overall, we have found widespread exposure of non-target wildlife to these toxicants, with potentially significant consequences for some species.
Anticoagulant compounds are likely to play an important role in the control of commensal rodents for crop protection and conservation for the foreseeable future. However, there are concerns regarding their persistence and the development of more widespread resistance. We are seeking to retrieve and retain older alternatives as well as developing novel rodenticides. Our three-pronged approach is, firstly, to improve the performance of older non-anticoagulant rodenticides, such as sodium fluoroacetate (1080) and zinc phosphide; secondly to optimise the performance of 1st-generation anticoagulants; and thirdly, to identify alternatives to anticoagulant rodenticides with the same mode of action as para-aminopropiophenone (PAPP), which was registered in New Zealand as a predacide in April 2011. Zinc phosphide was also registered in New Zealand for the first time in 2011, and combinations of ultra-low-dose cholecalciferol with first generation anticoagulants are being advanced to provide the performance characteristics of a 2nd-generation anticoagulant with a lower risk of bioaccumulation and secondary poisoning.
Aluminum phosphide (ALP) is used extensively for burrowing mammal control. However, recent changes have been made to the ALP label which could substantially limit its utility for burrowing mammal control in the future. As such, I developed surveys to help quantify the impact that these changes are likely to have on ALP usage and vertebrate Integrated Pest Management in California. These survey findings were compared to information gathered from the California Department of Pesticide Regulation’s Pesticide Use Report for 2010 to relate the survey findings to the broader spectrum of users throughout California. I found that 49,005 lbs of active ingredient (AI) of ALP was used for burrowing mammal control in 2010, with most applications occurring in residential areas, applied primarily by licensed Pest Control Operators who specialize in vertebrate IPM. Most applications were applied to control pocket gophers, while ground squirrel and mole burrow systems were also treated. Collectively, new buffer and posting restrictions resulted in expected losses of 70% and 26% of agricultural applications of ALP for pocket gophers and ground squirrels, respectively. The impact of restrictions in residential areas may be even more extreme, with estimated reductions in ALP applications ranging from 70-98%. Alternative control methods were typically considered less efficacious than ALP. Furthermore, 13-34% of respondents indicated that they would no longer control these pests in areas where they could not use ALP. Insufficient or ineffective management programs targeted at these pests could result in increased economic damage, greater human health and safety concerns, and increased environmental degradation. Even though ALP has a safe track record in California, ALP users were willing to obtain greater training on its safe use while adhering to a 67% increase in the previous 15-foot buffer restriction, if it meant relaxing some of the current restrictions. Because of the extreme importance of burrowing mammal control, combined with the high efficacy and safe track record of ALP, perhaps these or alternative mitigation steps should be considered to ensure the safe and effective use of ALP. Otherwise, it is quite possible that the estimated 85% reduction in future ALP applications for burrowing mammal control could result in far greater negative consequences than the benefits gained from the new regulations.
Rodenticides are often used to control burrowing rodents but have not been overly efficacious for Belding’s ground squirrels due to poor bait acceptance. This has left alfalfa growers searching for alternative options for controlling this rodent species. As such, we tested aluminum phosphide and gas cartridge burrow fumigation in an alfalfa field in Butte Valley, CA, to determine if either of these approaches were efficacious and cost effective for controlling Belding’s ground squirrels. A comparison of the number of burrows treated and the number of burrows reopened 48-hours post-treatment indicated that both burrow fumigants were highly effective (aluminum phosphide = 94-98%, gas cartridges = 100%). The average cost per application was $1.05 and $2.92 for aluminum phosphide and gas cartridges, respectively. Given the almost 3-fold difference in cost of application between the two approaches, aluminum phosphide appears to be the more practical approach for Belding’s ground squirrel control. Although we currently lack an approach for estimating the amount of damage that Belding’s ground squirrels are likely to cause to an alfalfa field, it seems plausible that burrow fumigation could be a cost effective approach to reduce damage caused by this species, particularly if long-term control can be obtained. Possible long-term management options for Belding’s ground squirrels are discussed.
Potential Fiscal Impact of the Rodenticide Risk Mitigation Decision to the California Department of Food and Agriculture’s Rodenticide Research Program
The United States Environmental Protection Agency (EPA) issued the Rodenticide Cluster Reregistration Eligibility Decision (RED) in July 1998 in response to human health and environmental concerns associated with rodenticides. The EPA and its stakeholders worked for 10 years developing risk assessments and mitigation plans, issuing the final Risk Mitigation Decision (RMD) on May 28, 2008. The RMD restricts retail sale of second-generation anticoagulant rodenticides for commensal use and it refers field use rodenticide registrants back to the RED, which makes those products Restricted Use. This means that all applications of field use products must be made by a certified applicator. These changes have potentially large ramifications for smaller private applicators that are generally not certified to use Restricted Use materials. The California Department of Food and Agriculture, the University of California Cooperative Extension, and the California Department of Pesticide Regulation worked collaboratively to streamline the exam process for private applicators, allowing for a time-limited exam through June 2012. The concern for the Vertebrate Pest Control Research Advisory Committee (VPCRAC) is that many people will not take and/or pass the exam. This will impact the ability to effectively control rodent pests in some areas and may affect the revenue stream supporting the VPCRAC program. Preliminary sales data is not indicative of any impact to the program, but it may be too early to accurately draw any conclusions.
The objective of this study was to determine the effectiveness of Milorganite® as a potential repellent for non-venomous snakes. Milorganite® is the biosolids by-product left from the activated sludge process from the Milwaukee Metropolitan Sewer District. Within a climate-controlled building, two triangular enclosures consisting of panels (2.4 × 1.2 m) resulting in 2.6 m2 floor surface area, were secured to plastic floor covering and provided with cypress mulch and a container of water. Corners of the enclosure were demarcated using a 63.5-mm monofilament line placed 10 cm above the floor, providing a .09-m2 visible triangle of floor surface area. Round metal containers (8.3 × 3.0 cm) were secured to a board and individually placed within each enclosure corner. Treatments consisted of a control, or the addition of 250 mg or 500 mg Milorganite® within respective metal containers, within each corner. Wild-caught snakes (n=20), including rat (Elaphe spp.), corn (Elaphe guttatus), king (Lampropeltis spp.), black racer (Coluber constrictor priapus), and pine (Pituophis melanoleucus) snakes, were placed individually within an enclosure for a 24-hour period. Activity of the snake was digitally recorded using an infrared camera placed above an enclosure. Treatment application was repeated for each individual snake. The amount of time each snake spent within the respective enclosure corners or outside the demarcated areas during the 24-hour period was utilized as an indication of the effectiveness of Milorganite® as a repellent. During the 1440-min trials, snakes spent more time (p<.01) in the control corner (559.9 ± 98.9 min) or outside the demarcated areas (548.49 ± 89.1 min) compared to the 250-mg Milorganite® (214.5 ± 70.1 min) or 500-mg Milorganite® (117.2 ± 21.6 min) -treated areas. While not different (p>.05), there was a trend toward a dose-response effect of the Milorganite® treatment levels. Results of this study indicate Milorganite® demonstrated potential as a snake repellent.
Paraffinized rodent baits developed initially for use in control of Norway rats in sewers by Lloyd Plesse of San Jose, California, an experienced bait formulator for Santa Clara County, significantly enhanced longevity and effectiveness of toxic rodent baits. Within a couple of years, this paraffin type molded bait’s moisture resistant qualities and proven efficacy, especially for sewer rat (Norway rat) control, was the subject of several published articles. Those first three articles, 1959-1961, were responsible for rapidly launching this new paraffinized bait formulation into national usage, at first, mostly by health departments. The structural pest control operators and agricultural interests were soon to follow, using them initially for out-of-doors control of rats and indoors where high humidity normally caused bait deterioration. Recognizing the potential of paraffinized rodent baits, along with the published how-to information, commercial bait manufacturers were quick to get into production and distributors eager to market. Paraffinized rodent baits soon came into common usage and literally revolutionized rodent baits by not only making them more moisture and weather resistant but more convenient to use and versatile in applications. This resulted in greatly expanding the conditions under which commensal rodents could be more effectively controlled. The chronology and evolution of paraffinized rodent baits and their practical uses are followed from their beginning throughout much of their early existence, as are the changes in their manufacturing processes. The factors contributing to development and rapid acceptance for rodent control are enumerated, as are their advantages and disadvantages. The greatest emphasis is placed on the first two decades (1960s and 70s) of the existence of paraffinized rodent baits.
An Assessment of Richardson’s Ground Squirrel Activity and Potential Barriers to Limit Access to Sensitive Sites at Malmstrom Air Force Base, Montana
Small mammals pass through or under chain link security fences, triggering sensors and undermining facility infrastructure at sensitive military sites. Traditional methods of rodent control are not practical because of the vastness of land to be maintained with limited manpower. Permanent barriers (above and below ground) and low-maintenance, long-term bait stations offer potential permanent and cost-effective solutions to mitigate rodent intrusions. We assessed Richardson’s ground squirrel populations, activities, and burrows at Malmstrom Air Force Base, MT. We also conducted preliminary barrier trials in the outdoor rodent buildings of the USDA National Wildlife Research Center in Fort Collins, CO. Ground squirrels were very numerous and active at most sites visited in Montana. Burrows were both simple and short as well some being elaborate and deep (to 5+ ft). Squirrels readily passed through and under the 2-inch mesh chain link fences as well as under site gates. Several effective barriers were identified in pen trials that prevented above-ground and below-ground intrusions. These will need to be field tested. Future studies will investigate designs for a low-maintenance, long-term rodenticide bait stations for deployment at remote sites.
Rats! Foiled Again: A History of Rodent Control Methods Development at the National Wildlife Research Center
The National Wildlife Research Center (NWRC) and its predecessor laboratories have a long history of developing materials and methods for managing rodents and the damage they cause. The NWRC has been influential in exploring, developing, and maintaining legal uses of many traditional field rodenticides such as strychnine and zinc phosphide. Products have been developed for managing rodents in a variety of locales, and for managing a variety of species, from commensal rodents in urban areas, to pocket gophers and mountain beaver in forests, prairie dogs and ground squirrels on rangelands, and nutria and beaver in wetlands. Considerable research has also been conducted on developing methods of managing rodents in underdeveloped countries. Recent efforts by NWRC have focused on development of tools for managing invasive rodents in conservation areas such as island ecosystems and development of alternative, nonlethal control methods.
While it is known that voles will damage seedlings, we do not know the extent to which deer mice and house mice damage seedlings. Knowing this information can assist resource managers in better targeting problem species and implementing appropriate management actions. We planted and monitored ponderosa pine and narrow-leaf cottonwood seedlings in metal stock tanks occupied by deer mice or house mice to assess the potential for damage by these rodents. Both species damaged leaves and stems of cottonwood seedlings, but house mice did more damage. House mouse damage resulted in mortality of over half of the cottonwood seedlings, while deer mice caused a much lower level of seedling mortality. Only slight damage was done by either species to pine seedlings. Neither species damaged the roots of seedlings, despite the extensive burrowing by house mice. While voles are often considered to be the primary rodent species causing seedling damage, we have shown that deer mice, and especially house mice, could also cause substantial damage to deciduous seedlings. However, our work suggests that rodent control to prevent damage to conifer seedlings might not be warranted in general unless extenuating circumstances and the species causing the damage are identified to assist with targeting control methods more precisely.
Many rodent species are effective burrowers. In North America, these include species of ground squirrels, prairie dogs, marmots, and pocket gophers. The burrow systems of other species of rodents such as voles and mice are less elaborate and pose less potential for direct damage. Burrowing abilities, coupled with other characteristics (e.g., prolific, adaptable, ever-growing incisors for gnawing), can result in many types and amounts of impacts to human resources and ecosystems. Damage occurs to levees, roadbeds, buried pipes and cables, intrusion to sensitive areas (such as military sites, capped hazardous waste burial sites), vegetation effects, effects on water infiltration/runoff, and soil erosion. We describe burrow systems of select rodent species of North America and then put them in the context of potential impacts and damage reduction methods. Population reduction with rodenticides and traps are common methods of damage reduction. Non-lethal approaches such as barriers are another method of damage reduction, but these pose many challenges such as effectiveness, durability, and cost. Additional research is needed to better understand rodent burrow systems, impacts of burrow systems, and to improve effectiveness of damage reduction methods. We propose investigations of physical barriers that are effective and economical, and note that a thorough understanding of rodent burrow systems and activities is a prerequisite to the development of effective barriers.
The deer mouse is the most widely distributed and abundant small mammal in North America. They use a wide array of habitats, are very adaptable, and have a high reproductive potential. They play a number of roles in ecosystems, but can cause damage to orchards, forests, agriculture crops, and rangelands primarily through seed and newly-emerged seedling consumption. They also cause damage similar to house mice when they occupy buildings or other structures. Deer mice are important components in disease transmission especially of hantaviruses and Lyme disease. Damage reduction methods generally involve lethal control to reduce numbers using rodenticides and traps. Improvements in control methods are needed, especially in some agricultural crop types.
Resident Canada geese cause substantial economic losses to agriculture and personal property and compromise air traffic safety throughout the U.S. Destroying eggs of Canada geese nesting in the contiguous U.S. is a primary component of the integrated management regime to reduce damage caused by the species. This requires regular searches to destroy eggs throughout nesting season, which may be laborious and costly. Much of the breeding by resident Canada geese occurs on small ponds (≤5 acres). Anecdotal observations suggested that social pressure among breeding pairs of Canada geese typically dictates that only one aggressive breeding pair establishes a territory on small ponds. Using this logic, managers allow a single nesting pair on small ponds and destroy their eggs, while deriving the perceived benefits of the sentinel geese excluding other nesting geese. However, a single pair of geese may also cause damage, decimating plants and depositing accumulations of feces in the localized area. We hypothesized that removal of single nesting pairs of Canada geese on small ponds after the onset of breeding activity would result in a void of geese for the remainder of the reproductive season, thus providing an alternate lower-cost management strategy. We further hypothesized that if the male goose was not removed, he would continue to defend the territory, excluding other nesting geese. Our study was conducted on 22 independent sites with small ponds in Bucks County, southeastern Pennsylvania. Each site held historically one nesting pair of Canada geese. To test our hypotheses, breeding pairs of Canada geese were assigned to one of three experimental groups: 1) control neither female nor male goose was removed, the eggs were treated under normal protocols to prevent hatching, and the nest and eggs were removed after the 28-day incubation period; 2) after nest initiation, only the female goose was removed, and the nest and eggs were removed; and 3) both the female and male goose were removed and the nest and eggs were removed. We determined that targeted removal of a nesting pair or only the female of a nesting pair of Canada geese could be effective in eliminating breeding on a small pond for the entire nesting season. Likewise, the traditional approach of allowing a single aggressive nesting pair on small ponds reliably excluded additional nesting pairs.
Wildlife-aircraft collisions (wildlife strikes) pose a serious safety risk to aircraft. Many bird species, especially gulls, are very difficult to manage within airport environments as many traditional methods (e.g., trap and remove from the airport) can be relatively ineffective due to the birds’ various activities on airports (e.g., feeding, loafing, and flying). Such challenges have greatly impacted the Los Angeles International Airport and the Van Nuys Airport, as documented through historical bird strike records collected since 1990. Using information contained in these bird strike records, USDA APHIS Wildlife Services personnel conducted strategic planning efforts to reduce the risk of bird strikes. Since 2009, efforts have been made to improve the quality of wildlife strike reporting at Los Angeles World Airports facilities through the distribution of bird strike collection kits to airline maintenance offices, subcontract aircraft maintenance companies, and Airside Operations personnel. These kits are intended to facilitate an increase in wildlife strike reporting and the number of wildlife strikes identified to the species level. Following intensive management efforts that included trapping and removal of doves (i.e., rock pigeons, mourning doves), bird strikes by these species have decreased significantly at these airports. Airport-specific integrated wildlife damage management programs at airports that use bird strike information to guide management activities toward problem species have great potential for reducing the risk of bird strikes.
Managing European starlings with DRC-1339 near urban and suburban areas can lead to adverse publicity resulting from encounters by the public with dead and dying birds. Collectors could retrieve the birds, if the likely sites of mass mortalities were known. In December 2009, we radio tagged 50 starlings at 3 sites in central New Jersey and studied their movements and behavior. Two of the sites were ensconced in a mosaic of suburban and urban habitats, whereas the other was in a rural setting. The sites were selected from a list of agricultural producers that had requested assistance from the Wildlife Services program in New Jersey. Starlings using the rural study site showed strong site fidelity (x-bar = 78% of days tracked), stayed closer during daytime wanderings (x-bar = 2 km), and roosted onsite. In contrast, starlings in the urban-suburban mosaic showed less fidelity (x-bar’s = 10% and 36%), wandered farther (x-bar’s = 6 km and 4 km), and seldom roosted onsite. No study sites were visited by members from the other radio-tagged cohorts. Major roosts in the urban-suburban mosaic averaged 10 km (n = 4, SE = 1.4) from the study sites. We predict that most starlings will remain within 6 km of the site during daytime. Poisoned starlings may become lethargic and seek refuge in dense vegetation (e.g., evergreens) near the baited site. Birds >6 km from a bait site are probably on a direct bearing between the bait site and roosting site.
Fruit producers have identified bird damage as a critical issue that has received limited attention from researchers. A USDA study estimated that birds cost producers in seven states tens of millions of dollars through fruit loss and management efforts. Despite these costs, research has been uncoordinated and piecemeal, leaving producers with few, well-tested management options. We describe several objectives to strive for in order to achieve the goal of providing producers with region-specific, cost-effective, and environmentally sustainable bird management strategies. These objectives include 1) quantifying economic consequences of bird damage for producers, consumers, and regional economies, and determining costs and benefits of various management techniques; 2) identifying amounts of damage attributable to specific bird species across crops and regions; 3) determining how bird damage varies within and across spatial scales (orchard, landscape, region); 4) evaluating consumer responses to management strategies and potential effects on marketing; 5) integrating economic, biological, and consumer information, i.e. using a systems approach, to determine the management strategies that should be tested; and 6) testing management strategies for efficacy with replicated, well-controlled experimental designs. By focusing on these objectives and coordinating activities among researchers and extension personnel from different regions of the country and from different disciplines, we will maximize efficiency in addressing this issue on a national scale while providing individual producers with region-specific information to guide their bird management efforts. Communication among researchers, extension personnel, and producers will be critical to minimize the costs of bird damage.
California Gull Predator Management and Reproductive Success of Endangered California Least Terns in the San Francisco Bay, California
Gull predation is known to be an important source of egg and chick mortality for many waterbirds and can have severe impacts on recovery efforts for special status species. We evaluated the effectiveness of California gull management and removal by monitoring tern hatching and fledgling success annually. From 2005 to 2011, nesting success was monitored at a newly established California least tern colony at Hayward Regional Shoreline in San Francisco Bay. No gull management was undertaken prior to 2007. California gulls were the most abundant aerial predator (97%). We recorded 3,769 predatory gull-tern interactions and presumptive take of 26 tern eggs and 23 chicks. Although gull predatory behavior did not change statistically, gull management efforts resulted in significantly improved tern breeding success (measured by number of nests, eggs, chicks, and fledglings). From 2007 to 2011, this colony produced a total of 242 successful nests and 291 fledglings, an average nesting density of 196 nests per ha, and an average of 1.07 fledglings per breeding pair. We discuss difficulties of lethal control of predators, and suggest the importance of human presence for reducing gull predation at the site.
Wildlife-aircraft collisions pose a serious risk to aircraft and cost civil aviation over US$1 billion worldwide annually. Habitat management within airport environments is the most important long-term component of an integrated approach to reduce the use of airfields by hazardous wildlife. Recent research has demonstrated that Canada geese avoid foraging on endophyte-infected tall fescue; consequently, this turfgrass might be useful in airfield revegetation and seeding projects. Although some research evaluating commercially available tall fescue cultivars on airfields has been conducted, additional information is needed to determine if tall fescue cultivars might be viable for airfields in various regions of the U.S. In 2007, a study was initiated to examine the establishment of currently available high-endophyte �‘turf-type’ tall fescue grasses at 9 airfields. The objectives were to: 1) determine if selected tall fescue cultivars establish on airfields across the U.S. and 2) provide airport-specific recommendations for tall fescue cultivar selection. At each airfield, 12 tall fescue cultivars were seeded into 3 replicate experimental plots in either fall of 2007 or spring of 2008. Although tall fescue cover varied among airports, most cultivars resulted in similar amounts of tall fescue cover after one or two growing seasons. This study demonstrates and identifies tall fescue cultivars that will grow successfully in the environmental conditions found on these airfields while providing airfield vegetation that is minimally attractive to wildlife hazardous to aviation.
Feral cats have flourished in urban areas of Hawai´i due to the state’s favorable climate and people’s positive perception of cats. However, the presence of large numbers of feral cats has raised concern both in terms of predation of native species and as vectors of disease. One disease, in particular, that has aroused a great deal of attention is toxoplasmosis, caused by the Toxoplasma gondii parasite. Cats are the definitive host of T. gondii and concerns arise regarding transmission to humans due to the relationships people have with cats. Another concern is the fact that the parasite has infected endemic and endangered species found in the state. Toxoplasma gondii oocysts are shed in cat excrement and can persist in soil between 1 and 4 years. The presence of T. gondii at cat colony sites could be an important factor when making decisions for the management of feral cats in the state. We intend to test soil samples taken from cat colony sites at the University of Hawai´i at Mânoa for T. gondii oocysts using molecular identification methods. Cat colony sites are defined by feeding stations maintained by cat colony caretakers. Given that cats are definitive hosts of T. gondii, we hypothesize that the presence of toxoplasmosis in soil is correlated to cat colony locations. Because most cats within a colony remain in close proximity to their feeding location, we predict that toxoplasmosis is spatially contained within tight proximity to cat colonies. If T. gondii oocysts are present in soil at the University of Hawai´i at Mânoa, then cat colonies may cause potential health hazards for landscaping personnel, students, staff, and visitors.
Old World Hantavirus Infection in Rattus Species and Risk Management in Urban Neighborhoods of New Orleans, Louisiana
Hantaviruses are lipid-enveloped, tri-segmented RNA viruses belonging to the family Bunyaviridae. Hantaviruses are divided taxonomically into Old World and New World groups that typically cause hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome, respectively. Each hantavirus is specific to a rodent reservoir host. In 1983, isolation of an Old World hantavirus similar to Seoul virus (Tchoupitoulas virus) occurred from rats caught in New Orleans, Louisiana, but to date, this virus has not been associated with human disease. Since that time, no hantavirus surveillance has been conducted in this geographic area. We sought to determine if Old World hantaviruses still circulate in rodents in New Orleans and, if so, to decrease rat populations to reduce the risk of human-rodent interaction and the potential for disease transmission. Over a 3-year period, rodents were live-trapped using Sherman and Tomahawk traps. Blood and other tissues were collected and samples tested for the presence of Old World hantaviruses via Reverse transcriptase Polymerase Chain Reaction. Trap sites were identified through selected citizen service requests and routine municipal rodent management activities. Of the 172 roof rats and Norway rats collected, 3.6% tested positive, indicating continued presence of Old World hantaviruses in New Orleans. This study raised awareness of the continued risk of rodent-borne disease in the greater New Orleans area and spawned proactive management strategies on a city-wide basis, including neighborhood surveys, public education and awareness campaigns, and an aggressive rodenticide baiting program in areas with large rodent populations. Continued surveillance and detection of hantaviruses and other rodent-borne pathogens will help preserve the safety and health of New Orleans residents.
Dynamics of Rodent-Borne Zoonotic Diseases and Their Reservoir Hosts: Invasive Rattus in South Africa
Lack of adequate sanitation and pest control, and poor housing conditions that prevail in much of both rural and urban South Africa, cause rodent populations to thrive, promoting contact with humans, which results in increased risk of zoonotic disease transmission. This study focused on bacterial pathogens involved in potential zoonoses present in three commensal and invasive Rattus spp., namely Rattus norvegicus, R. rattus, and R. tanezumi, from rural and urban South Africa. Bacterial prevalence and diversity was determined through amplification and sequencing of the mitochondrial 16S gene region, using four primer sets: two that have a broad bacterial species recognition range, and two genus-specific sets that target the genera Streptococcus and Streptobacillus. An overall bacterial prevalence of 32% (n = 84) in kidney samples was obtained using the 16S universal primer sets. Subsequent sequence analyses found bacterial prevalence per host species to be 41% for R. norvegicus, 42% for R. rattus, and 8% for R. tanezumi, with representatives of diverse bacterial taxa such as Clostridium sordelli (toxic shock syndrome), Bacillus cereus (diarrhoeal disease), and Enterococcus faecalis (nosocomial infections) being characterised. The primer set targeting Streptobacillus moniliformis was used to determine the prevalence of this zoonotically-important bacterial taxon, which is transmissible via a bite from Rattus to humans, whilst Streptococcus-specific primers were used to assess environmental shedding of this agent via the urinary route. The results highlight the public health implications especially for immune-compromised individuals, as these rodent-borne pathogens can cause opportunistic infections that in such individuals are not readily diagnosed or treated.
Striped Skunk Relative Abundance in Flagstaff, Arizona: Implications for Rabies Spread and the Current TVR Program
Potentially fatal wildlife diseases like rabies are of increasing concern, due to human effects on the environment that could alter wildlife behavior and population dynamics in ways that increase disease prevalence. Wildlife population abundance is a key factor, affecting both disease outbreak and rate of disease spread, and understanding how population abundance changes across landscapes is crucial for developing predictive models to control and manage wildlife diseases. We investigated how urbanization in Flagstaff, AZ influenced skunk population abundance by simultaneously trapping 6 pairs of suburban and wildland study sites for 200 trap-nights between June and September 2011. The number of unique skunks captured at the 6 suburban locations ranged from 3-14 (mean = 6.5) while the number trapped at the 6 wildland sites ranged from 0-2 (mean = 0.5). We also reviewed data gathered as part of the trap-vaccinate-release (TVR) program carried out from 2004-2010 by USDA APHIS Wildlife Services to estimate population sizes and the percentage of the population vaccinated. Our estimates of the percentage of the population vaccinated in any one year ranged from 11%-23%, below percentages reported in the literature as necessary to prevent disease spread. Overall, these data indicate that the potential for disease spread was greatest within the suburban matrix and relatively low in surrounding wildlands and that intensified annual TVR programs would be necessary to maintain high enough percentages of immunized animals to achieve effective herd immunity.
Changes in Possum Den-Site Use Following Density Reduction: Implications for Conservation and Bovine Tuberculosis Control
The Australian brushtail possum is a pest in New Zealand, as it has caused the decline of a number of native bird species and has become the greatest barrier to the eradication of bovine tuberculosis (bTB) from livestock. As such, possum populations are reduced (i.e., controlled) at a cost of millions of dollars every year. Yet, control is still timely, costly, and not always 100% effective. Behavioral changes in possums have the potential to substantially affect the ability to control possum populations. For example, it is currently unknown whether possums change their behavior, such as den-site use, following control. How possums use dens is an important consideration in controlling bTB, as dens are a potential infection reservoir for both possums and livestock. Knowledge of any changes in den-site use may allow the design of more targeted and efficient control operations that identify potential increases in transmission risk. To investigate changes in den use due to control, possums were fitted with VHF devices, and were tracked to their den sites before and after a control operation that killed approximately 54% of the adult population. The total number of dens they used and the number of times they changed dens were recorded. Density reduction resulted in an increase in the number of times possums changed dens. However, den use was more strongly influenced by the sex of an individual, with males changing their dens more often than females. Density reduction did not appear to result in a change in the number of dens used. Instead, this behaviour was also largely driven by the sex of an individual, with males using more dens than females. This potential increase in transmission risk does not mean that control strategies should not be undertaken, but that managers should keep in mind the likely responses of possums to control and adapt their strategies accordingly. For example, control measures may need to be targeted towards those individuals that use more dens, such as males. This research also further highlights the need for efficient control that reduces populations to very low densities, to negate this potential increase in transmission risk.
To achieve long-term suppression of pest populations, devices capable of continued control over extended timeframes are needed. Creating new pest management tools to achieve this goal requires the integration of animal ecology, toxicology, and design engineering. This research outlines the development and testing of a long-life, resetting, toxin delivery system for vertebrate pest control, coupled with advances in novel species recognition systems. Such devices have the potential to offer advantages over current labor-intensive control techniques. Resetting systems have been developed to target several of the most destructive vertebrate pest species in New Zealand, including stoats and weasels. Results of enclosure trials for these two species showed similar responses after a paste containing 40% para-aminopropiophenone was delivered onto the chest and stomach, following triggering by a treadle operated system. Both species groomed the paste off shortly after application and death occurred after an average of 42 minutes for stoats and 57 minutes for weasels. The applications of these resetting devices are now being extended for the control of brushtail possums, another major vertebrate pest in New Zealand. Coupled with this, developments in species identification systems are ensuring that risks to non-targets are substantially minimized. Resetting, long-life toxin delivery systems could be deployed to control a variety of pest species, and further enhancement of these tools are ensuring their use for widespread field applications in a cost-effective, safe and reliable manner.
Hemlock Farms Community Association (HFCA) is a >4,500-acre private, gated community located in Pike County, Pennsylvania, established in the 1960s. During our study, 3,150 homes existed in HFCA, with 400 more homes expected to be built in the future. In recent years, the community took proactive steps to coexist with white-tailed deer in the community. Residents were fully involved in deer management decision making early in the process. Through the Pennsylvania Game Commission Deer Management Assistance Program, HFCA has allowed hunting by residents in undeveloped areas of the community to assist in reducing and maintaining deer densities. Non-lethal techniques to prevent browsing of the forest understory and landscape vegetation by deerother than fencingwere ineffective. U.S. Department of Agriculture Wildlife Services was consulted in 2005 by HFCA to initiate an integrated white-tailed deer damage management program to reduce damage to forest regeneration and landscaping, and to protect human health and safety. In October 2005, we began lethal deer removal via sharpshooting to reduce the deer population to 10 deer per square mile of forested habitat (50 deer) from an estimated =125 deer per square mile of forested habitat. By winter 2009-2010, we removed a total of 830 deer, bringing the population within the management goals of the community. The forest understory rebounded, deer-vehicle collisions were reduced to an annual level of near zero. Physiological indices suggested that the health of deer improved as population densities were decreased. Residents voted annually on a referendum to continue culling of deer. Therefore, monitoring of the deer population and education of residents will remain important components of the deer management regime.
Many natural resource agencies are managing white-tailed deer populations in suburban areas and require information about deer populations, deer impacts on vegetation, and human preferences toward deer and deer management to support decision making. We utilized a multi-faceted approach to investigate common obstacles in suburban deer management and discuss findings from our study based in the Chicago Metropolitan Area during 2007-2011. We discuss the need for managers to examine suburban deer populations and management issues at a broader scale (i.e., countywide versus single community) and promote proactive deer management in lieu of the conventional paradigm of beginning management only when deer populations have become overabundant. Discussion topics include practicality and costs of deer density estimation and herbivory monitoring techniques over multiple plant communities and numerous study sites. In addition, we illustrate how a comprehensive human dimensions survey can identify determinants that contribute to the public’s perceptions of deer density and assess the acceptability, conflict, and beliefs regarding deer management methods. Lastly, we describe the relationship between landscape characteristics and deer density; this information can be utilized to determine suburban lands that may be prone to high deer densities and inform land management practices. Our work provides suburban natural resource managers with techniques to identify management practices supported by their public constituents and information useful for managing deer populations.
The Wildlife Damage Management program in Fresno County, California, which assists landowners with solving problems regarding property damage, crop, poultry, and livestock losses, and public health threats, is described. While historically, coyote control account for approximately 90% of the program’s effort, recent increases in wild hog damage have made it necessary to expend 40% of all efforts on this species. Beaver control effort are ongoing, and local mosquito abatement districts have requested beaver removal in order to eliminate mosquito habitat, as part of an effort to reduce the incidence of equine encephalitis and West Nile virus. Changes in beaver control strategies are described.
The Invasive Animals Cooperative Research Centre (IACRC) has developed an end-user centred information toolkit based on developing and implementing best-practice regional and local management strategies for pest animals. The PestSmart Toolkit has consolidated the latest knowledge on strategic planning and management of major Australian agricultural and environmental pest animal species, combined with product use manuals, case-studies, fact-sheets, guidelines and extension materials including videos and social networking. Much of this has been derived from the IACRC’s 7-year (2005-2012) research and development program, but the Toolkit also adopts prior best practise techniques and knowledge where appropriate. All PestSmart Toolkit products and publications are freely available online at www.feral.org.au/pestsmart/. A great deal of information is already live and more is on the way. Users can browse the information based on pest species of interest, type of information required (e.g., policy and legislation, management, maps, images), or information relevant to different groups of people (land managers, regional/natural resource managers, policy makers). The PestSmart Toolkit formed the basis of a nationwide PestSmart Roadshow, conducted in all state and mainland territories of Australia between January and June 2012. Roadshow events have directly demonstrated the PestSmart Toolkit, along with the use and benefits of the new and soon to be registered pest animal control products and techniques available to land managers. The overall process, which combined the establishment of the PestSmart website, 60+ factsheets and case studies, Facebook and Twitter accounts, YouTube channel, 20-stop national PestSmart Roadshow day-long events, and promotional material, has been incredibly well received and has significantly changed the face of pest animal management in Australia. This has been indicated by participant feedback, website usage, and new product sales. The PestSmart approach is recommended for other states or countries interested in reinvigorating the overall public morale and participation in pest animal control.
Training in vertebrate pest management is in a parlous state worldwide. The level of retained corporate knowledge is continually declining as many senior pest managers leave the workforce and take the skills gained through years of experience with them, leaving a vacuum of appropriate skills in vertebrate pest management. There is a serious lack of training in vertebrate pest management at undergraduate or postgraduate level, and even less that is based on current best practice. In 2008, the Diploma in Conservation and Land Management (Vertebrate Pests) was developed in consultation with state government pest agencies to provide field officers with the skills needed to develop and implement strategic pest management plans. The course is based on the principles of the Australian Pest Animal Strategy and uses case studies from successfully operating programs to explain strategic management of pests. The course is offered through flexible on-line delivery supported by workshops, allowing students to study remotely without having to regularly attend a classroom. In 2010, the Graduate Certificate in Wildlife Management (Invasive Animals) was developed through the University of Canberra. It provides mid and upper level land managers with the skills to identify pest animal problems and develop and implement effective pest management strategies based on best practice. This course is offered through flexible on-line delivery and encourages students to incorporate pest animal management problems faced in their workplace into their studies. For land managers wishing to extend their qualifications in wildlife or pest management past the graduate certificate stage, the University of Canberra is developing graduate diploma and Masters level courses. These higher level qualifications will be designed following input from industry and should be able to be tailored to the individual needs of students.
Principles contained in the 1993 publication “Managing Vertebrate Pests: Principles & Strategies” were developed during a review of past and current pest management practices. They were used to guide the development of a series of management guidelines for our major vertebrate pests – feral pigs, house mice, European rabbits, red fox, feral pigs, feral horses, wild dogs, and carp. The principles have been constantly refined through subsequent on ground experience in working with stakeholders to implement best practice management programs for pest animals. In this paper, we present what we now consider the seven principles that underpin best practice management of pest animals. They are: 1. A pest is human construct. 2. All key stakeholders need to be actively engaged and consulted. 3. Rarely can pests be eradicated. 4. Most pest management needs to focus on the outcome, reduction in damage, not just killing pests. 5. A whole-system approach is required for managing pest damage. 6. Most pest management occurs in ecosystems in which our knowledge is imperfect. 7. An effective monitoring and evaluation strategy is essential for all management interventions. Together, the principles comprise the strategic approach to pest management. We explain the rationale behind these principles and illustrate them with examples.
The mission of U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services (WS) is to provide federal leadership and expertise in managing problems caused by wildlife. Approximately every 5 years, WS conducts a research needs assessment (RNA) to help to align research priorities at the National Wildlife Research Center (NWRC, the research arm of the WS program) with WS program and customer needs. In 2011, the WS Deputy Administrator solicited input from employees throughout the WS program and representatives from other federal agencies, all 50 state wildlife agencies, various livestock and agricultural commodity groups, and non-governmental organizations. Eighty-six federal employees from 36 states and the District of Columbia and 31 non-federal employees from 20 states responded to the RNA survey. Aviation safety, zoonotic diseases, livestock predation, and to a lesser degree protecting threatened and endangered (T&E) species and reducing crop depredations, were projected to be major areas of concern during the next 5 years. Invasive species, specifically feral swine, were one of the most frequently identified areas where research is needed. Development of nonlethal control methods and economic assessments were given a high priority. Many respondents wanted economic justification for their organizations or programs. Protection of aquaculture, property, and human safety, and development of vaccines and repellents were more localized concerns. Predation on livestock (especially cattle and sheep) and big game, waterfowl, and upland birds was a much bigger concern in the Western Region (WR) than the Eastern Region (ER). A higher percentage of WR respondents also anticipated being more involved in conflicts involving birds. Cormorants, beavers, deer, and especially vultures were of higher concern in the ER. State agency and private stakeholders most frequently identified either wildlife transmission of diseases or livestock depredation as their highest area of concern. State agency and private stakeholders most often identified development of more effective management techniques as their highest research priority. All respondents expressed a need for better economic information about the extent and nature of various human-wildlife conflicts. The results of this RNA, along with guidance from Congress and the WS Deputy Administrator and stakeholder input, will help establish WS research priorities.
Over the past 20 years, the issues and species involved in wildlife damage management have changed in nature and magnitude. I present a compilation of wildlife damage data collected from Alabama Cooperative Extension System agents in 1990 and 2011. In 1990, snakes and commensal rodents were the cause of most wildlife damage complaints. While these two groups were still listed in 2011, armadillos, gray squirrels, white-tailed deer, and wild pigs (previously unranked) took the top four rankings. The nature of complaints within a species category showed some changes with traditionally rural/agricultural species now being of concern in suburban/urban situations. Documentation of these changes in species and types of complaints provides us with information to predict future issues related to wildlife damage.
Often the greatest challenge in wildlife management is not the management of the animals themselves, but rather the human component of human-wildlife conflict. Persuasive and emotional dialogue is extensively used by private organizations and groups to promote specific agendas. In contrast, a persuasive educational format is often used by science-based groups to promote an agenda. We investigated the effects and importance of word choice using surveys involving wildlife and environmental issues. While topics were identical, survey questions were written to be Persuasive Educational or Persuasive Emotional in structure and were administered to students and to faculty-staff of Berry College. Based on results of surveys completed (n=568), responses could generally be manipulated depending on textual format. However, significant direct exposure to wildlife on the Berry College campus may have influenced the degree of manipulation achieved among both groups of respondents. Results of the study demonstrate the importance of word choice in influencing perspectives. Clearly understanding the perspectives and attempting to identify likely experiences of an audience is essential in order to effectively use written and/or oral delivery of information to achieve public support.
Declines in hunter recruitment coupled with dramatic growth in numbers of white-tailed deer (Odocoileus virginianus) have challenged our ability to manage deer populations through traditional methods. We surveyed all state wildlife agencies and estimate the abundance of white-tailed deer in North America currently exceeds 30 million. Traditional methods of population management have been ineffective in reducing numbers of deer sufficiently in some environments. The only way to manage overabundant deer directly, cost-effectively, and in a timely fashion is through lethal methods. States currently are issuing record numbers of permits to hunters to increase harvest of white-tailed deer. Unfortunately, hunter participation has been declining in North America during the past two decades. Regulated commercial harvest would help state wildlife agencies manage overabundant populations of white-tailed deer andallow hunters to sell all orparts of harvested deer. We anticipate that many will criticize regulated commercial harvest of deer and claim that it is contrary to the North American Model of Wildlife Conservation (NAMWC). We can, however,argue that regulated commercial harvest meets all seven of the pillars of the NAMWC: 1) Wildlife is a natural resource of the public trust(state wildlife agencies willmanage deeranddeerwould continue to be a public resource). 2) No commercial use of wildlife [a direct reaction to exploitive and unsustainable market hunting in the 18th and 19th Centuries; commercial markets currently exist for other natural resources (e.g., furbearers, fish, timber); contemporary conservation values would not allow overexploitation; a framework for regulations, monitoring, and enforcement already isin place in every state]. 3) Democratic rule of law to regulate use of wildlife (commercial harvest of white-tailed deer would be highly regulated by wildlife agencies through public processes). 4) Hunting opportunity for all (anyone legally able to hold a deer hunting license would be eligible to apply for a Commercial Deer Harvest License (CDHL), CDHL programs would be implemented only where recreational hunting is proven inefficient or inappropriate). 5) No frivolous use of wildlife (CDHLs will beused to generate of food and other products, management would address risk to human health and safety andlosses ofagricultural resourcesto deer). 6) Wildlife is an international resource (has little to do with our proposed idea of managing overabundant resident populations of white-tailed deer, but a CDHL program may be applicable to any overabundant species, including internationally migratory species,such assnow geese,Chen caerulescens). 7) Science-based wildlife policy (a CDHL program would rely on science and research-based data to estimate densities before, during, and after commercial harvest). A CDHL program should be managed and distributed by state wildlife agencies, issued only to qualified individuals, enable harvest of an allotment of deer in areas targeted for population reduction, and permit the sale of whole carcasses and parts of harvested deer. Administration of a CDHL program will be taxing. State agencies alreadyareunderstaffed, but administrative and enforcement frameworks already exist for commercial harvest of publicly owned natural resources (e.g., furbearers, fish, timber) and the processing and handling of meat (e.g., USDA inspections). Revenue generated by CDHL programs could be directed back toward agencies and personnel who will administer and oversee these programs. Looking forward, we anticipate several issues mustbe addressed for regulated commercial harvestof deer to be accepted by agencies, hunters, and the public. The dogma against commercial use of wildlife may be well established. It may be difficult to mediate changesin attitudes in the wildlife community, stakeholders, and other publics. It will require adoption at all levels. State laws and regulations will need to be reviewed and some will have to be changed. Some will argue that we do not have the strength, stamina, or political will necessary to implement such broad sweeping changes. On the other hand, many wildlife managers will appreciate having an alternative tool for managing overabundant populations of white-tailed deer. We identified several benefits (reduce overabundant populations of deer; source of healthy, natural, green, locally-produced protein; economic growth, entrepreneurship, and market expansion; and public engagement and appreciation) and expected concerns associated with this concept(privatization of wildlife; overexploitation; food safety; competition with existing commodities; law enforcement; challenges of changing laws, regulations, and attitudes). We encourage a professional discussionof regulated commercial harvestto address the issue of overabundant white-tailed deer.
The Alaska Department of Fish and Game’s (ADF&G) Division of Wildlife Conservation personnel routinely respond to situations in which they must safely and effectively modify an animal’s undesirable behavior or restrain an animal to allow for a rapid disentanglement, injury assessment, or other short-term intervention. In hazing or aversive conditioning situations, traditional methods and tools may fail to correct the undesirable behavior and lethal force may be the only option left. Incapacitating drugs are routinely deployed for restraint and have a good safety record, but can be time consuming and carry inherent risks to the animal both from the delivery systems (e.g., puncture of vital structures) or the drugs themselves (e.g., overdose or other adverse drug reaction and, in some cases, a prolonged recovery period possibly leaving the animal more susceptible to environmental hazards and predators). There is also the risk of accidental human exposure to the drug through the handling and delivery process and in bounced and/or unrecovered darts in residential and other high public-use areas. The use of electricity for wildlife mitigation is not a novel concept. Electric fences for animal exclusion and captivity are widely accepted and in common use. Hand-held electric jab-sticks have also been routinely used in both domestic animal and captive wildlife facilities since the 1950s for staff protection. However, the use of portable, targetable, distance-delivered electronic systems designed to incapacitate and cause noxious stimuli for hazing or aversive conditioning is a new concept in wildlife management, and is based on the modern TASER® Electronic Control Devices (ECD). Law enforcement officers have used these devices for over a decade to safely gain control of non-compliant, combative, and suicidal persons. We present 11 cases of the use of an ECD in the management of common wildlife-related calls for service to ADF&G. This case series demonstrates that ECDs may have a role in wildlife management for 1) temporary restraint and control, 2) hazing and/or aversive conditioning, and 3) personnel safety.
Evaluation of a Pressurized Exhaust Device to Control Pocket Gophers and Belding’s Ground Squirrels in Alfalfa
Intermountain alfalfa fields are ideal habitat for burrowing rodents like pocket gophers and Belding’s ground squirrel, due to an alfalfa stand life of at least 5 to 7 years and sprinkler rather than flood irrigation. Current control measures are only marginally effective and are expensive or extremely labor intensive, so many alfalfa producers have no rodent management program whatsoever. A new device called the Pressurized Exhaust Rodent Controller (PERC) was developed to control burrowing rodents using an internal combustion engine to generate and pressurize carbon monoxide that is injected into the burrow system using multiple hand-held probes. Field trials were conducted in April and May 2006 to evaluate the effectiveness of this device for controlling both pocket gophers and Belding’s ground squirrels in Siskiyou County, CA. An additional gopher control study was conducted in October 2011 to evaluate a newer version of the PERC device. Gopher studies were conducted in three commercial alfalfa fields and ground squirrel studies in an alfalfa field and a dryland range field. The PERC unit was used to inject exhaust fumes into the gopher burrow system. Approximately 24 hours after treatment, the gopher burrow systems were opened. Control was estimated by assessing the number of burrow systems that remained open the following day. Using the open-hole index technique to assess gopher activity, control efficacy was calculated to be 61%, 63%, and 45% for the two 2006 studies and the 2011 study, respectively. In the Belding’s ground squirrel studies, the hand-held probes were inserted into the open burrows and the burrow opening closed with soil prior to injecting the carbon monoxide exhaust. Control was assessed by determining the percentage of burrow systems that were reopened the day after treatment. Control efficacy for the two squirrel studies was calculated to be 81% and 71%. These preliminary results suggest that the injection of pressurized exhaust in gopher and squirrel burrow systems may be effective as part of an integrated vertebrate pest management program, but additional research is needed to further define the parameters required for effective control.
Feral swine populations are expanding throughout the U.S., where they are causing increasing amounts of damage to agriculture, natural resources, and property and threaten human health and safety. Methods to control feral swine damage in the U.S. consist of integrated fencing, trapping, snaring, and shooting (including hunting with dogs) efforts. New methods that are being developed to control feral swine damage include toxicants and fertility control agents. For these emerging technologies to be effective at the population-level, they must function through oral routes of delivery. Concurrent to the development of orally-delivered actives, a cost-effective system that delivers biologics to feral swine while restricting access to non-target wildlife, needs to be developed. Our objectives are to 1) describe historical efforts to develop a feral swine-specific oral delivery system in the U.S., 2) present preliminary findings from an ongoing collaborative evaluation of the Australian-made HogHopper™, and 3) outline future opportunities in developing a feral swine-specific oral delivery system. While there is a real need for a feral swine-specific oral delivery system, presently there is no universally effective system suitable for all applications and field scenarios. Each system has its advantages and disadvantages that must be assessed within its management context.
White-tailed deer damage urban and suburban plantings as well as crops and stored feed. A high public demand exists for non-lethal control methods. Several frightening devices are available for deer and all can be categorized as auditory, visual, tactile, and biological. Several problems exist with frightening devices, including: effectiveness, acclimation, cost, and acceptance. We tested the efficacy of a frightening device that played pre-recorded distress calls of adult female white-tailed deer when activated by an infrared motion sensor. Potential benefits of the device are that deer are less likely to acclimate to animal-activated and infrequently projected calls and that distress calls may elicit a stronger and longer lasting response. We tested the product in DeSoto National Wildlife Refuge (DNWR) in eastern Nebraska and western Iowa during late winter 2010. We established 3 treatment sites and 3 control sites, each being 0.004 ha and located >0.6 km apart. At each site, we deployed deer-activated bioacoustics devices and motion-activated cameras to record deer responses to the devices. We maintained one 13-day pretreatment period (10 Mar - 22 Mar) and one 13-day treatment period (23 Mar - 4 Apr) and recorded breaches and feed consumption. The deer-activated bio-acoustic frightening device reduced deer entry into protected sites by 99.3% (ä = -558.00, P = 0.089) and bait consumption by 100% (ä = -75.20, P = 0.064). Unfortunately, small sample size (n = 3) and a natural decline in motivation of deer to access bait due to spring green-up diminished the statistical significance of results. The deer-activated bioacoustics device was effective, deer did not acclimate to the device, and the device was not invasive. The frightening device we evaluated demonstrated potential for reducing damage in disturbed environments and agricultural settings. The device currently is being marked as DeerShield by BirdGuard (http://www.deershieldpro.com/).
Rodent populations at airports can cause human safety issues by attracting raptors which increases the risk of raptor-aircraft strikes. Various methods can be used to reduce rodent numbers, including trapping, poisoning, and habitat manipulation. Burrow disruption by turf rolling and soil aeration is a potential habitat manipulation method that could potentially reduce the carrying capacity for rodents. We tested this method at Kansas City International Airport, Missouri. We monitored the rodent populations in a control (untreated) area and in a nearby treated area where the turf was rolled and the soil aerated. We used grids of live traps to determine rodent abundance in the two areas. Unfortunately, the turf rolling and aeration did not reduce the rodent population, as we recorded 14-15 rodent captures per 100 trap-nights on both areas. We caution, however, that this was a very preliminary assessment, and the method could be further investigated for its potential to reduce rodent populations.
Throughout the past several decades, coyotes have become common inhabitants of urban areas in the southeastern United States. Because their southward expansion is recent, there is a lack of information on activity patterns of urban coyotes in the Southeast. We trapped and radio-collared 20 coyotes to determine seasonal activity patterns along an urban-rural gradient in east-central Alabama during 2007 - 2009. We created an urban-rural gradient based on percentage of urban land-cover in home ranges. Percentage of urbanization in home ranges was 2% - 45%. Mixed logistic-regression models indicated that coyotes along the gradient were active at similar times during all seasons. Information presented in this study will allow biologists and resource managers to gain an understanding of movements of coyotes in urban areas and will be helpful in predicting and mitigating potential human-coyote interactions in the Southeast.
The San Joaquin kit fox is listed as federally Endangered and California Threatened, primarily due to habitat loss from agricultural, industrial, and urban developments. However, a population of kit foxes estimated at 200-400 persists within the city of Bakersfield, CA. This population appears to be demographically robust with a high probability of persistence. Thus, this population potentially could contribute to range-wide conservation and recovery efforts. The presence of this population in an urban environment creates management challenges. Management issues include human and pet safety, dens in inconvenient locations, and carcass disposal. Resolution of these issues generally is not difficult. Conservation challenges include roads and vehicles, rodenticides and other toxins, sports netting, den destruction during routine maintenance operations, interspecific competition and disease transmission, movement corridors, and regulatory policy. Although the Metropolitan Bakersfield Habitat Conservation Plan provides protective measures for kit foxes during new construction, such measures do not extend to operations, maintenance, and other routine activities. Furthermore, formal policies regarding management and conservation of urban kit foxes have not yet been developed by the U.S. Fish and Wildlife Service and California Department of Fish and Game, resulting in inconsistent responses to urban kit fox issues. Based on a public opinion survey, Bakersfield residents generally support conservation of urban kit foxes. Successful resolution of management issues will minimize conflicts and enhance efforts to conserve kit foxes.
The objective of this analysis was to estimate the net benefits of controlling bird and rodent pests in California production of wine grapes and avocados. These two crops were chosen because of the expected differences in types and extent of pest damage and methods of pest control used by growers, as well as their importance in California agriculture. A web-based survey was designed to capture grower experiences with current levels of pest damage and their expectations about damage levels without control. Information on the methods of pest control and associated costs was also solicited from growers. We obtained 83 responses from avocado growers and 84 responses from wine grape growers. Results indicate that rodenticide use and trapping are the predominant methods of rodent control in both crops, while netting and visual scare devices are the most common methods used to control birds. The net benefits of bird and rodent control were measured on a per-acre basis and accounted for crop savings, avoided property damage, and control costs. In avocado production, the net benefit of bird control was estimated to be $60 to $196 per acre, and the net benefit of rodent control was estimated to be $574 to $1,117 per acre. In wine grape production, the net benefit of bird control was $956 to $1,600 per acre and the estimate for rodent control was $390 to $832 per acre.
This study focuses on how vertebrate herbivory affects the reproductive success of Morefield’s leather flower, Clematis morefieldii, from plant emergence in spring to after fruit dispersal in autumn. Morefield’s leather flower is an endangered perennial vine found in only three counties in northeast Alabama and south Tennessee. High levels of vertebrate herbivory damage have been observed on these plants. Suspected leaf and seed herbivores include white-tailed deer, rabbits, and small rodents. High levels of herbivory have the potential to reduce plant vigor, fruit production, and regeneration, thereby posing a serious threat to the future viability of plant populations. Herbivory studies include a reproductive attrition and post dispersal achene predation study along with herbivory surveys at all accessible sites. The reproductive attrition and post-dispersal achene predation studies are all conducted at a large population in Madison Co., AL, and the herbivory surveys should give insight into whether or not similar herbivory problems are occurring at other populations. The reproductive attrition study documents the number of flower buds producing achenes and also records the probable cause for those buds that were not successful. Vegetative herbivory has also been recorded for plants in the reproductive attrition study in an attempt to correlate high levels of herbivory with reduced reproductive effort. Achenes in the post-dispersal achene study are being eaten by unknown herbivores, and documentation of these herbivores is being attempted. Information gathered in this study will allow managers of this species to understand some of the factors that ultimately can limit the long-term viability of Morefield’s leather flower populations.