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Open Access Publications from the University of California


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:

Marsh, Rex E.  2008.  A History of the Vertebrate Pest Conference.  Proc. Vertebr. Pest Conf. 23:310-326.

Gorenzel, W. Paul.  2004.  Opening Remarks - A Retrospective Look at the Vertebrate Pest Conference.  Proc. Vertebr. Pest Conf. 21:1-2.

Howard, Walter E.  1982.  Twentieth Anniversary of Vertebrate Pest Conferences in California.  Proc. Vertebr. Pest Conf. 10:235-236.

Howard, Walter E.  1962.  Opening Remarks – Vertebrate Pest Control.  Proc. Vertebr. Pest Conf. 1:1-7.


Breathing lessons

Current issues in wildlife damage management and the protection of human health and safety arise from the successful application of traditional methods by state and federal managers. The paradox is that these same methods are increasingly controversial. Within this constraint, management strategies may be difficult to implement. In California, for example, protecting state-threatened foxes could mean killing federally protected golden eagles. In Utah, restoring Gunnison sage grouse may require the sustained lethal suppression of predator populations unless or until habitat can be restored. The obvious fact is that these are unpopular choices, and special interest groups frequently oppose selective intervention, promoting instead somewhat neo-Romantic interpretations of ecosystem management. Luckily for the species involved, the motivating biological facts remain. The need for wildlife damage management is now a necessity in many instances, and the discipline is experiencing geometric growth. The real challenge is to make the best possible choices despite the controversies, within the already developed fabric. This presentation focuses on the contributions that USDA Wildlife Services is making to these efforts.

Developing a management strategy to reduce roof rat, Rattus rattus, impacts on open-cup nesting songbirds in California riparian forests

In 2001, roof rats were identified as major predators of open-cup songbird nests in old growth riparian forests of California’s Central Valley. Nest predation was as high as 80%. For some bird species in recent years, the populations had declined, and their range was reduced. A management strategy to reduce rat impacts on songbirds was considered a priority. Following a review of the literature and consultation with land managers and experts in rodent management and bird conservation, we decided to reduce rat populations with poison baits delivered in bait stations immediately prior to the songbird nesting period. We subsequently conducted studies to provide information on rat home range and habitat use, potential baits, optimal bait station placement and distribution, and the potential non-target hazards of the program. The management strategy was then implemented in one riparian forest tract in October - December 2003. This is an adaptive management approach that will be evaluated in 2004, modified as necessary, and if successful, potentially applied to other riparian forests. In this paper we describe our approach to developing the management strategy, provide preliminary results, and discuss some of the potential problems with its implementation on a large scale.

Predator management for the protection of the endangered California least tern (Sterna antillarum brownii) and documentation of bullsnake (Pituophis catenifer) predation in San Diego County, California

The endangered California least tern is a seasonal migrant that nests in colonies on coastal estuaries and beaches of California. A variety of native and non-native predators prey on nesting terns and have the potential to devastate nesting colonies. USDA APHIS Wildlife Services (WS) conducts an annual program to reduce predation and protect nesting terns. Management activities include monitoring and removing known and potential predators with the selective use of various trapping and removal techniques. The most common predators managed at nesting colonies include feral cats, striped skunks, Virginia opossums, California ground squirrels, common ravens, western gulls, American kestrels, and barn owls. However, during the 2003 nesting season, WS documented the loss of 61 least tern nests due to predation by bullsnakes at a colony at North Fiesta Island in Mission Bay, San Diego County. This paper gives an overview of the WS predator management program for the protection of the endangered least tern and describes the nature and management of predation by bullsnakes.

The effects of raven removal on sage grouse nest success

We measured the effects of common raven removal on the nest success of greater sage grouse. One cause of sage grouse population decline is thought to be reduced nest success due to egg depredation by ravens. Ravens are nest predators that have substantially increased in abundance in response to current human land-use practices. In many areas, wildlife managers use egg baits treated with DRC-1339 to reduce raven numbers in sage grouse habitat. The effects of raven removal on grouse nest success and identification of any compensatory nest predators are largely unknown. During 2002 and 2003, USDA WS removed ravens from an experimental area in Nevada, within which we deployed miniature, camouflaged video cameras with time-lapsed recorders at sage grouse nests. Using continuous video monitoring throughout the incubation period, we determined the identity and observed the behavior of sage grouse nest predators. Sage grouse nest success during 2002 and 2003 was 74% (n = 19), with no depredations of sage grouse nests or sage grouse nest visitations by ravens. We also observed the behavior of animals that encountered nests, and we identified possible biases with estimating raven “take” from the attrition of egg baits. We found video cameras to be effective devises for identifying predators. These results may be useful in formulating future predator removal activities for sage grouse management.

Strategies for reducing feral cat threats to endangered Hawaiian birds

Introduced predators are one of the most important limiting factors for endemic Hawaiian forest birds. In the sub­alpine zone of Mauna Kea on the island of Hawaii, the primary predators of the endangered Hawaiian finch, palila (Loxioides bailleui), are feral house cats. Remote video monitoring revealed that feral cats are primarily diurnal predators of palila during the extended period of nestling development. Reducing this predation is necessary for population recovery and efforts to reintroduce palila to parts of their historical range. Currently, feral cats are removed with an extensive array of live traps. Since 1998, 7,344 trap nights of effort have been implemented, and although temporary declines in capture occur within seasons, cumulative capture rates show there has been little lasting effect from season to season. New emphases on improving capture efficiency include improved techniques for attracting cats to traps with lures that require infrequent refreshing or maintenance, “smart trap” technology that efficiently notifies managers when traps of all types contain animals, and adaptive strategies for managing feral cat populations in a variety of habitats and parks in the Pacific. Further documentation and interpretation of feral cat impacts on native wildlife will help prioritize and justify requests for increased funding for predator management. Accurate information on feral cat problems will help educate decision-makers and the public of the need for increased funding to protect endangered birds from this threat.

Potential flotation devices for aerial delivery of baits to brown treesnakes

Brown treesnakes are exotic invasive predators that have extirpated native forest birds and caused drastic reductions of lizards on Guam. Operational management control methods to contain the snake on Guam include the use of live traps, hand capture from fences, and canine detection. Live traps are also used to depopulate small forest plots. Toxicants offer an additional means for reducing snake populations on small plots. Polyvinyl chloride (PVC) plastic pipe bait stations containing dead neonatal mice (DNM) treated with 80 mg acetaminophen are placed about 1.5 m above the ground in vegetation to reduce exposure to terrestrial scavengers such as toads, crabs, and feral pigs. Live traps or bait stations are not practical to use in remote, large-scale areas of forest but aerial delivery of baits may have application. Small plastic parachutes have been used for entangling DNM in forest canopy but parachutes are relatively expensive and cumbersome to use. Inconveniences can be tolerated when only a small number are deployed. But it is anticipated that several thousand baits may be delivered per drop, and inconveniences must be kept to a minimum to maintain an efficient aerial drop system. We therefore evaluated 5 types of flotation materials dropped by helicopter, using DNM implanted with radio transmitters to record landing site (canopy or ground) and bait consumption by snakes and non-target animals. The types of material and percentage of baits that became entangled in the canopy were: paper ring – 39%, paper drinking cup – 50%, excelsior (wood shavings) and burlap – each 56%, and commercial paper food cup – 60%. For all devices, bait consumption by snakes ranged from 19-50% and bait consumption by non-target toads and crabs ranged from 0 - 11%. Commercial food cups were the most convenient material to use because they could be nested together prior to deployment.

The mongoose in the Caribbean: Past management and future challenges

In the late 1800s, the small Indian mongoose was introduced to the Caribbean islands in one of the most widespread purposeful introductions of a mammalian predator in history. Intended as a biological control agent for introduced rats in sugarcane plantations, the mongoose quickly became recognized as a pest due to its predation on poultry and native fauna, and injuries to livestock. Over the last 40 years, the mongoose has also emerged as the primary vector and reservoir for rabies on several Caribbean islands. Due to the estimated costs associated with this introduced carnivore, as well as potential ecological impacts, the mongoose is now listed as one of the top 100 worst invaders by the IUCN. Past large-scale control attempts in the Caribbean have proven unsuccessful, and few to none are currently being implemented. In fact, despite its renown, very little is known about the actual impacts of the mongoose. It is likely that combined with increasing rates of development in some Caribbean islands, the impact of the mongoose on native faunal communities may become more serious. This paper provides an overview of mongoose management in the Caribbean. Although current management priorities center on the role and management of the mongoose as a disease vector, this paper will also discuss opportunities to pair this research with 1) an assessment of the ecological impacts of the mongoose on native species, and 2) the development of mongoose control methods. The Caribbean National Forest, Puerto Rico is used as a case study; however, these methods can potentially apply to other Caribbean islands.

Actions speak louder than words: a call for preventing further mongoose invasions in Fiji

The small Indian mongoose was deliberately released into Fiji to control rats. Unfortunately, since their arrival many bird and reptile species have disappeared from the two largest islands, Viti Levu and Vanua Levu, and mongoose are the likely culprits. Fortunately, mongoose have not been introduced to every island in Fiji. Thus, it is imperative that we prevent mongoose from ever reaching these offshore havens. However, this is unlikely because the public is not aware of the problems created by mongoose and there are few biosecurity controls in place. To prevent further mongoose invasions, we need an active “first-strike” response team that will rapidly deal with any reported incursions. The various “first-strike” methods that should be employed to prevent mongoose from invading these mongoose-free Fijian islands are discussed.

Techniques and approaches for the removal of feral pigs from island and mainland ecosystems

Feral pigs cause considerable damage to island and mainland ecosystems around the world. Eradication efforts can be extremely challenging and may require many years. Some techniques used in removal programs include: trapping, hunting with dogs, ground hunting, aerial shooting, and fencing. Trapping can be very successful when pig densities are high and natural forage is at a minimum. Dogs can be used at any time, but are best used when pig densities are moderate to low, and during the cool wet months of the year. Ground hunting techniques are valuable throughout an entire eradication process because they can be used opportunistically with other techniques and often remove pigs less susceptible to other methods. Aerial shooting can be very effective in certain situations where the terrain permits easy location of animals from the air. Fencing, while expensive, can prove indispensable for pig eradication projects and can be used to contain a population, divide a population, or exclude animals from sensitive areas. The difficulty of performing a pig eradication project can be compounded by logistically challenging aspects of working on an island. However, islands have the distinct advantage of not requiring a perimeter fence, and upon completion, the island will remain pig-free unless pigs are intentionally reintroduced. Mainland pig eradication projects depend entirely on the integrity of a perimeter fence. Therefore, there is a constant threat of pigs becoming reestablished if the fence integrity is compromised. Thus, a perimeter fence must be vigilantly monitored during eradication and indefinitely afterward. A flexible plan with solid financial backing is necessary for any eradication project to be successful. Finally, safety is the number one concern when working in remote field locations and handling firearms.

Coyote attacks: an increasing suburban problem

Coyote attacks on humans and pets have increased within the past 5 years in California. We discuss documented occurrences of coyote aggression and attacks on people, using data from USDA Wildlife Services, the California Department of Fish & Game, and other sources. Forty-eight such attacks on children and adults were verified from 1998 through 2003, compared to 41 attacks during the period 1988 through 1997; most incidents occurred in Southern California near the suburban-wildland interface. Attack incidents are typically preceded by a sequence of increasingly bold coyote behaviors, including: nighttime coyote attacks on pets; sightings of coyotes in neighborhoods at night; sightings of coyotes in morning and evening; attacks on pets during daylight hours; attacks on pets on leashes and chasing of joggers and bicyclists; and finally, mid-day sightings of coyotes in and around children’s play areas. In suburban areas, coyotes can lose their fear of humans as a result of coming to rely on ample food resources including increased numbers of rabbits and rodents, household refuse, pet food, available water from ponds and landscape irrigation run-off, and even intentional feeding of coyotes by residents. The safe environment provided by a wildlife-loving general public, who rarely display aggression toward coyotes, is also thought to be a major contributing factor. The termination or reduction of predator management programs adjacent to some urban areas has also served to contribute to coyotes’ loss of fear of humans and to a dependency on resources in the suburban environment. Corrective action can be effective if implemented before coyote attacks on pets become common. However, if environmental modification and changes in human behavior toward coyotes are delayed, then removal of offending predators by traps or shooting is required in order to resolve the threat to human safety. We note the failure of various non-lethal harassment techniques to correct the problem in situations where coyotes have become habituated to human-provided food resources. Coyote attacks on humans in suburbia are preventable, but the long-term solution of this conflict requires public education, changes in residents’ behavior, and in some situations, the means to effectively remove individual offending animals.

Behavioral responses of coyotes to the CLOD in familiar and unfamiliar environments

The Coyote Lure Operative Device (CLOD) is designed to deliver a variety of substances to coyotes. Field evaluations have demonstrated free-ranging coyotes will activate CLODs, but little is known about coyote behavior when encountering the device in familiar or unfamiliar environments, an essential consideration. Captive coyotes show neophobic behaviors toward novel objects in familiar territory, while responses to scent stations in similar scenarios have been mixed. Free-ranging coyotes are more likely to investigate novel items and are more vulnerable to capture while trespassing in adjacent territories than when “at home”. We examined responses of captive coyotes toward CLODs in familiar and unfamiliar settings. We found no significant neophobic response toward CLODs with respect to territory familiarity, although captive coyotes spent significantly more time within 1 m of the device in a familiar environment. Relatively small sample sizes make broad inferences difficult, but our data suggest that territory familiarity might not be a strong factor in responses to the CLOD. However, more research is necessary.

Operational field evaluation of a plastic bulb reservoir as a tranquilizer trap device for delivering propiopromazine hydrochloride to feral dogs, coyotes, and gray wolves

We evaluated a polyethylene bulb reservoir fabricated at the Pocatello Supply Depot, Pocatello, Idaho, as a potential cost savings replacement for the McBride rubber device that is used as a tranquilizer trap device (TTD). The polyethylene devices, also called pipette TTDs, were formulated with 0.6 g of propiopromazine hydrochloride (PPZH) and 0.4 g of ascorbic acid, an antioxidant. The pipette bulb was secured to a 1.6 mm-diameter cable and the cable was attached to the trap jaw. TTD testing was conducted during routine operational control under an Investigational New Animal Drug application (INAD 9528) from the U.S. Food and Drug Administration. The targeted animals were feral dogs in Guam, coyotes in Utah and Idaho, and gray wolves in Minnesota. Various degrees of tranquilization, ranging from quietness and lack of attention to sleepiness, were observed in the animals. Percent of tranquilization effects observed in feral dogs, coyotes, and wolves were 67%, 90%, and 67%, respectively. Evidence of reduced struggling and reduced injuries to feet and legs was observed. Tranquilization effects were also observed in non-target animals such as badgers, skunks, and raccoons. A mortality that was probably related to heat stress was recorded in one juvenile wolf. A major drawback of the pipette TTD was leakage at the stem attached to the trap jaw. Degradation of PPZH was also observed but was reduced compared to formulations without ascorbic acid.

Development of the West Virginia integrated predation management program to protect livestock

The West Virginia Integrated Predation Management Program was created in 1996 due to increasing livestock losses to coyotes and the inability of producers to solve the problem themselves. The eastern coyote arrived in West Virginia in the early to mid-1980s. By the early 1990s, coyote depredations were recognized as a serious threat to West Virginia’s livestock industries. At a June 26, 1995 public meeting in Riverton, West Virginia, livestock producers expressed to their state delegates and senators their concerns and frustrations with their inability to control coyote predation on sheep. This meeting provided the impetus for the creation of the West Virginia Integrated Predation Management Program as carried out by USDA APHIS Wildlife Services (WS). Wildlife Services predator management specialists in West Virginia integrate and apply or assist the producer in applying a combination of non-lethal and lethal alternatives to minimize coyote predation on sheep, goats, and calves. Wildlife Services has provided predation control workshops, on-site recommendations, and a guard dog cost-share program to encourage producers to implement non-lethal methods on their farms. Lethal control strategies directed at depredating coyotes have been either preventive or corrective. Preventive control has been initiated by WS prior to the onset of actual depredations in areas where historic losses due to coyote depredation have been documented and where there has been an imminent threat of loss of livestock. Corrective control by WS was directed at depredating coyotes in response to ongoing losses with the goal of removing the offending coyotes(s). In this paper, we discuss the development and success of the West Virginia Integrated Predation Management Program to protect livestock.

Weight and age of coyotes captured in Virginia, USA

We recorded the weight and age of 70 coyotes collected during depredation control efforts in western Virginia. Mean masses for adult male and female coyotes were 16.2 and 13.4 kg, respectively. Juvenile male and female coyotes weighed 14.0 and 13.0 kg, respectively. Regardless of sex, mean mass was greatest between November and January and comparable to that reported for coyotes throughout the eastern United States. Cementum aging indicated that 71% of the coyotes captured were greater than 1 year of age. Numerical trends suggest that age and sex may influence vulnerability to capture.

Evaluation of different rice baits and chemicals to improve efficacy of 2% DRC-1339 to reduce blackbird damage to rice

Blackbird damage to sprouting rice can be locally severe and costs Louisiana growers an estimated $4 million/year and Texas growers $4.4 million/year. DRC-1339 blackbird baiting programs probably will continue until available alternative control techniques (i.e., repellents) become available. We conducted 3 studies to evaluate different rice baits and chemicals to improve efficacy of DRC-1339 for use at staging areas. During the first study, individually caged red-winged blackbirds preferred untreated medium grain brown rice over long grain brown rice, rough rice, or rough rice soaked with sodium bisulfite. Of birds offered only medium (control), long, rough, and rough rice soaked with sodium bisulfite treated with 2% DRC-1339 diluted 1:25 with untreated carrier (medium, long, or rough rice), 90 to 100% died within 48 hrs. During the second study, individually caged red-winged blackbirds preferred untreated rice over rice treated with Harvest Guard or ethyl cellulose. Birds were offered only medium brown rice (control), Harvest Guard, or ethyl cellulose-treated medium brown rice treated with 2% DRC-1339 diluted 1:25 with untreated medium grain brown rice. With the medium grain brown rice (field bait), 100% mortality was observed within 48 hrs. With the Harvest Guard and ethyl cellulose treatments, ≤80% mortality was observed. The third study was an aviary test to determine if aging the chemical baits (sodium bisulfite, Harvest Guard, ethyl cellulose) for 3 days in Louisiana would affect mortality. Mortality with the fresh field and sodium bisulfite baits were 100%. We did not achieve ≥80% mortality with either the fresh Harvest Guard or ethyl cellulose bait. Mortality with the aged sodium bisulfite bait was 50%. None of the other aged baits produced >10% mortality. Degradation occurred with all the aged baits but occurred the least with the sodium bisulfite treatment. Future research will look at possibly combining sodium bisulfite with UV protectors to further reduce the degradation of DRC-1339 in the field.

Using Geographic Information System (GIS) software to predict blackbird roosting locations in North Dakota

Cattail stands provide roosting and staging areas for large congregations of blackbirds in North Dakota in late summer and early fall. Since 1991, the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services (WS) program has conducted a cattail management program in North Dakota to alleviate blackbird damage to ripening sunflower. To extend the capabilities of the program, a geographical information system (GIS) will be incorporated to help WS personnel find blackbird roosts more effectively. We will use the GIS to construct field maps showing the association between areas of moderate to high sunflower damage (>5%) and cattail-dominated wetland basins >2 ha. Buffer distances comparable to the distances blackbirds typically travel to forage will be placed around sunflower planting areas susceptible to high damage. This will help WS personnel focus their efforts on locating cattail-dominated wetlands that should be enrolled in the management program and improving current and future blackbird damage management programs.

Using Fatty Acid Profiles to Assess Dietary Intake of Sunflower in Red-winged Blackbirds

In late summer, red-winged blackbirds forage heavily on ripening sunflower crops in the Dakotas. Sunflower achenes have a distinct fatty acid profile that should influence the fatty acid composition in tissues of these birds. To determine if fatty acid composition in tissue could be used as a biomarker indicating dietary history, we fed 18 red-winged blackbirds a sunflower diet for 2 weeks and compared fatty acid profiles in their muscle and liver tissues to a control group of red-winged blackbirds (n = 15) fed a birdseed mix supplemented with safflower seed. Three subjects from each treatment group were sacrificed at Day 0, 7, 14, and 21, with Day 0 the day the treated group was switched to sunflower. The remaining birds were sacrificed on Day 35. Breast muscle and liver tissue were collected, extracted, and analyzed for levels of linoleic, oleic, palmitic, and stearic acids. Differences existed in levels of all 4 fatty acids between treatment groups pooled across time (P ≤ 0.05, ANOVA). When comparing fatty acid profiles between treated and controls by day sacrificed, we observed differences in levels of ≥1 of the fatty acids at Day 7, 14, and 21 in breast muscle, and Day 7 and 14 in liver tissue (P ≤ 0.05, t-test). Within-bird comparisons of fatty acid levels in liver and breast indicated temporal lags in metabolism between tissue types (P ≤ 0.05, paired t-test). Our results demonstrated that fatty acids profiles in body tissues can be used as biomarkers to verify recent foraging in sunflower by red-winged blackbirds.

What can birds hear?

For birds, hearing is second in importance only to vision for monitoring the world around them. Avian hearing is most sensitive to sounds from about 1 to 4 kHz, although they can hear higher and lower frequencies. No species of bird has shown sensitivity to ultrasonic frequencies (>20 kHz). Sensitivity to frequencies below 20 Hz (infrasound) has not received much attention; however, pigeons and a few other species have shown behavioral and physiological responses to these low frequencies. In general, frequency discrimination in birds is only about one-half or one-third as good it is for humans within the 1 - 4 kHz range. A problem that birds suffer that is similar to humans is damage to the auditory receptors (hair cells) from loud noises. The sound intensity that produces damage and the amount of damage produced differs depending on the species. Birds residing in the active areas of airports might be constantly subjected to sound pressure levels that damage their hearing. Thus, to effectively disperse birds using sound, auditory alerts must be at frequencies that can be detected by the damaged auditory receptors. Although some if not all species of birds have the ability to repair damaged hair cells, continued exposure to loud noises would prevent recovery of their hearing. In this paper I review what is known about avian hearing and compare that to the operational characteristics (frequencies, intensities, duration) of techniques and devices to disperse birds.

Capturing problematic urban Canada geese in Reno, Nevada: Goose roundups vs. use of alpha-chloralose

Urban Canada geese, in large numbers, have exploited human manipulation of the Reno, Nevada cityscape, creating human health and safety concerns along with monetary losses to businesses and private citizens. A primary concern from the start has been the potential for an aircraft-bird strike at the Reno-Tahoe International Airport. To address this urban goose problem, USDA APHIS Wildlife Services (WS) “rounds up” the problem geese by use of a funnel trap, where a gathering cage is placed at the junction of two plastic fence wings. Goose roundups occur on golf courses, city parks, and private residences. The use of the traps can be labor intensive on some properties, often requiring the coordination of federal, state, and city employees in addition to volunteers, to assure adequate personnel are available. A goose roundup is generally a high-profile public affair. WS makes every effort to start roundups early in the morning (4:00-4:30 A.M.) to avoid crowds, and more importantly, to reduce heat stress to the geese. However, there always seem to be a few citizens observing the operation. For many people, the sight of 20 to 30 geese enclosed in a small cage, honking and hissing, and potentially trampling goslings under foot, can be quite upsetting. Many urbanites only encounter Canada geese at the city park, where they typically enjoy feeding the local population. This limited exposure often results in negative reactions to goose capture and relocation efforts. To reduce the need for high-profile roundups in urban areas, WS experimented with the use of alpha-chloralose (AC) on urban geese located in select parks and gated communities. Alpha-chloralose is an avian tranquilizer that is administered orally to waterfowl through corn or bread bait. We hoped that the use of AC would change public opinion about the stress the geese might suffer during capture efforts. Further, we sought to capture repeat offending geese that had become wise to the funnel trap and avoided capture by that method. Since many properties are not suitable for funnel trap use, we wished to expand the WS urban goose management effort by employing this additional capture method. AC delivery by bread baits allowed for the precise targeting of problem geese. The advantages and disadvantages of both roundups and AC treatments are discussed.

Capturing nuisance urban Canada geese using the bird immobilizing agent alpha-chloralose in Reno, Nevada: What we learned

This paper discusses several challenges Wildlife Services (WS) personnel encountered while conducting alpha-chloralose (AC) treatments on Canada geese in Reno, Nevada during May and June 2003. While the WS AC training manual provides guidelines for the safe and effective anesthetization of Canada geese using this chemical immobilization tool, we encountered and solved problems and challenges that had not been reported in previous reports on projects using AC. Problems we encountered ranged from being accosted by drunks to interrogations by “elderly ladies” worried that we might be taking their favorite goose. Challenges in collecting immobilized geese resulted from river currents and their effect on AC-treated geese, moss entangling the boat motor propeller on ponds, and automatic sprinklers turning on at inopportune times. It is hoped that addressing these real-world experiences can help others become more proficient in AC field use.

Response of Canada geese to a dead goose effigy

The North American Canada goose population increased at a rate of 10.5% per year, 1966 - 2001. Canada geese rank as the third most hazardous species in regards to collisions with aircraft. Sound Canada goose management tools are critical for a safer airport environment. We conducted field evaluations of a Canada goose effigy during the breeding season with territorial pairs and in late summer with post-fledging flocks to determine if geese were deterred by the effigy. No difference in territorial pairs was found between pretreatment and treatment periods for Canada geese when goose effigies were placed within their territories. In post-fledging flocks, the mean number of geese observed during pretreatment (74.9 ± 12.9), treatment (14.8 ± 4.5), and posttreatment (53.6 ± 14.2) periods differed (P < 0.01). There was no difference (P = 0.56) between the mean number of geese observed during a second round of 5-day pretreatment (58.7) and 5-day second round treatment (43.7) periods. By itself, the goose effigy was not effective as a Canada goose deterrent after approximately 5 days. However, this effigy may have some potential in an integrated goose control program conducted outside of the breeding season. Further evaluation of the effigy as part of an integrated Canada goose control program is recommended.

Resolving urban Canada goose problems in Puget Sound, Washington: A coalition-based approach

Recent decades have seen dramatic increases in resident populations of urban western Canada geese throughout the United States, including locations in the Puget Sound in western Washington. By 1987, populations of urban Canada geese grew to problematic levels in the greater Seattle area, and caused such extensive damage that the Seattle Metropolitan Area Waterfowl Management Committee (Seattle Metropolitan WMC) was formed. The Seattle Metropolitan WMC was comprised of 15 representatives from cities and jurisdictions in the greater area, the U.S. Department of Agriculture Wildlife Services, and the University of Washington. The Seattle Metropolitan WMC worked with state and federal wildlife agencies, advocate groups, and the public to identify their concerns, determine the extent of the problem, and formulate management options. Non-lethal management options, including relocation, were implemented in 1989. Egg-oiling was initiated in 1993. Relocation efforts were phased out after 1995, and the first substantial lethal removal was begun in 2000. Other management actions taken by the Seattle Metropolitan WMC included harassment, exclusion, repellents, habitat modifications, and public education. In 1998, escalating urban Canada goose problems in another area of Puget Sound precipitated the formation of a second committee, south of Seattle, involving Thurston County and the cities of Olympia, Lacey, and Tumwater. Using a slightly different approach than the Seattle Metropolitan WMC, management officials opted to hold a public meeting to solicit input and participation from individuals, groups, and agencies. Attendees were encouraged to serve on a steering committee which, when formed, included city and county officials, park managers, state and federal wildlife biologists, hunters, advocate groups, and citizens. Over the next 18 months, the committee identified problem areas, considered public concerns, reviewed management options, and utilized volunteers to count geese. From these efforts, a Resident Canada Goose Management Plan was developed. The plan, which was implemented in 2000, identified population and program objectives utilizing a full range of management options. The Seattle and Thurston County programs each were successful in reducing urban Canada goose problems. In Thurston County, a fully integrated approach including population reduction through lethal control was implemented in the first year. An immediate reduction in goose problems was evident, and the plan objectives were achieved within 4 years. In the Seattle area, goose damage problems were not substantially reduced until after the implementation of lethal removal in 2000. By 2003, the fourth season involving lethal removal, the number of urban geese and their associated damage had been reduced by approximately 60%. In both locations, the need for lethal removal declined during successive years of the program. Animal rights groups were vocal and took action to prevent lethal removal, but public demands for removal grew during the late 1990s as goose problems worsened. Although controversial at first, public and media support grew as facts came to light and Canada goose conflicts were reduced.

Protecting Canada geese on a wildlife management area in east-central Nevada

In early 2003, at the request of the Nevada Department of Wildlife (NDOW), Wildlife Services (WS) conducted wildlife damage management (WDM) activities to protect nesting waterfowl within the Key Pitman Wildlife Management Area (KPWMA) in east-central Nevada. The WDM activities were aimed primarily at protecting Canada geese from predators, primarily coyotes and common ravens. The KPWMA (approximately 2,000 hectares) provides important habitat for the nesting and rearing of Canada geese in a predominantly desert area. Although the KPWMA’s habitat has been judged by biologists to be adequate for successful waterfowl nesting, the number of gosling geese hatching and surviving to flight stage in recent years has been considered by NDOW biologists to be unacceptably low. Predatory mammalian and avian species seen concentrated around water areas of the WMA were believed to be a primary factor in the low survivability. WS was contracted by NDOW to conduct WDM activities during the period of the goslings’ greatest vulnerability to predation, March through June. As per directions from NDOW, WDM activities targeted only coyotes and common ravens found within, or immediately adjoining, waterfowl nesting areas. A significant increase in the number of goslings surviving to flight stage was set as the measure of whether the project was a success. WS used DRC-1339-treated chicken eggs placed in close proximity to waterfowl nesting areas to reduce raven numbers at these specific sites. To remove offending coyotes, WS utilized leghold traps, trail snares, and calling and shooting. NDOW reported a significant increase in Canada goose goslings surviving to flight stage following the 4-month treatment period, and deemed the project a success.

Trends in North American vulture populations

In recent years, interactions between vultures and human activities have noticeably increased. These interactions include nuisance roosts, damage to homes and businesses, livestock depredation, and collisions with aircraft. One major factor contributing to the upsurge in vulture problems is higher numbers of these birds. Both turkey vultures and black vultures appear to be experiencing major population increases throughout much of their ranges in the United States. During 1990-2002, Christmas Bird Count (CBC) data revealed annual nationwide increases of 1.79% and 5.97% for turkey vultures and black vultures, respectively. Estimates from Breeding Bird Survey (BBS) data were 1.99% and 4.97% for the two species. Despite substantial differences in methodology associated with these two sets of data, they are consistent in charting overall increases in populations of both vulture species. Positive population trends are mostly confined to the eastern half of the country. The usefulness of survey data like the CBC and BBS is currently being seriously questioned, but for vultures I contend that the objections to the survey data are not critical. Nevertheless, suggestions for improved data collection procedures are offered.

Vulture-cattle interactions at a central Florida ranch

Black vulture depredations to newborn livestock, poultry, and other captive animals have been reported from at least 15 states, and during the 1990s, reports of depredations increased annually by an average of 18%. In response to this issue, we initiated a study at Buck Island Ranch of the MacArthur Agro-Ecology Research Center in central Florida to examine interactions between cattle and vultures. Based on previous reports, we hypothesized that vulture predation selectively targets calves of young, inexperienced cows. To document vulture activity, we conducted point counts of vultures in pastures throughout the ranch from January 2000 to March 2001. During point counts, turkey vultures accounted for 78% of the observations compared to 22% for black vultures. We noted that vultures used certain pastures preferentially, with over 70% of the vultures in 3 pastures where heifers were calving and the remainder spread among 7 pastures containing yearling heifers only or cows and calves. Turkey and black vultures were often present during the 19 calving events we observed, but usually neither species exhibited threatening behavior toward calves or calving heifers. Instead, the birds seemed intent on gaining access to the afterbirth. On one occasion, however, we observed an attempted depredation by black vultures on a calf as it was being born. The cow was able to chase the birds off, however, and the birth proceeded successfully. We conclude that predation by black vultures occurs when the birds identify and then exploit vulnerable animals, although there is still much to be learned regarding the circumstances that promote such activity. Current management recommendations include dispersing nearby black vulture roosts and providing careful oversight to protect inexperienced cows that are first-time breeders.

Evaluation of trapping to reduce monk parakeet populations at electric utility facilities

Through accidental and intentional introductions, the monk parakeet, native to South America, is now established in several parts of the United States. In Florida, it occurs in 21 of 67 counties. Monk parakeets build a bulky nest structure of sticks, and they often build on electric utility substations and support structures for distribution and transmission lines. This nesting activity is incompatible with reliable electric service because nest material creates short circuits that cause power outages. Nest removal by electric utility personnel is ongoing but provides only short-term relief, as birds readily rebuild their nests. In this study, we evaluated passive and active methods to trap monk parakeets, and we documented the effectiveness of trapping to reduce rates of nest rebuilding on distribution poles. At electric substations, we tested two passive trap designs: a drop-in style trap, and a walk-in style trap. Monk parakeets were wary of traps, however, and were not easily captured even with extensive pre-baiting and the use of decoy birds. At distribution poles, we actively trapped birds at 47 nest sites using specially designed nets placed over nest entrances at night while birds roosted. Birds were then caught as they flew out of the nests into the net. Capture success at individual nest sites ranged from 0 to 100% with an overall average of 51%. Of the 47 sites where birds were trapped at night, 43 nests were removed immediately or shortly after netting. Subsequent monitoring revealed that higher nest site capture rates resulted in slower rates of nest rebuilding. We conclude that while more research is needed to design an effective passive trapping system, monk parakeets can be readily trapped from distribution pole nests at night thereby enhancing nest removal efforts.

Electronic repeller and field protocol for control of crows in almonds in California

Past studies have shown that the American crow, a major pest in almonds, can be effectively hazed out of almond orchards with broadcast distress calls. These studies, however, have not approached the matter from an integrated pest management standpoint. A large-scale field protocol was required to guide growers when using electronic broadcast units. A broadcast unit was designed for testing the field protocol with emphasis placed on preventing habituation and saving power. A selection of crow chick distress calls were recorded on the University of California-Davis campus for use in the broadcast unit. In addition, recordings of 2 dying adult crows were obtained from the United States Department of Agriculture National Wildlife Research Center in Fort Collins, CO. The calls proved effective in preliminary hazing tests and during the field study. The field protocol included broadcast unit deployment at the first sign of bird damage at a rate of one unit per 1.6 ha, distributed uniformly throughout the orchard, moved to a new tree every 2 weeks, and automatically switched to a different call every 3 to 4 days. Growers at each site were also supplied with pyrotechnics to supplement the distress calls and were encouraged to use other techniques such as shooting and gas cannons. The units ran until harvest. Six orchards, a pair from each of 3 different areas in California, were chosen to test the field protocol. The orchards were surveyed for damage over 2 growing seasons, and 1 orchard in each pair received treatment in the second year. Two of the 3 treated sites showed a decrease in damage due to the treatment of the broadcast units implemented with the field protocol. One site showed a damage reduction from 0.84 (6.0 kg/ha) to 0.25 (1.1 kg/ha). Another site showed a damage reduction from 1.54 (18.2 kg/ha) to 0.73 (4.8 kg/ha). The third site was not damaged in the first year, therefore damage reduction in the second year was not possible.

Bird depredations in Uruguayan vineyards

Many species of birds in Uruguay frequent vineyards and damage grapes, both species that are considered crop pests and species that are protected by law because their conservation and protection are desirable. We surveyed 70 farmers in the Department of Canalones, the main grape growing region in Uruguay, to determine their perceptions about the nature and severity of bird depredations and the methods being employed to reduce such damage. Sixty-seven percent of respondents reported receiving damage from birds. Bird depredations were considered a serious problem by 58% of respondents, a moderate problem by 19% of respondents, and a minor problem by 19% of respondents. The species most often cited as causing damage were Picazuro pigeons, great kiscadees, and creamy-bellied thrushes. Respondents use a variety of methods to deter bird depredations including firearms, toxic baits, visual deterrents, and chemical repellents. We describe a research proposal to determine more precisely the magnitude of bird depredations in Uruguayan vineyards, to adapt and/or develop management tools, and to formulate and implement a pilot management plan for reducing bird depredations.

Investigations of commensal rodenticide baits against wild Norway rats plus additional toxicology data of warfarin on laboratory Norway rats and house mice

The use of warfarin in commensal rodenticides has been avoided by the pest control industry for many years because of concerns with low palatability, resistance, and its chronic toxicity requirements. It has been all but forgotten by the industry. Genesis Laboratories, Inc. evaluated warfarin in a currently-marketed commensal rodenticide, Kaput Rat and Mouse Bait (0.025% warfarin), in comparison to Maki pellets (0.005% bromadiolone) and Talon G pellets (0.005% brodifacoum) in a simulated field study design using warfarin-resistant wild Norway rats. Approximately 20 wild rats of varying ages and weights were randomly added to each of 3 study rooms, one for each product. After a 7-day acclimation period, the respective rodenticide baits were presented to the rats along with the EPA field rodent challenge diet or another alternate diet. The first death in each study room was recorded on Day 3 for Kaput, Day 13 for Maki, and Day 5 for Talon. Kaput acceptance was high, causing 9 deaths in the first 14 days. Again, because of poor acceptance of the Maki and Talon baits, the alternate diet was changed to milo on Day 22 and again to a no-choice regime on Day 28. At this point (Day 28), efficacy of the Kaput, Maki, and Talon rooms were at 85%, 20%, and 10%, respectively. 100% efficacy was achieved on Day 36 by Kaput, Day 38 by Maki, and Day 42 by Talon during the no-choice phase of the study. To investigate the warfarin toxicology profile further, we initiated another study with laboratory Norway rats and house mice in a no-choice regime with varying exposure periods (1, 2, 3, 4, and 5 days). At least two days of exposure was required to produce 100% mortality with the rats and 5 days of exposure was necessary for 100% mortality of house mice.

Montane vole control with Rozol® paraffinized pellets in orchards of the Pacific Northwest

Rozol® Paraffinized Pellets (0.005% chlorophacinone) were effective in reducing populations of montane voles greater than the EPA standard of 70%. This test substance was applied using a Vicon spreader at the approximate rate of 10 lbs/acre to the vegetation of the orchard floor. An intensive mark-recapture census was used as a direct census to determine population change as a result of the test substance application. An apple slice index was used as an indirect method to confirm population change. Few carcasses were found during the carcass search practiced in this study. Determination of active ingredient residues was done on the vole carcasses found during the carcass search events.

Assessing potential for using zinc phosphide bait to control nutria on Louisiana coastal marsh

Nutria are large semi-aquatic rodents native to South America. Nutria were first introduced to the United States because of their fur, and some populations remain economically important to the fur industry. Accidental and intentional releases have permitted them to establish in wetlands across the United States. Burrowing and foraging by nutria often inflict severe damage and can be devastating to native vegetation. Nutria are recognized as at least a contributing factor to the decline of native Louisiana coastal marsh. Management plans to reduce impacts require reducing nutria populations, or where possible, eliminating them from target sites. At present, public hunting and trapping encouraged by an incentive payment program are primary approaches to reduce unwanted populations. However, alternative tools, including toxins, need to be assessed for possible use. Previous studies assessing zinc phosphide baiting have addressed nutria control on open waterways. Considerable data can be extrapolated from these prior studies and applied to baiting on coastal marshes. However, animals may respond differently to baits and baiting strategies applied to coastal marsh. We conducted a series of studies to assess the potential for developing a feasible strategy to suppress nutria populations with zinc phosphide bait on Louisiana coastal marsh. Tetracycline and metallic flakes show promise as tools for studying nutria foraging behavior. Nutria activity on rafts was marginal, probably because of their access to native vegetation. Simple audio, olfactory, and ocular cues tested as attractants to entice nutria to bait station showed marginal efficacy. Olfactory stimuli demonstrated the most potential for developing future attractants.

Assessing the efficacy of chlorophacinone for mountain beaver (Aplodontia rufa) control

The mountain beaver is a fossorial rodent species endemic to the Pacific Northwest and portions of California. This herbivore is managed as a pest species because of the impact it has on newly planted Douglas-fir seedlings. Currently, managers are limited to trapping for population control; however, in Washington trapping has been further curtailed by anti-trapping legislation. Presently there are no registered underground toxicants for mountain beaver control. We have documented the efficacy of chlorophacinone, presented in daily doses, as a possible alternative for mountain beaver control. Daily baiting would be unreasonable and costly alternative for timber managers, so we conducted a series of tests to determine if a single or double baiting was efficacious. In addition, we tested the caching behavior of the mountain beaver when offered bags of oats. This behavior may help reduce impacts to non-target species as well reduce environmental exposure and degradation. Mountain beaver readily cached bags of chlorophacinone within their artificial burrows, and efficacy of a one-time and two-time dose was 100%. We determined that even with the highest chlorophacinone residuals (0.354 ppm) that the risk quotient for mink and red-tailed hawk was exactly at the level of concern that EPA recognizes for endangered and threatened species.

The effects of lactation on seedling damage by mountain beaver

The mountain beaver is a semi-fossorial rodent of the Pacific Northwest and is among a variety of herbivores that retard plant growth and cause tree seedling deformities and mortality. Douglas-fir seedlings are planted in the Pacific Northwest from February through March, a period coinciding with mountain beaver parturition. Previous research suggested that in spring, lactating females depend more on conifers than do non-lactating females and males. We conducted experiments to determine if female reproductive condition influenced seedling damage, and if physiological stage of the seedling affected damage. Dormant and flushing trees were offered to 6 pregnant and 6 non-pregnant females in 2002 and 2003. We found no difference between female condition and damage in 2002, but there was a significant difference between type of tree and damage (F6,79 = 6.75, P < 0.001). In 2003, we found a difference in seedling damage (F3,95 = 16.41, P < 0.001), with tree type (P < 0.001) and female condition (P = 0.02) contributing to the model. More flushing trees were damaged in both years than dormant trees, once bud break occurred. Statistical analyses of fructose (F5,23 = 12.07, P < 0.001) and glucose (F5,23 = 12.86, P < 0.001) concentration data indicate that tree type (dormant or flushing) was a significant effect (P < 0.001). The interaction between tree type and week sampled was also significant in both the glucose (P = 0.002) and fructose response (P = 0.009). Both fructose and glucose concentrations were the lowest in new flushing trees, and mountain beaver did not appear to be selecting flushing trees for their needle sugar content. Water concentration also varied between tree type but was not affected by the sampling time (F5,20 = 35.46, P < 0.001). New and dormant growth tissues had similar water concentrations that were greater than old growth tissue. Mountain beaver are dependent upon a constant water source, although it does not appear that damage is related to water availability. Further analyses of terpene levels and stem carbohydrate levels are needed before conclusions on mountain beaver selectivity can be reached.

Assessment and monitoring of California vole (Microtus californicus) feeding damage to a coastal redwood (Sequoia sempervirens) restoration project

Throughout its range, coast redwood is subjected to vertebrate feeding damage at various life stages. Although some quantified information exists regarding feeding behavior by black bears and woodrats, only anecdotal evidence exists for most rodent feeding behavior, including California voles. This project adds to the base of knowledge regarding vole damage to sapling coast redwoods by describing and quantifying damage characteristics, and it establishes a protocol for field assessment and monitoring over time. It describes the distribution of vole feeding damage within a sample area, and it identifies cultural practices that potentially intensify feeding behaviors. An index is developed and provided to assay damage to saplings, in order to facilitate field assessments. A monitoring scheme is presented to evaluate sapling vigor and growth over time. Additionally, pruning of saplings is being assessed to evaluate the utility of this treatment in improving growth traits to damaged trees.

The possible effects of bait container design on mouse feeding activity in real-world structural baiting situations

Tamper-resistant rodenticide bait containers are used extensively around the world for a multitude of rodent pest management efforts. A large portion of their use, however, is for protecting industrial food and pharmaceutical plants from commensal rodent invasions. Yet, no research exists as to the possible effects of bait container “architecture” on the feeding activity of the targeted rodents. This study compared two common, yet architecturally different, tamper-resistant bait containers for feeding and general activity as measured by deposited feces and feeding consumption on installed rodenticide bait blocks. The study, primarily involving house mice, was conducted over a 17-week period in a real-world baiting situation along the exterior perimeter of an industrial grain processing plant. The low-profile bait container, as represented by the Multiplex™ brand, exhibited a 17.8% greater amount of fecal pellets and a 15.4% heavier feeding index compared to a high-profile container, as represented by the Bell Laboratories Protecta container.

West Nile virus: Impact on crow populations in the United States

Since the introduction of the mosquito-borne West Nile Virus (WNV) into New York City (NYC) in 1999, it has expanded westward across the North American continent in an unprecedented fashion, taking in its wake hundreds of thousands and possibly millions of native and exotic birds. Corvid species, particularly the American crow, are particularly susceptible to this virulent strain of virus and have died dramatically during the summer virus transmission season. Experimental studies have shown that the fatality rate from WNV infection in American crows is nearly 100%. This mortality in crows and other corvids was used as a sensitive sentinel system to detect the presence and movement of the virus through a public reporting and laboratory testing national surveillance program. Crows were also the earliest indicator of virus activity in the majority of locations and were a useful predictor of human cases. Bird mortality from WNV peaks during August-September at the height of the mosquito-transmission period but extends from April to November each year in some states. An impact of WNV on local populations of crows was observed in some localities such as the NYC area, but no significant declines have been detected yet by the regional population trend data. The geographical distribution of WNV activity is not continuous across local landscapes and unexposed crows can then serve as a source to repopulate affected areas when overall populations are high. If WNV transmission continues for years with regular mortality, the resiliency of the regional crow populations to sustain this high mortality rate will diminish.

Relative factor costs of wildlife rabies impacts in the U.S.

A comprehensive cost model of wildlife rabies is presented. A total of 11 factors were viewed to comprise the diverse agricultural, insurance, medical, and veterinary expenses associated with rabies (i.e., pet vaccinations, livestock vaccinations, pet replacements, livestock replacements, pre-exposure prophylaxis for humans, post-exposure prophylaxis for humans, adverse medical reactions, animal control activities, public health charges, quarantine costs, and human death settlements). These factor costs form the basis of potential savings to be gained from rabies control activities. Irrespective of incidence, per unit costs and ranges were found to be greatest for livestock replacement, post-exposure prophylaxis, adverse medical reactions, and human death settlements, with substantial costs of adverse medical reactions and human deaths occurring infrequently but due to potential insurance or litigation claims. Empirical studies are needed to document the incidence of these factors during pre-epizootic, epizootic, and post-epizootic phases of wildlife rabies.

Oral rabies vaccine (ORV) bait uptake by striped skunks: Preliminary results

Aerial delivery of rabies vaccine-laden bait is effective and efficient for large-scale vaccination of wildlife. Oral rabies vaccine (ORV) contained in a sachet (or blister pack) inside baits that serve as the mode of delivery currently are used for orally immunizing foxes, raccoons, and coyotes. The technique remains in the vaccine-development stage for oral immunization of skunks. Since skunks are a major vector of the rabies virus, concurrent development of a bait that is sufficiently attractive to skunks would facilitate an immediate mode of delivery once a vaccine is developed. We ran a palatability experiment with different shapes and flavors of baits to assess uptake by captive skunks. The flavors most preferred were fish and chicken. We also evaluated the fate of the sachet (punctured or not) inside baits, which would assist in assessing the delivery of a vaccine dose. On average, cylindrical-shaped baits had a higher percentage of punctured sachets than did rectangular-shaped baits, and baits with their matrix directly coated onto the sachet had a higher percentage of punctured sachets than did those baits in which the sachet was “held.” We also used sulfadimethoxine, a short-term quantifiable biomarker, as a mock vaccine inside sachets in an attempt to quantify the amount of liquid ingested by skunks after consuming baits of different shape and size. While this information could have been useful for assessing the amount of vaccine delivered via sachet puncture, it could not be determined due to an aversive tasting biomarker. For effective ORV bait uptake by skunks, modifications to current baits should include a smaller size and a meat flavor matrix that is directly coated onto the sachet.

The role of bait manipulation in the delivery of oral rabies vaccine to skunks

The majority of rabies cases reported to the Centers for Disease Control each year occur in wildlife including skunks, raccoons, bats, foxes, and coyotes. Currently, oral rabies vaccination campaigns are employed to immunize coyotes, foxes, and raccoons. Though skunks are vectors of 6 rabies strains, there is currently no effective oral vaccine or delivery system for skunks. More information is needed to determine if baits currently used are sufficiently attractive to skunks, or if the baits are difficult for skunks to handle and consume. We observed bait manipulation by skunks in penned feeding trials to determine the bait type most conducive to ingestion and delivery of a mock vaccine to skunks. Smaller baits were easier for skunks to manipulate and consume, and vaccine containers coated with bait facilitated sachet puncture and increased the potential for vaccine delivery. Our information will be useful in the development of baits and vaccine containers for large-scale rabies vaccination campaigns that target skunks.

Passive tracking stations as a method for providing rabies reservoir population information for oral rabies vaccination

Knowledge of wildlife population abundance and activity patterns is integral to sound management decisions. Traditional methods of determining population abundance include mark-recapture, catch/unit effort, aerial and ground counts, and harvest-based or removal efforts. Capture methods are labor intensive and expensive. Census methods are potentially expensive and are often impractical for many wildlife species. Harvest-derived population estimates are not useful where harvest is limited. Tracking or scent stations have been used to index wildlife activity and abundance, but the use of traditional scented-tracking stations may lead to biased population activity or abundance estimates. We built on previous evaluations of passive and scented tracking stations to determine their potential utility for providing raccoon and other carnivore population information to support decisions for wildlife rabies control in coastal pine-oak communities. Methods were evaluated through several small-scale studies conducted in southeastern Massachusetts. Passive tracking stations appear more sensitive to raccoon activity than scented tracking stations (1.38% of scented stations visited vs. 3.38% of passive stations) under apparently low raccoon population densities. Despite concerns over the utility of track-based indices, we recommend the use of passive tracking stations to index raccoon activity over scented tracking stations.

Bovine tuberculosis in Michigan: The work on the wildlife side

In 1975 and again in 1994, bovine tuberculosis (TB) was diagnosed in a free-ranging white-tailed deer taken by a hunter in the Michigan’s Northeast Lower Peninsula. In subsequent testing of deer, it was clear that deer were not spillover hosts but, in fact, the infection was being sustained in the deer population. While bovine TB had been detected elsewhere in wildlife, this was the first time in North America that bovine tuberculosis was shown to be sustained in wildlife. While TB had no discernible effect on deer populations, it apparently provided a reservoir of infection to cattle. In 1998, TB was detected in cattle herds, which eventually prompted the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) Veterinary Services (VS) to reduce Michigan’s TB status. The reduced status places significant burdens on producers selling cattle interstate. While VS has considerable experience and success in eradicating TB from cattle, eradicating TB from wildlife presents a very new scientific and social challenge. This paper outlines the progress of eradication efforts undertaken by Michigan Department of Natural Resources and USDA-APHIS–Wildlife Services (WS). Methods used include reducing deer numbers through hunting, regulating the feeding and baiting of deer, special permit shooting, barriers, and a 2004 pilot project that identifies and removes suspected TB-positive deer.

Cervid disease research at the National Wildlife Research Center

The realized and perceived threats of cervid diseases have immense implications for federal and state wildlife management agencies, captive cervid ranchers, hunters, and businesses and economies that rely on recreation associated with deer and elk. Therefore, the spread of diseases, primarily chronic wasting disease and bovine tuberculosis, in wild and captive cervids is of great concern. Research is paramount to closing information gaps associated with all aspects of cervid diseases. The Wildlife Disease Research Program of the USDA APHIS WS National Wildlife Research Center is engaged in considerable research on cervid diseases. Efforts focus on disease epidemiology, cervid ecology, and methods to reduce disease prevalence and transmission. Here we share results of recently completed studies, provide updates for ongoing studies, and share plans for upcoming research

Epizoology and response to the bioweapon use of the plague organism, Yersinia pestis, in commensal rodents

The increased risk of terrorism with biological agents has been well documented. In response, the United States has established an extensive infrastructure to counteract deliberate disease epidemics that would follow bioterrorism attacks. The plague organism, Yersinia pestis, has been identified as a Category A biological agent by the Centers for Disease Control and Prevention. The response to the use of Y. pestis as a bioweapon, aerosolized and released to a target population, would first involve the treatment and containment of the disease in humans. As the initial impacts of the first round of human infections occur, the possibility exists that the disease could infect commensal rodent populations. If the disease were to progress in rodents, the rodents would suffer mortality and their plague-infected fleas would seek new hosts, potentially including human hosts, and cause a second disease epidemic in humans. This paper outlines the epizoology of the bioweapon use of Y. pestis to commensal rodents, identifies U.S. localities of concern, and suggests control and surveillance strategies in response to a bioterrorism attack of this nature.

Leptospirosis in the Azores: The rodent connection

The Azores are Portuguese islands in the North Atlantic Ocean. The culture is very agrarian with a large cattle industry. Unfortunately, there is a chronic leptospirosis problem within the people, livestock, companion animals, and wildlife of the Azores. Introduced rodents play a significant role as maintenance hosts of this disease. We review the situation and make recommendations for reducing the occurrence and hazard of leptospirosis in the Azores. Areas addressed include the need for a better understanding of the epidemiology of the disease and the role of rodents, development of an effective rodent control program, improvements in farm practices and animal husbandry, and improvements in the Azores infrastructure to effectively reduce the leptospirosis hazard.

Development and use of Compound 1080 in coyote control, 1944-1972

Compound 1080® is a man-made sodium salt of fluoroacetic acid or fluoroacetate, which occurs in nature as the toxin in many species of poisonous plants. The toxicity of such plants had long been recognized, but the toxic agent was not identified as fluoroacetate until 1944. By that time, the pesticidal potential of synthesized sodium fluoroacetate (code number 1080-44) was being explored in the United States in wartime, crash program aimed at finding new rodenticides. Compound 1080, the main product of that program, proved to be the best rodenticide known up to that time. It was found to be even more toxic to canids than to rodents, so was used experimentally for coyote control beginning in November 1944. Compound 1080 was authorized for operational use in governmental predator control in 1946. Large meat baits, or bait stations, injected with 1080 solution and placed on livestock ranges in winter quickly became a preferred method for reducing coyote populations that preyed on sheep and cattle. The use of 1080 bait stations peaked in Fiscal Year (FY) 1963, when over 16,000 stations were placed by the U.S. Fish and Wildlife Service Predator and Rodent Control program. After 1963, numbers of 1080 stations declined year by year to 1972 when the use of 1080 and other predacides on Federal lands and in Federal programs was stopped by President Nixon’s Executive Order 11643, followed by Environmental Protection Agency suspension and cancellation of registrations for 1080 and other predacides. The 1080 cancellation was based partly on high potential hazard to humans, even though no human had ever been killed or seriously injured in connection with the use of this toxicant in coyote control. Paradoxically, most of the political agitation over Compound 1080 focused on its use in predator control, even though much greater amounts were used for rodent control. The total amount of 1080 sold in the U.S. during 1968-1972, the last 5 years in which 1080 bait stations were used, was approximately 10,003 lb. Only 1.3% (129 lb) of that amount was used for predator control. The largest amount of 1080 used for coyote control in the United States in any one year was about 42.4 lb, in FY 1963.

1080, toxic sugars, alkaloids, and a dead cat: The search for a toxicant in Australian Gastrolobium seed

It was hypothesised that reintroduction of Australian native mammals, currently being severely impacted by feral cat predation, would be more successful if these mammals could have a retained toxicity as discussed in historical accounts. Seeds from the Australian genus Gastrolobium (Fabaceae: Mirbelieae) were analysed in the search for a toxicant that would explain historical accounts of toxic wildlife. Numerous accounts referring to bronzewing pigeons having toxic bones were specifically noted. Analysis of this seed found no evidence for rapidly toxic alkaloids previously reported as being extracted from the leaves of York Road poison and box poison. However, evidence for the presence of organo-fluorine compounds in addition to the reported fluoroacetate (Compound 1080) was discovered. A limited cat dosing trial found that a highly fluorinated box poison seed caused a cat to cease respiration in 82 minutes, but its chloroform extract produced no adverse physiological response. In addition, citrate accumulation appeared more rapid and acute with increasing seed ‘total fluorine.’

Non-target hazard to ring-necked pheasants from zinc phosphide use in northern California agricultural areas

The National Wildlife Research Center (NWRC) conducted a field study to determine hazards to non-target gallinaceous birds following the use of 2.0% zinc phosphide (Zn3P2) baits for vole control in fall alfalfa. Consultation among the NWRC, USDA Wildlife Services, California Department of Food and Agriculture (CDFA), U. S. Environmental Protection Agency (EPA), and the California Department of Fish and Game produced a 3-phased study. Free-ranging ring-necked pheasants and California quail were studied in alfalfa during the concurrent harvest of other agricultural crops. These data would be used by CDFA to support the re-registration of their label “Rodent Bait Zinc Phos­phide Treated Grain (2.00%)”, EPA Reg. No. CA890027. Phase 1 was a pilot study to determine whether the two test species could be maintained in walled enclosures. Phase 2 was a worst-case-scenario using the test species in alfalfa enclosures during vole control (i.e., simulated field study). Information from the 14-day post-baiting period led to a better understanding of some variables, including the sub-lethal effects that could impact the design of the final phase. During Phase 3 the actual non-target field study was conducted. Results from Phase 1 showed that these species could be maintained in outdoor enclosures using only wing clipping, 1 m-high metal walls, and no covering nets. Phase 2 proved that in outdoor alfalfa enclosures, baiting for vole control was not hazardous to quail but might be to pheasants. Phase 3 concluded that 2.0% Zn3P2 bait when applied per label directions was not hazardous to either wild or pen-reared free-ranging pheasants in fall agricultural areas. This article summarizes the 3-phased study, the resulting data, and conclusions.

Field efficacy of Fumitoxin® (55% aluminum phosphide) tablets for controlling valley pocket gopher

This field efficacy trial using aluminum phosphide tablets for controlling the valley pocket gopher was conducted on land farmed by California State Polytechnic University, Pomona, California. The treatment blocks were located in moderate to heavily infested cover crops in deciduous orchards. Each of 2 treatment blocks contained 10 study plots, as did 2 control blocks. All burrows in the treatment blocks as well as a 100-foot-wide buffer were treated by placement of 2 to 4 Fumitoxin® tablets in each of 1 to 3 probed holes. Both treatment units had a 90% decline in pocket gopher activity, judged by the open hole census method, after the first treatment, and 100% reduction after burrows missed in the first treatment were treated. All burrows in the control plots remained active throughout the entire trial. All treatment points in the study plots were flagged and 33%, including 6 burrows remaining active in the 2-day post-treatment period, were examined for proper tablet placement. The importance of proper aluminum phosphide tablet placement is discussed.

A novel technology for the control of rodents

An alternative rodent control technology is presented. The patented discovery that specific plant-derived structural carbohydrate polymers are inhibitory to the water retentive mechanisms of rodents is discussed. Specifically, it has been discovered that when natural complex structural carbohydrates are formulated into a palatable pellet, target species of rodents (rats, mice, and ground squirrels), after ingesting the polymers, become less active and eventually die after 3 - 10 days. Captivity and in situ tests on the Norway rat have indicated the lethal dose for rats to be approximately 35 - 50 g consumed over a period of 72 - 96 hours, whereas for house mice it is 7 - 10 g over the same period. Captive trials on California ground squirrels have indicated a similar lethal dosage to that of rats, specifically 35 - 50 g consumed over 72 - 96 hours. The commercial product is exempt from registration in many countries including the U.S. This paper discusses laboratory and field test results on rodents to date and field use experiences.

Evaluation of three contraceptive approaches for population control of wild horses

Overpopulation of feral horses in several western states is an unquestioned problem. Current management strategies of removal and adoption are expensive, logistically challenging, and ineffective as a means of population control. We are testing three long-acting contraceptive approaches on feral Nevada mares. Modified reversible immunocontraceptive vaccines for gonadotropin releasing hormone (GnRH) and porcine zona pellucida (PZP) (SpayVac), and intrauterine contraceptive devices (IUDs), are being evaluated to determine: 1) their safety and efficacy for preventing pregnancy for multiple years, 2) whether the effects are reversible, and 3) whether there are notable contraindications. Preliminary data after 1 year suggest that IUD- and PZP-treated mares continue to exhibit breeding and estrus, while GnRH-treated mares are less likely to cycle. All mares in the GnRH and PZP treatments were infertile for the breeding season. Eighty percent of the IUD-treated mares were infertile; those mares that became pregnant likely failed to retain the IUD. A notable contraindication was that uterine edema normally observed in mares in the follicular phase of the estrous cycle was commonly observed in PZP-treated mares. Because administration of each contraceptive approach is different, and each has different effects and expected duration, one approach or a combination of approaches may be best suited for specific field applications. Subsequent years of this study should establish the efficacy and safety of one or more long-acting contraceptive approaches for feral horse population control.

GonaCon,™ a versatile GnRH contraceptive for a large variety of pest animal problems

As part of the program to develop contraceptive tools to control populations of over-abundant wildlife species, the NWRC has developed a single-injection gonadotropin-releasing hormone (GnRH) immunocontraceptive vaccine, GonaCon™. GonaCon™ has been tested and shown to provide contraceptive effects lasting 1-3 years in many pest species including white-tailed deer, domestic and feral pigs, bison, wild horses, cats, dogs, and California ground squirrels. GonaCon™ contains a GnRH peptide conjugated to keyhole limpet hemocyanin combined with AdjuVac™, an adjuvant also developed at the USDA National Wildlife Research Center. Immunization against GnRH prevents the circulating GnRH from stimulating the release of pituitary luteinizing hormone and follicle-stimulating hormone. This process of immuno‑neutralization of GnRH effects a temporary non‑surgical castration in both males and females. Contraceptive and behavioral effects of GonaCon™ are discussed for a variety of species.

Fertility control of California ground squirrels using GnRH immunocontraception

Populations of wildlife, such as California ground squirrels, can grow to the extent that they come in conflict with humans. Contraception is a method of population management under investigation that may be useful in situations where neither leaving the animals uncontrolled nor lethal control are apropos. In this study, we tested the use of a single-injection gonadotropin releasing hormone (GnRH) immunocontraceptive vaccine in urban California ground squirrels. We monitored the effects of treatment for two breeding seasons. Immunization reduced the proportion of females lactating by 91% the first year and 96% in the second year. Testicular development was inhibited 35% the first year and 89% the second year. There is a delay of several months from the time of injection to inhibition of testes development. Reduction in the number of juveniles born per adult as determined by a visual count index was 9% the first year and 66% the second year. This study shows that the single-shot GnRH vaccine is over 90% effective for at least 1.5 years and requires several months after immunization for contraceptive effect. Because the immunization requires injection, it is labor intensive, but it is much more practical than treatments requiring multiple administrations to the same animal. GnRH immunocontraception may be a useful tool in rodent population management in certain circumstances.

Reproductive control of vampire bat (Desmodus rotundus): An environmentally friendly alternative

Vampire bat control strategies have not changed in México for more than 40 years. Anticoagulants and strychnine are frequently used to reduce bat populations and the prevalence of rabies. Despite these control efforts, vampire bat-borne rabies continues to have a significant economic impact. A new control method is being developed that takes advantage of the reproductive changes induced by phytoestrogens in mammals. In this study, we fed bats the phytoestrogen coumestrol, for 30 days and examined its effect on the reproductive organs of male and female vampire bats in laboratory tests. For males, coumestrol resulted in an increase in weight and loss of the typical histological structure of testes. Treated females had no corpora lutea in their ovaries and fewer primordial folliculi were observed. These results suggest that coumestrol might be a candidate replacement for anti-coagulants used for vampire bat control.

Emergency wildlife management response to protect evidence associated with the terrorist attack on the World Trade Center, New York City

At the request of the New York City Police Department, the Port Authority of New York and New Jersey, and the New York State Department of Environmental Conservation, a team of USDA APHIS Wildlife Services (WS) biologists mobilized in less than 24 hours to assist federal, state and local law enforcement officials in managing birds and rodents impacting the recovery of evidence as a result of the September 11, 2001 terrorist attacks on the World Trade Center. During the 10-month recovery effort from September 2001 to June 2002, more than 1.7 million tons of debris was shipped from “Ground Zero” in Manhattan to a high-security crime scene at the Fresh Kills Landfill (FKL), Staten Island, New York. Close to a billion pieces of debris were sorted by law enforcement officials to recover personal effects, human remains, and other evidence to document the crime and identify victims, as part of the largest forensic investigation in U.S. history. Within days of bringing debris to FKL, more than 2,600 gulls were on site, disrupting work of law enforcement officials and creating a concern that evidence would be lost to birds. Historically, FKL has been a feeding and loafing site for over 100,000 gulls. To address this unprecedented wildlife damage management problem, WS implemented an integrated bird and rodent management program that involved 69 biologists from 23 states. The goal was to reduce the impact of gulls, crows, house mice, and Norway rats on law enforcement personnel, equipment, and evidence collection including a zero-tolerance policy for gulls and crows landing on the working face. A combination of population surveys and direct management activities targeting gulls and crows was initiated 12-14 hours a day, 7 days a week using visual and noise deterrents including pyrotechnics, mylar tape, human and dead-bird effigies, lasers, paint ball guns, and lethal removal of a limited number of birds. In addition, commensal rodent surveys with snap traps were conducted twice monthly to document population trends and explore the need for rodent control on site. We deployed over 23,000 pyrotechnics and dispersed over 172,000 gulls and 5,000 crows from the site. We removed 293 house mice and 46 Norway rats in 6,000 trap-nights. The program was highly effective in preventing gulls and crows from feeding on remains and disrupting workers. We discuss other key lessons learned regarding an emergency response program to manage wildlife.

The Office of Spill Prevention and Response -- Applying bird hazing techniques in oil spill situations

This paper provides historical background on the Office of Spill Prevention and Response (OSPR) and describes the functions and capabilities of the Hazing Group within OSPR with regard to protecting wildlife during oil spills. In response to the oil spill disasters of the tankers Exxon Valdez in Alaska and the American Trader in California, legislators in 1990 created OSPR within the California Department of Fish and Game and gave OSPR substantial authority to oversee spill clean-up, natural resource damage assessment activities, and wildlife protection activities. In view of the potential for high bird mortality during a spill event and the high costs for rehabilitation, OSPR established the Hazing Group with the goal of preventing birds from becoming exposed in the event of a spill. The primary responsibilities of the Hazing Group are to: 1) improve and maintain preparedness and hazing response capabilities for spill events, 2) obtain or provide training and training materials on hazing techniques and strategies, spill response procedures, and other related subjects both for wildlife hazing unit members and other appropriate OSPR responders, and 3) conduct and review research on wildlife hazing techniques and strategies appropriate for spill events. With regard to response capabilities, the Hazing Group is on call 24 hr/day, acquired and maintains an inventory of pyrotechnics and other hazing equipment, has a cargo trailer on stand-by loaded with equipment and supplies sufficient for several days, and assembled a collection of California coastline maps useful for response planning. Training required for Hazing Group personnel includes HAZWOPER certification with an annual refresher course. Other training includes an annual Incident Command System class and participation in drills and exercises. A hazing manual is under development as training material for Hazing Group and other OSPR personnel. The Hazing Group conducted a literature review of research on bird hazing techniques and produced an annotated bibliography on bird hazing techniques applicable to oil spills. As oil spills are relatively short-lived events, techniques with only short-term effectiveness may still be sufficient for hazing birds.

Wildlife conservation sunflower plots as a dual-purpose wildlife management strategy

The National Sunflower Association has identified blackbird damage as a key reason for growers to abandon sunflower. In the 1980s, National Wildlife Research Center scientists showed that “decoy” plantings of sunflower can significantly reduce bird damage to nearby commercial sunflower fields. For a variety of reasons, largely logistical and economic in nature, decoy sunflower fields did not become wide-spread. Over the last decade, new federal farm programs have placed more emphasis on wildlife conservation. Thus, decoy sunflower fields planted to ameliorate blackbird damage and establish habitat for wildlife might garner broad support from both agricultural and conservation groups. We present preliminary data on avian use of ripening sunflower fields that support the notion of “Wildlife Conservation Sunflower Plots” (WCSP) as a broad-based dual-purpose wildlife management strategy. We also outline research plans designed to refine the concept of WCSP.

Wildlife hazard management at airports: Fifteen years of growth and progress for Wildlife Services

In the 1990s, major concurrent expansions occurred with commercial aviation and populations of bird and other wildlife species considered hazardous to aviation. These parallel trends resulted in increased numbers of wildlife collisions with aircraft (wildlife strikes) that now cost USA civil and military aviation more than $500 million annually and pose a threat to flight crews and passengers. The USDA Wildlife Services (WS) program responded to these increased conflicts by developing an integrated, science-based program of technical and operational assistance for the aviation industry to reduce wildlife hazards at civil and military airports. This WS Airports Program was based on a foundation of 3 initiatives. The first was Memoranda of Understanding developed in 1989-1990 between WS, the Federal Aviation Administration (FAA), and the Department of Defense (DoD) which state that the FAA, certificated airports, or DoD facilities may request assistance from WS to reduce wildlife hazards to aviation. A second initiative was an interagency agreement between FAA and WS in place since 1991 that charged WS to research new methods to reduce strikes and to develop a National Wildlife Strike Database. A third initiative was an Airports Training Course developed by WS that has certified 247 WS biologists and technicians to work on airports, 1996-2003. As a result of these initiatives, WS provided assistance in assessing hazards and reducing risks posed by wildlife at 565 airports in 2003 compared to only 42 in 1990. Accomplishments of the WS Airports Program since 1990 are discussed through case studies. These studies include: 1) the development of the 57,000-record National Wildlife Strike Database, which provides a scientific foundation for WS work at airports; 2) applied research projects resulting in new information and techniques for reducing strikes; and 3) integrated wildlife damage management programs at airports that have resulted in significant reductions in wildlife strikes.

Cooperative mitigation of wildlife attractants between an Air Force base and the local community

Seymour Johnson Air Force Base (SJAFB), North Carolina lies within the Atlantic Flyway waterfowl migration corridor and is home to the 4th Fighter Wing (4FW), with 4 fighter squadrons and 2 training units, and the tenant 916th Air Refueling Wing (916 ARW), operating 10 KC-135R Stratotankers. To allow the 4FW and 916 ARW to continue their operations at SJAFB, the City of Goldsboro must maintain the safety of the military’s assets. This includes ensuring that land usage within a 5-mile radius of the base is compatible with safe flight operations (e.g., areas should not attract large populations of birds). Over the last 3 years, $4 million in damage to SJAFB aircraft was caused by duck, goose, gull, and vulture strikes. These birds are known to utilize wetlands, ponds, and quarries surrounding the base. With populations of these birds increasing around SJAFB, the addition of incompatible land uses could cause the city and surrounding region to lose $340 million per year in revenue if the base was to relocate due to safety concerns related to striking birds. The economic value of the base has helped prompt city officials to coordinate with the base before granting permits for new land uses. The city also has recognized the need to reduce the abundance of birds currently using the wetlands and ponds adjacent to the SJAFB airfield.

Evaluating population management scenarios: Crunching the numbers before going to the field

Efforts to mitigate wildlife-human conflicts typically involve management of unacceptably abundant populations. Increasingly, however, reduction of dense or increasing populations of certain wild species evokes both support and contention from the public. Management decisions involving population reduction, particularly those directed at highly visible species, should therefore be based on quantitative evaluation of potential outcomes prior to implementation. The purpose of this paper is to revisit a call for use of population modeling in management decisions by reviewing basic aspects of population analysis and the use of publicly available long-term data sets in environmental assessments and impact statements. Our objectives are to discuss 1) the relationship of population parameters to population growth, 2) methods of population projection, 3) use of data for model calibration and validation, and 4) the evaluation of management scenarios. Justification and defense of lethal or reproductive control programs to solve vertebrate pest problems requires a sound understanding of population status and the dynamics of the problem species.

Nevada wildlife resource protection overview: 2000 through 2003

In January 2000, The Nevada Board of Wildlife Commissioners directed the Nevada Division of Wildlife (NDOW) to contract with the United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services Program (WS) to conduct wildlife damage management (WDM) activities for the protection of certain species of Nevada’s wildlife. Responding to the Commission’s directive, the NDOW requested WS to initiate protection of a variety of avian and mammalian wildlife resources that they deemed in need of special protection from “excessive predation”. Nevada has a greater percentage of publicly owned/managed lands than any other state in the nation – about 86% – so most of the wildlife resources requiring special protection from predators are located on federal lands, usually Bureau of Land Management (BLM) or United States Forest Service (USFS) lands. Because the natural resources to be protected were on public lands, WS was required to develop Annual Work Plans prior to conducting WDM activities that fulfilled WS’ mission and conformed to BLM’s and USFS’ land use plans. Prior to initiating any WDM actions, WS personnel conducted predator avian/mammalian surveys to monitor targeted predator populations. Additionally, WS conducted predator avian/mammalian surveys throughout the ongoing WDM activities, as well as shortly thereafter, to monitor targeted predator population levels. WS personnel directed their actions toward the surgical removal of those species deemed problematic by NDOW (mountain lions, coyotes, common ravens, magpies, and badgers), depending on the resource to be protected, the specific locations where protection was deemed necessary, and during the specific period of the year when damage occurred. Results from WS’ WDM activities on these projects were reported by NDOW, the management agency responsible for managing Nevada’s wildlife. As an added benefit to the resource protection work, WS took blood samples from all avian and mammalian predators removed during WDM activities in order to monitor wildlife diseases via testing conducted by the Centers for Disease Control or the Nevada Department of Agriculture’s Animal Testing Lab.

Ecology, genetics and socio-biology: Practical tools in the design of target-specific feral pig baits and baiting procedures

Feral pigs occupy 40% of Australia along with numerous other countries. They cost Australian agriculture greater than AUD$100 M annually through stock predation and crop, pasture, and infrastructure damage. Broad-scale, integrated poisoning campaigns, predominantly using Compound 1080, are the most practical and cost-effective control method in Australia. However, the lack of a target-specific toxicant and bait for feral pigs means that baiting campaigns can place non-target species at risk. Confounding this is the wide distribution and diet of feral pigs in Australia, which means that no current single bait is effective for all feral pigs. A potential solution to this problem is to use the known ecology, genetics, and socio-biology of feral pigs in different habitats to design bait(s) with increased target specificity, then combine this with habitat-specific operating procedures inferred from ecological and genetic studies to reduce non-target exposure. This process is currently underway in Australia. Habitat-independent characteristics of feral pigs that can be used to develop target-specific baits are their large size and strong jaws, their keen sense of smell, their poor vision, their omnivorous diet, and their nocturnal and fossorial nature. Producing large, tough, odorous, dyed (to deter birds), meat and vegetable (to deter obligatory carnivores or herbivores) baits that are laid at night and buried where possible will make feral pig baits more target specific and reduce non-target exposure. Current pen and field trials of bait prototypes in a range of habitats are confirming this. Appropriate baiting regimes for feral pigs in different habitats, as determined through ecology and genetics and subsequent field trials, are presently being determined and transformed into standard operating procedures to lessen non-target exposure. The planned incorporation of more target-specific toxins or ‘Achilles Heel’ approaches in the future should further increase the target specificity and humaneness of broad-scale feral pig control. This protocol can potentially improve target-specificity of baits and baiting procedures for other pest animals.

Efficacy of black bear supplemental feeding to reduce conifer damage in western Washington

While searching for food, one black bear may girdle 60 - 70 coniferous trees in a day during the spring months in western Washington. Tree-bark peeling and subsequent foraging on sapwood can result in substantial economic losses for forest landowners. The supplemental feeding program, a nonlethal approach to minimize black bear damage by providing an alternative food source, was developed by the Washington Forest Protection Association in 1986. From 1998 to 2002, I studied the efficacy of this supplemental feeding program on the Olympic Peninsula. I selected 14 conifer stands of approximately 20 ha each for study. Mean pretreatment conifer damage on these sites in 1998 was 26% of trees. In March 1999, 1,000 trees were marked on 4 transects throughout each stand. Two feeding stations were installed on each of 7 randomly chosen stands in April of 1999, while no supplemental feed was supplied on the remaining 7 control stands. I found that bears damaged significantly more trees on control sites than on treatment sites (P < 0.001). To validate initial results, I removed feeding stations from 2 of the 7 feeding sites in July 2000. Damage increased by a factor of nearly 7 on one feeding site over the next 2 years. I concluded that the supplemental bear feeding program constituted a viable, nonlethal damage control tool.

An overview of the significance and management of vertebrate pests around zoological parks

Zoological parks provide ideal environments for a wide range of vertebrate pests, while at the same time presenting several unique challenges relative to the methods and materials employed for suppressing or eliminating vertebrate pest populations. As a result, zoo park pest management programs must be very carefully designed and implemented. Each of the most significant vertebrate pests requires a species-specific approach within a quality Integrated Pest Management (IPM) framework. Underlying this framework is a necessity for high level cooperation and communication between administrators, veterinarians, individual zookeepers, groundskeepers, pest management personnel and all contracted vendors servicing the park. Because the scope of vertebrate pest management is so broad– especially in the context of a zoo park environment– this paper presents an overview but guides the reader to the appropriate sources of additional pest management information for each particular pest group.

Effects of forage nutritional quality (energy and protein) on deer acceptance of foods containing secondary metabolites

Deer foraging on tree seedlings is recognized as the most widespread detriment to reforestation efforts. Non-lethal approaches to reduce deer damage to seedlings are highly desirable. Avoidance of natural secondary metabolites contained in conifers may provide feasible means to develop non-lethal measures. Other studies have demonstrated that sheep and goats fed diets with high protein-to-energy ratios, or allowed to select between concentrates high in either energy or protein, ate much more of a high-terpene diet and of a high-tannin diet than when they were fed diets high in energy-to-protein ratios. Thus, manipulating foraging options for deer may impact their ability to ingest terpenes contained in conifers. We conducted a series of studies to determine whether deer acceptance of terpene-containing foods can be affected by altering the ratio of energy and protein in their maintenance diet. We determined relative consumption of a high-energy and low-protein diet, and a low-energy and high-protein diet, when deer are given the opportunity to self-regulate their intake. We also determined if deer modified their relative intake of these diets when offered an alternative terpene-treated diet. Penned deer were offered variable diets (e.g., high energy-low protein, low-energy-high protein, or both foods), then their acceptance of terpene- and tannin-containing foods was determined. Deer consumed more and demonstrated a strong preference for the high-energy diet relative to the high-protein diet. However, the varied diets did not appear to affect their intake of terpene or tannin-containing foods. This paper discusses the potential of manipulating maintenance rations as a non-lethal tool, presents initial results and possible explanations for differences between our study with deer and prior work with domestic ruminants.

Economics in wildlife damage management studies: Common problems and some solutions

Benefit-cost analysis (BCA) has become a highly useful economic tool to evaluate research and operational efforts in wildlife damage management. At the same time, common problems with BCA can be noted in these studies. These problems include: the absence of present value calculations, the misuse of market vs. non-market valuations, and the improper accounting of benefits and costs. Solutions to these problems are relatively simple but are imperative to the accuracy of the results. This paper outlines a number of common errors in BCA and offers solutions that enhance the use of economics in wildlife damage management studies.

California’s rodenticide surcharge program: History and accomplishments

In 1990, the California Legislature passed a law to collect a $0.50 per pound surcharge on all vertebrate pest control materials sold by county agricultural commissioners throughout the state. These monies were to be used to fund research required to maintain the state’s current vertebrate pesticide registrations, to improve existing rodenticides, and to find new materials and methods to solve California’s vertebrate pest problems. An external advisory committee, the Vertebrate Pest Control Research Advisory Committee, was established to set research priorities and recommend expenditures from this fund. To date, this program has raised more than $6.5 million to meet its objectives. We summarize the history and operation of the surcharge fund as well as the accomplishments of the program. Data on rodenticide sales throughout this program’s operation are presented. We describe the types of research funded to date, as well summarizing results of selected studies supported by this program. We also review accomplishments in education and outreach supported by this fund.

USDA Wildlife Services image collection: Creating an online database of digital images using CONTENTdm™ software

Photographic images are valuable assets in wildlife damage management research. Photographs are used in presentations, publications, websites, and posters to illustrate damage problems, the species involved, and management solutions. However, organizing photographic collections is time consuming, requires special storage, and locating individual images becomes difficult as collections grow. This article demonstrates the USDA Wildlife Services Image Collection Database and describes the steps taken in creating the database, scanning the images, developing a controlled vocabulary and metadata, and Internet search screens. The database allows users to search by keyword, display search results, and download selected images directly into PowerPoint to create presentations. Plans for future additions to the database are also discussed, and recommendations on organizing individual image collections are listed.