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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:

Salmon, Terrell P. 2012. VPC: Fifty Years of Progress? Proc. Vertebr. Pest Conf. 25:3-6.

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.


Population dynamics: The foundation of wildlife damage management for the 21st century

To justify and defend lethal or reproductive control programs to solve vertebrate pest problems, wildlife biologists must have a sound understanding of the population status and dynamics of the problem species. Models are essential to project how populations will respond to proposed management actions, providing a scientific foundation to counter the emotional debates that often arise. Four population models (PM1 to PM4) for predicting population responses are described. PM1 and PM2 explore the relative efficacy of reproductive and lethal control for vertebrate species over 10-year intervals. PM3 simulates population responses to actual management actions through 10-year intervals. PM4 simulates population changes for a species at weekly intervals over an annual cycle, exploring the immediate (≤1 year) impact of population management actions. Population simulations using PM1 and PM2 demonstrated that for most vertebrate pest species considered, lethal control will be more efficient than reproductive control in reducing population levels. Reproductive control is more efficient than lethal control only for some rodent and small bird species with high reproductive rates and low survival rates. A simulation (PM3) of the removal of 47,000 laughing gulls (Larus atridlla) from the Long Island-New Jersey population accurately predicted the 33% decline of the population over five years. A simulation (PM4) of the annual cycle of the common grackle (Quiscalus quiscula) population in the eastern United States demonstrated why removing 4.2 million birds in one winter had no discernible impact on subsequent breeding populations. Understanding the population dynamics of wildlife species is the cornerstone to successful management, and population models will be essential for this task in the years to come.

The beaver--a southern native returning home

Beaver populations, extirpated in the previous century, have returned to the South often causing severe damage to timber and other resources. Many landowners perceive trapping programs as being ineffectual, perhaps because most programs are overwhelmed with immigrant beavers. To quantify immigration patterns, from November 1984 to May 1985, resident beaver were removed from a 1,619 ha study area in west Tennessee and for the next 40 months immigrants were captured within one month of immigration. Removal patterns of the resident population (169 beavers) suggest that bounty systems may be ineffectual to protect natural resources. Immigration was low (5.5 beavers) June to September and significantly (P≤0.05) higher (46.4 beavers) October to May.

The potential for managing urban Canada geese by modifying habitat

Urban Canada goose (Branta canadensis) populations have grown rapidly during the past three decades. This paper reviews short-term and long-term urban goose management techniques, and using data for the Twin. Cities of Minnesota, assesses the potential utility of habitat modification. Ninety-four percent of Twin Cities damage complaints occurred during the brood-rearing period, 5% in fall, and >1% in spring and winter. The potential for reducing goose damage by altering nest habitat is insignificant, brood-rearing habitat high but expensive, and fall and winter habitat low and also costly. Fences effectively thwart flightless geese but can entrap birds leading to starvation. Cost projections for programs limiting the Twin Cities summer population at 25,000 were $125,000/year for relocation, $325,000/year for processing for human consumption, $12.3 million/25 years for wire fences, $33.9 million for tall grass prairie, and $1.8 billion for ground juniper (Juniperus spp.). Human preference for savanna and the fear of urban crime associated with dense vegetation may hamper implementation of goose habitat modification.

Conservation implications of feral pigs in island and mainland ecosystems, and a case study of feral pig expansion in California

Feral pigs (Sus scrofa) are an exotic ungulate which have been widely introduced worldwide with multiple ecosystem and economic consequences. The author conducted a semi-comprehensive literature review directed at identifying the current state of knowledge related to the effects of feral pigs on island and mainland plant and animal communities. Also, the author describes the situation in California where feral pigs that were introduced in the late 1700s are now widespread due to hunting-related introductions and natural range extensions. Feral pigs on predator-free oceanic islands are a serious conservation problem because they attain high densities and have contributed to near-extinctions and extinctions of multiple endemic plants and vertebrates. In mainland ecosystems, however, feral pigs can have both positive and negative effects depending on the local circumstances. Rooting, for example, can have both positive and negative effects on growth and survival of some trees, soils and soil processes, and the distribution of native and exotic grasses. In general, however, the negative effects of rooting by feral pigs are amplified when population densities are high. Feral pigs may compete with native species for limited resources, but there are limited data relevant to this hypothesis. Based on observations of small amounts of animal matter in their diets, feral pigs eat terrestrial vertebrates and eggs of ground nesting birds, but the importance of predation by feral pigs on native vertebrates is poorly known. Feral pigs also may have important indirect effects in mainland ecosystems by providing a new prey base for native predators which may then increase. In areas of Europe with extant wolf (Canis lupus) populations, wild boar (Sus scrofa) are an important prey species which may be facilitating numerical and geographic recoveries of wolves. Because wild boar are important prey for endangered Amur tigers (Panthera tigris), they are considered important for recovering tiger populations. In Australia, feral pigs are potentially important prey for dingoes (Canis familiaris dingo); whereas, in the United States, endangered Florida panthers (Felis concolor coryi) consumed 23% to 59% feral pigs, and mountain lions (Felis concolor) in Texas and California consumed 5% to 38% feral pigs. Research needs for feral pigs include quantitatively assessing: 1) how acorn foraging by feral pigs limits or influences regeneration of oaks (Quercus sp.); 2) the competitive effects of feral pigs on native species; 3) whether direct predation by feral pigs suppresses small vertebrate populations; and 4) how the availability of feral pigs as prey influences native predator populations.

Tracing the history of blackbird research through an industry's looking glass: The Sunflower magazine

The Sunflower magazine, the voice of the National Sunflower Organization, featured articles in January 1978 and December 1996 that began with these words, "If Old King Cole was a merry old soul, it was probably because he had only four and twenty blackbirds to contend with, and they were all out of commission!" This quotation captures the sentiments of sunflower growers, who have identified blackbirds as a major production problem since the 1960s. The National (formerly Denver) Wildlife Research Center, a unit within the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service Wildlife Services, is charged with both improving and developing new methods for managing blackbird damage to sunflower. The Sunflower has chronicled these research efforts championing studies with clear objectives and opposing studies, sometimes vehemently, that use resources for seemingly esoteric research. In this paper, the history of blackbird research in the northern Great Plains is traced through The Sunflower

The use of netting as a bird management tool in vineyards

Vineyard bird control is an important issue both monetarily and practically. Each season vineyard managers face the real threat of significant crop loss to starlings and finches, as well as an assortment of other birds. The increased popularity of wine as a mainstream consumable has led to a higher crop value in this industry. Because of this, the grape growers can no longer ignore bird damage. Netting, now recognized as the best solution, creates an additional challenge for the grower. To take full advantage of this management tool, a working knowledge of the proper equipment, as well as recognition of the behavioral characteristics and effects of the pest birds, must be combined for maximum effect.

Population trends and ecological attributes of introduced parrots, doves and finches in California

At least 10 species of parrots (Family Psittacidae). along with the Eurasian collared-dove (Columbidae: Streptopelia decaocto), orange [northern red] bishop (Ploceidae: Euplectes frandscanus), and nutmeg mannikin ["spice finch" or "spotted munia"] (Estrildidae: Lonchura punctulata). have recently established significant viable and generally increasing populations in California. Populations of all of these taxa are concentrated in highly modified urban and suburban habitats (parrots, doves) or in flood control basins and river channels with abundant rank annual growth (bishop, mannikin). With various collaborators, the author has monitored these taxa in southern California through the 1990s. Because of the potential for deleterious ecological interactions with native bird species and for damage to certain commercial crops, monitoring of these species and other potentially established exotic bird species must be ongoing. Here the author reports his present knowledge of population sizes and trends, geographical distribution, habitat relationships, and foraging and breeding ecology of these introduced species and suggest schemes for continued monitoring.

Monk parakeets in the Unites States: population growth and regional patterns of distrubution

Records from Christmas Bird Counts were summarized to assess population growth of the Monk parakeet (Myiopsitta monachus) in the United States from 1975 to 1996. Population growth over this period fits an exponential model of population growth with a current annual rate of increase of 12.9% and a doubling time of 5.4 years. Since 1990, however, population growth on a national scale has slowed considerably, suggesting that the species may be approaching a carrying capacity. In contrast to the results across the entire United States, the population of monk parakeets in northeastern Illinois has dramatically increased in numbers within the last decade. In this region, the Hyde Park, Chicago population appears to be acting as a source from which other areas are colonized. The monk parakeet is known to have caused damage to fruit crops in Florida, and they can be a nuisance species to local utility companies when they build their nests on power transformers. Nevertheless, such damage is highly localized and, on a national scale, there is no evidence to date that monk parakeets should be considered a pest species and subject to widespread control. The initiation of detailed studies of a banded population of this species is recommended

The U.S. Air Force bird avoidance model

The United States Air Force reports approximately 3,000 bird strikes to its aircraft annually, which cost nearly $50 million on average. In the last decade, the Air Force has suffered the loss of 14 aircraft with 33 aircrew fatalities. For military aircraft, the majority of catastrophic incidents occur on high-speed, low-level, and range missions where bird control is not possible. The only alternative in these environments is to avoid known bird concentrations. The Bird Avoidance Model (BAM) is a Geographic Information System (GIS)-based program that integrates historical information on bird distributions and abundances with various geographic and environmental factors. It creates graphic risk surfaces for determining the relative degree of hazard for any location in the Continental U.S. The initial version of the model includes over 50 species considered most hazardous to flight operations. Large birds, such as waterfowl and raptors, and flocking species, such as blackbirds and gulls, constitute the greatest threat. The user interface for the new BAM is a simple, menu-driven, PIC-based program that allows flight planners, route designers, and aircrew to select the geographic location, time of year, and time of day that they desire to fly a particular route. We need to field test the model, refine some of the data layers, expand to areas outside the U.S. and, ultimately, provide near-real time updates to the model using technologies such as doppler radars and satellite telemetry.

Containment basins and bird exclusion--a historical perspective

Most facility engineers with responsibility for hazing birds on containment basins use agricultural crop protection techniques. This approach is appropriate for basins with non-hazardous solutions. Basins containing toxic solutions require an entirely different approach. Detoxification, or exclusion with floating membranes, netting or Bird Balls™ are the best options.

Research and management of bird depredations at catfish farms

Depredations by fish-eating birds are a major constraint on production at commercial catfish facilities in the southeastern United States. A recent survey of catfish farmers estimated total losses due to direct predation by birds and costs associated with employing preventive measures at $17 million, or 4% of national sales. In 1988, the U.S. Department of Agriculture’s (USDA) National Wildlife Research Center (NWRC) established a research station in Mississippi to develop more effective methods for reducing the impact of birds on southeastern aquaculture farms. This paper describes the impact of double-crested cormorant (Phalacrocorax auritus, DCCO) on the catfish industry, describes control methods to reduce depredations by this species, and reviews some research currently being conducted at the NWRC Mississippi research station.

Strategies for alleviating vulture damage in industrial plants

Since 1985, USDA-APHIS-Wildlife Services (WS) personnel have received complaints concerning black vultures (Coragyps atratus) and turkey vultures (Cathartes aura) roosting at industrial facilities along the Texas gulf coast. The structures associated with these facilities are difficult for bird control personnel to access, and remote vulture roosting sites limit the effectiveness of many commonly used bird damage control methods. Methods attempted since 1985 include: capture and relocation, exclusion, harassment and shooting. In 1994, WS entered into a cooperative vulture control agreement with three chemical plants located in southeast Texas. WS personnel have developed an effective vulture damage management strategy that is currently used at six industrial sites in Texas.

The use of aerosol repellents as an avian deterrent strategy

Traditional protective measures to keep wildlife away from areas include exclusion by use of netting, hazing, and chemical repellents. The primary problem with most hazing systems is that wildlife quickly habituate to the devices if their use falls into a predictable pattern. Repellent substances cause wildlife species to avoid otherwise attractive or palatable resources by creating a disincentive to visit a specific area or consume a particular resource. Chemical repellents, both lethal and non-lethal, are typically used for agricultural and horticultural purposes, but in addition may provide a strategy to deter wildlife in other contexts. Aerosol delivery of chemical repellents might work to effectively target birds in the air prior to landing in a hazardous area (i.e., a toxic waste water impoundment). In theory, aerosol delivery of a known avian irritant could be used as an ancillary tool in bird hazing systems, to complement more traditional auditory and visual scare tactics.

Mammalian reservoirs and the changing epidemiology of rabies in the United States

The epidemiology of rabies in the United States has changed dramatically over the past few decades. Greater than 90% of all animal rabies cases reported annually to the Centers for Disease Control and Prevention now occur in wildlife, whereas before 1960 the majority were domestic animals. The principal rabies reservoirs today are wild carnivores and bats, infected with many different types of rabies virus variants. Annual reporting of human deaths have fallen from more than 100 at the turn of the century to one to six per year, despite major outbreaks of animal rabies in several distinct geographic areas. Most recent human rabies cases acquired in the United States are the result of infection with rabies virus variants associated with bats, although the exact incident leading to exposure has been difficult to define. Many recent deaths have occurred in persons who failed to seek post-exposure treatment, presumably because they did not recognize a risk in the animal contact leading to the infection or failed to recognize that contact had occurred. Although these human rabies deaths are rare, estimated public health costs associated with disease detection, prevention, and control have risen, exceeding millions of dollars each year.

Overview of wild pig damage in California

Pigs (Sus scrofa) were first introduced to California in 1769, and European wild boars were imported to Monterey County in 1925. Descendants of the domestic swine and European wild boars have bred and formed populations of wild pigs. By the mid-1960s 15 counties had populations of wild pigs. Today 45 of California’s 58 (78%) counties have reported having populations of pigs. Wild pigs can cause significant damage to farm and rangelands, livestock, natural resources, environmentally sensitive habitats, and property. There are limited estimates of damage caused by wild pigs in California. A survey was sent to all County Agricultural Commissioners in California to document the extent and amount of damage occurring in 1996 and what control measures were taken to reduce the damage. Forty (40) counties responded to the survey and reported $1,731,920 worth of damage caused by wild pigs.

Changes in wild pig depredation in California: a new law

In California, wild pigs occurred in relatively low numbers in 10 to 15 counties until the mid-1960s. Since then, wild pig numbers have increased, and they have expanded their range, primarily in coastal counties from Humboldt to Santa Barbara. Recent surveys indicate that wild pigs occur in at least 47 counties. In California, wild pigs are lawfully defined as game mammals. As such, no part of a wild pig that would normally be eaten by humans can be legally left to waste in the field. In December 1993, the California Fish and Game Commission adopted a new policy for wild pigs. The policy states: "The wild pig population of the state must be controlled to minimize the threat of increasing damage to California’s native plants and animals, to agricultural operations, and to park and recreational activities… [the Department] will recommend to the Commission regulations which enhance recreational hunting and facilitate the issuing of depredation permits and/or other legally available means to alleviate this problem." The new regulation allows the immediate taking of a depredating wild pig by the owner of livestock, land or property, or the owner’s agent or employee, or employee of any federal, state, county or city entity while acting officially. This change greatly expands the number of persons authorized to immediately kill wild pigs which are encountered while in the act of damaging livestock or damaging, destroying, or threatening to immediately damage or destroy land or other property. It also provides for more liberal disposition of the carcass of depredating wild pigs which are immediately killed.

Deer on airports: an accident waiting to happen

The authors analyzed data on civil aircraft strikes with wild ungulates (deer [Odocoileus spp.], elk [Cervus canadensis] and moose [Alces alces]) in the U.S. from the Federal Aviation Administration Wildlife Strike Database and the National Transportation Safety Board Aviation Accident Database for 1983 to 1997. Prior to 1991, the FAA Form 5200-7 for reporting strikes was designated solely for bird strike data, thus, strike reports for non-avian species prior to 1991 are underrepresented. A total of 343 ungulate strikes was reported, 48 from 1983 to 1990 and 295 from 1991 to 1997. Forty-four states reported ungulate strikes with 77% of the reports from states east of the Mississippi River. November had more (P < 0.01) strikes (23%) than any other month. The strike rate (number/hr) was four to nine times greater (P < 0.01) at dusk than at night or dawn. Almost two-thirds of strikes (P < 0.01) occurred during landing, making landing at dusk in November the most likely time for deer strikes. About 79% of strikes had an effect on flight. Aircraft were damaged in 83% of strikes. Only 14% of reports indicating damage provided estimates of cost of repairs. The mean cost for these reports was $74,537. Reported human injuries have been few, but the potential exists for a major disaster. Aircraft with capacity of 101 to 380 passengers were involved in 45 (14%) of the reported strikes. Airports should adopt a "zero tolerance" for deer within the operations area. Deer removal by professional shooters, in conjunction with permanent exclusion with 3 m-high fencing, is the preferred management action.

Potential risks associated with the legalization of exotic predators such as the ferret (Mustela putorius furo) in California

The interest in possessing ferrets as pets has given rise to controversy between the "rights" of the individual to own the pet of their choice and the concerns for protection of wildlife in California. An overview of the legislative history in California illustrates the state’s attempts at protecting native wildlife species from exotic wild birds and animals. Concerns as to the potential threats associated with the legalization of ferrets in California are warranted in light of the wildlife damage resulting from the deliberate introduction of ferrets in New Zealand and the non-native red fox in California. A framework to assess risks involved with introducing non-native species that may impact native wildlife is needed.

Feral goats in Australia: Impacts and cost of control

Feral goats are both a pest and a resource in Australia. They are thought to compete with domestic livestock for food and water and endanger the survival of native flora and fauna. However, there is little quantitative information on the impact of feral goats on agricultural production or conservation values. Their presence on agricultural land is partly tolerated since they can be commercially harvested by mustering or trapping at water points. Where commercial harvesting is not possible, other control techniques must be used. Aerial shooting is the most commonly used technique to remove goats in inaccessible areas, but it is expensive. This paper reviews the status and impacts of feral goats in Australia. It then outlines some cost of control models that predict the cost of controlling goats at different densities using aerial shooting in inaccessible terrain in the semi-arid rangelands of Australia.

Evaluation of electronic frightening devices as white-tailed deer deterrents

The authors evaluated the effectiveness of the motion-activated Usonic Sentry (with and without strobe), motion-activated Yard Gard, and Electronic Guard for deterring white-tailed deer (Odocoileus virginianus) from preferred feeding areas from February to April 1996. Two four-week experiments were conducted, monitoring deer use (number of intrusions and com consumption) at eight feeding stations in a 2,200-ha fenced facility in northern Ohio with high deer densities (≥38/km2). During these experiments, one of the devices was positioned at each of four sites. The mean(± SE, n = 4) daily number of deer intrusions at feeding stations during treatment (96.5 ± 12.6-169.0 ± 22.0) was similar (P ≥ 0.13) to or greater (P 0.04) than the mean daily number of deer intrusions during pre- or post-treatment (109.8 ± 15.6-148.8 ± 21.4). Corn consumption declined (P ≤ 0.05) only at stations with Usonic Sentrys without strobes for one week. It was concluded that the electronic frightening devices tested were generally ineffective in deterring white-tailed deer from preferred feeding areas.

The impact of timber management on the phytochemicals associated with black bear damage

Black bears forage on Douglas-fir vascular tissue in the spring, and this behavior can be severely detrimental to the health and economic value of a timber stand. Foraging is selective in that not all stands are damaged and, within a stand, one tree may be stripped while its neighbor is ignored or minimally sampled. A series of studies was conducted to assess whether bear selectivity is affected by chemical constituents within vascular tissue, and whether these constituents are affected by silvicultural practices. The results are interpreted to identify forest practices that may alleviate damage, or at least predict where damage is most likely to occur.

Trends in mountain lion depredation and public safety incidents in California

Mountain lions (Puma concolor) are widely distributed and have apparently expanded their range and increased in abundance in California since the early 1970s. Conflicts between mountain lions and humans have increased during this period. Trends in verified mountain lion damage to livestock and pets are reported for the 26-year period 1972 to 1997. Confirmed mountain lion attacks on humans are summarized for the period 1890 to 1997. This information was analyzed by county, and related to mountain lion habitat suitability, livestock distribution, and human population trends. Health and physical characteristics of a sample of 417 mountain lions were also analyzed for the period 1990 to 1996. Public policy related to mountain lions is discussed with emphasis on trends in conflicts with humans and management implications.

North Dakota's cost-share program for guard animals

Beginning in July 1991, the North Dakota Game and Fish Department authorized the use of funds in a cost-share program to assist farmers and ranchers with the implementation of nonlethal methods to protect livestock. Fund expenditures are administered and approved by the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, North Dakota program. The program provides a 50:50 cost-share up to a maximum of $150 per purchase of nonlethal items for the protection of livestock from predation. During the six year period from July 1991 to July 1997, the program has cost-shared dogs, donkeys, electronic guards, and llamas. The Great Pyrenees dog breed was the method most frequently selected.

Non-lethal predation control by U.S. sheep ranchers

The USDA National Agricultural Statistics Service (NASS) surveyed U.S. sheep producers to determine the kinds of non-lethal (NL) predator control measures they used in 1994. An analysis of responses from 8,451 sheep producers showed that 34% of the nation’s sheep producers used fencing, 25% used husbandry, 20% used guard animals, 4% used frightening tactics, 0.3% used aversion, and 3% used other methods. Because NL methods tended to be used more in large sheep operations than on small farms, the percentages of sheep protected by each NL control method were higher than the percentages of sheep producers using the method. Approximately 33% of all sheep in the U.S. were protected by fencing, 40% by husbandry, 39% by guard animals, 12% by frightening tactics, 2% by aversion, and 5% by other methods. Overall, 55% of U.S. sheep producers used one or more NL predator control methods in 1974, and 70% of the nation’s sheep were protected by one or more NL methods.

Amendment 14--Colorado's anti-trapping initiative, a history and perspective on impacts

In November 1996, Colorado voters approved constitutional Amendment 14, an anti-trapping initiative, which prohibited the taking of wildlife with any leghold trap, any instant kill body-gripping design trap, or by poison or snare. Several exemptions were provided. This paper summarizes the history of events leading up to the introduction of the Amendment, and examines some of the initial impacts on the federal Wildlife Services program, the sheep industry, and the people of Colorado.

Managing island biotas: brown tree snake control using barrier technology

The brown treesnake (Boiga irregularis), accidently introduced to the previously snake-free U.S. island of Guam after World War II, decimated the island’s naive wildlife. Today, it periodically stows away on craft going to other islands where the ecological damage may be repeated. Barriers offer an effective tool for keeping the snakes out of areas from which they can disperse off-island, as well as sites identified as critical for the protection of human health, conduct of economic activity, or conservation of endangered species. The authors have developed a variety of barrier designs which repulse at least 95% of snake attempts to scale them under laboratory conditions; the best performing models are 100% effective. Three of the designs are in operational use. Designs for maximizing snake repulsion will be more costly to build, but may have lower annual costs due to reduced expenses for system upkeep.

Fertility control in coyotes: Is it a potential management tool?

Fertility control in wildlife is emerging as a potential management tool. Published research on feral horses, deer, rodents, and rabbits suggest an effective agent producing reversible infertility in these species could be developed. Furthermore, anecdotal reports suggest that infertility can be induced in a greater array of species. In this paper, the authors review methods of fertility control being studied for application in wildlife and focus on their studies designed to evaluate the effectiveness of fertility control agents in coyotes (Canis latrans). Immunocontraception using porcine zona pellucida (PZP) is currently the most promising method of fertility control in coyotes the authors have studied. This is consistent with results from other species. However, the vital question of whether any fertility control agent can reduce livestock losses due to coyote predation will require more research.

Social and biological aspects of non-native red fox management in California

Since the late 1800s, non-native red foxes have been introduced in California for fur farming and fox hunting. Dispersal, population growth, and extensive translocations by humans have aided the expansion of the nonnative fox population throughout many of the lowland and coastal areas of the state. Since the 1980s, non-native red foxes have been recognized as predators of a number of endangered species. Trapping and euthanizing non-native red foxes have been used as methods to protect these endangered species, but have been opposed by some members of the public. Opposition by animal rights groups to red fox trapping and euthanization has significantly influenced the management actions and policies of wildlife agencies. Red foxes are among the wildlife species commonly recognized in our culture; however, their historical use as a commodity and a game animal, and their impact on several endangered species, make them a difficult and controversial species to manage. Both fox biology and the public place great demands on wildlife agencies to develop new, proactive management strategies for non-native red foxes.

The management of house mice in agricultural landscapes using farm management practices: an Australian perspective

During 1995 to 1997, the efficacy of early tactical management of mouse populations in a project based on grain-growing farms in Victoria, Australia was examined. Farmers modified their management practices of crops (at sowing, harvest, and land preparation), and managed habitats on the boundary of cropped land (such as fencelines) and around farm buildings. One management practice examined was the effect on mouse populations of controlling weeds along margins of crops. On sites where farmers slashed or sprayed weeds in early spring, there was a comparative reduction in the abundance of mice in late summer compared to untreated sites.

Managing mouse plagues in rural Australia

The frequency of mouse plagues in grain-growing areas of Australia has increased since the advent of conservation farming practices. The increase has been particularly marked on the Darling Downs in Queensland where the frequency has trebled. Broad-scale monitoring is undertaken by the government to provide a general forewarning of plague. However, the authors found, from a questionnaire to farmers, that the incidence and timing of plagues is highly variable across the Downs. It is apparent that farmers need to monitor the numbers of mice on their properties at regular intervals if they are to undertake preventive management. Bait cards (pieces of paper soaked in canola oil) were tested as a method for on-farm monitoring. The average amount of each card eaten was significantly correlated with the density of mice, but because of the scatter of the data the authors recommend that the cards be used in conjunction with other signs of mice such as evidence of crop damage or of active holes and runways in stubble. Zinc phosphide bait was found to be a highly effective rodenticide if used at a time when food was scarce. If the bait receives registration, it would be a valuable tool to control mice in crops, especially prior to flowering. On the basis of these results, it was concluded that effective management of mice could best be achieved by minimizing food supply in stubble by efficient harvesting, regular monitoring, and by strategic baiting and stubble management when necessary.

An overview of recent ground squirrel bait registration research supported by the California bait surcharge program

The California Department of Food and Agriculture Rodent Bait Surcharge Program is actively funding studies to develop and register safe, effective and practical ground squirrel baits. Under this program, Genesis Laboratories has conducted eight studies since 1994 designed to fulfill registration requirements for existing baits and to develop new baits. Areas of research include field efficacy, application methods and rates, non-target hazards, and residue loads in animal and plant tissues. Existing diphacinone and chlorophacinone treated oat groat baits have proven to be effective in controlling the California ground squirrel. Applications of these baits to alfalfa crops did not result in quantifiable residue loads. Preliminary studies found bromethalin treated oats may be effective against the California ground squirrel. Chlorophacinone treated cabbage bait was not effective against Belding’s ground squirrel.

The development of an integrated pest management plan for roof rats in Hawaiian macadamia orchards

Roof rats (Rattus rattus) damage an estimated 5 to 10% of the developing nut crop in Hawaiian macadamia (Macadamia integrifolia) orchards. Relevant aspects of roof rat biology in macadamia orchards have and continue to be studied with the ultimate goal of developing an ecologically sound and cost-effective integrated pest management plan. The field component of a two-year study of roof rat populations in macadamia orchards has recently been completed. The goal of this study is to clarify the relationship between roof rat seasonal abundance, macadamia flowering, and nut production on five orchards in three regions on the island of Hawaii. The authors herein present preliminary results from selected aspects of this research. This and other completed studies on rat feeding locations and the effect of simulated rat damage during different stages of nut development will aid in the determination of critical points in the crop cycle when rats cause significant economic damage and control of damage is warranted. This paper is intended to be an overview of research leading to the development of a realistic integrated pest management plan for roof rats in Hawaiian macadamia orchards.

The bait surcharge program: research improves zinc phosphide use for vole control in alfalfa

This paper describes several unexpected benefits of rodenticide-registration research funded by the California Bait Surcharge Program. An enclosure-type study was conducted to determine efficacy of single, pre- and test-bait broadcasts (10 lb./ac.) of 0% and 2% zinc phosphide (Zn3P2, CAS #1314-84-7) steam-rolled-oat (SRO) groats to control voles (Microtus spp.) in alfalfa (Medicago sativa). Unexpected research spinoffs resulted from the use of: 1) eight randomly-located, sieved-dirt plots per enclosure to monitor bait distribution, bait removal, and rodent/avian (non-target) activity; 2) a bait-weathering plot and bait-sample analyses to monitor Zn3P2 biodeterioration; and 3) a C++- language program to derive theoretical benefit-cost ratios associated with Zn3P2-bait broadcasts

A survey of rabbit damage and control measures used in the east and northeast of Scotland

A postal survey conducted of 172 farms in the intensive fanning areas of East and Northeast Scotland revealed that one in four farms considered that there was a serious rabbit (Oryctolagus cuniculus L.) problem. Although a wide range of crops was subject to damage, winter cereals and winter oilseed rape were particularly affected by grazing, especially in the winter and spring periods. Two-thirds of farmers reported damage to temporary and permanent grass in the spring. The most common methods used to control rabbit damage were day-time and night-time shooting. Most methods of control were considered to be cost and time effective.

Laboratory efficacy study with a warfarin bait to control the black-tailed prairie dog

Control of the black-tailed prairie dog (Cynomys ludovicianus) is important for the reclamation of pasture ground for domestic cattle and limiting the spread of disease to humans and other wildlife. Six different concentrations of warfarin bait were fed to prairie dogs to determine mortality. Without the access to dietary vitamin K, the prairie dogs were susceptible to the warfarin bait. However, some of the prairie dogs recovered and survived the test after bait exposure was terminated. This could be due to physiological differences and the availability of fat-soluble vitamin K. The six different concentrations of warfarin consumed by the prairie dogs were correlated to the increase in treatment group (r=0.916). Body weight loss generally increased as the treatment group dosage increased. The control group was the only group which increased in body weight. The whole body tissue analysis of the prairie dogs from treatment groups 44.8, 233.0, and 777.6 ppm was correlated to the increase in treatment group (r=0.709).

Effects of taste stimuli (quinine and sucrose) in pelleted, granulated, and wax block baits on feeding preferences of northern pocket gophers (Thomomys talpoides)

A two-choice, taste preference study was conducted using 18 northern pocket gophers to evaluate pelleted sorghum, granulated sorghum, and wax block baits containing either 0.01 to 0.05% quinine or 0.10 to 5.0% sucrose. Bait consumption was significantly higher across treatments (P ≤ .001) for granulated sorghum, followed by pelleted sorghum, and wax blocks. Gophers also showed a high frequency of moving the granulated bait in their cheek pouches to be deposited at alternate locations within their cages. Although increasing sucrose concentration did not produce significantly (P ≥ .10) enhanced consumption for any of the baits, a trend toward increasing preference with increased concentration was noted for the wax block bait. During quinine tests, bait consumption was again significantly highest (P ≤ .01) for granulated sorghum followed by pelleted sorghum and wax block. Quinine treatment also failed to significantly (P ≥ .10) alter bait consumption across the tested concentrations. However, there was a minor trend toward decreasing preference with increasing concentrations in the wax block group. Data indicated that pelleted bait had the advantage of producing more consistent consumption levels without the animals carrying bait in their cheek pouches for caching and subsequent spillage. Although the wax block baits were most influenced by the taste treatments, consumption levels were extremely low. In comparison with most wild rodent species, northern pocket gophers were found to be insensitive or indifferent to both taste stimuli over a wide concentration range.

Management of red squirrel feeding damage to Lodgepole Pine by stand density manipulation and diversionary food

The red squirrel (Tamiasciurus hudsonicus) feeds on the vascular tissues of sapling lodgepole pine (Pinus contorta) during spring periods in forests of interior British Columbia and Alberta, Canada. This damage may lead to mortality and reduced growth of crop trees in managed stands. Manipulation of stand density by pre-commercial thinning to densities < 1,000 stems/ha is an effective method to lower squirrel populations and feeding damage. Lowering stand density enhances the growth of crop trees, and understory herbs and shrubs as wildlife habitat, while protecting trees from squirrel feeding. This approach has been successful in several forest ecological zones. An alternative management tool is provision of diversionary food (sunflower seed) for those stands susceptible to feeding damage, and where stand thinning bas already been completed. Diversionary food can be applied aerially and is very cost effective for protecting managed stands. These techniques may be used to maintain or even enhance species diversity of small mammal communities in those forest stands requiring protection.

Porcupine damage and repellent research in the interior Pacific Northwest

Porcupines (Erethizon dorsatum) rely on trees and shrubs for winter food and can cause serious, localized damage to conifers. Twenty-two percent of ponderosa trees (Pinus ponderosa) examined in southeastern Washington were damaged by porcupines. Most damage involved complete girdling of the mid- to upper boles of the larger trees (12 to 30 cm dbh) in the stand. Preliminary repellent trials with captive porcupines suggested that several materials might reduce tree damage, especially predator-associated odors. Field trials are needed to assess efficacy and duration of protection under ambient winter conditions.

Surveillance for Sin Nombre virus and hantavirus pulmonary syndrome in California, 1993 to 1997

Hantavirus Pulmonary Syndrome (HPS), a severe and frequently fatal respiratory disease, was first recognized in 1993 during an outbreak of acute illness in the Four Comers area of the southwestern United States. The etiologic agent, Sin Nombre virus (SNV), was identified as a previously unrecognized member of the Hantavirus genus transmitted by rodents, especially members of the genus Peromyscus, which shed SNV in urine and feces. Since 1993, 16 California residents have been diagnosed with HPS, four of these were identified retrospectively with onset prior to 1993. The median age of case-patients was 42 years, 10 were male, and 8 died. Sites of likely exposure for these cases tended to cluster in the eastern Sierra Nevada range. Serologic surveillance of rodents has been conducted prospectively in California since 1993 and retrospectively for specimens collected back to 1975. To date, serologic evidence of infection with SNV has been recognized in 473 (6.6%) of 7,191 rodents from 18 genera, and in 426 (9.6%) of 4,489 Peromyscus spp. At least one seroreactive Peromyscus sp. specimen has been identified in 40 of 46 counties surveyed.

Will continued monitoring of beaver-damaged resources minimize future damage?

The purpose of this study was to determine if continued monitoring and removal of beavers (Castor canadensis) from previously controlled beaver damage sites resulted in less additional damage than not monitoring such sites. Beavers were removed from 34 sites in nine southeast Texas counties from August 1996 through March 1997. Sixteen sites subsequently were monitored monthly and, if beavers had reinvaded, they were removed and the additional damage value was recorded. The remaining 18 sites were not monitored monthly, but they were visited for a final survey at the end of the study. The value of additional damage was recorded at that time. Damage following reinvasion occurred more often when sites were not monitored (5 of 7 sites, compared to only 2 of 7 reinvaded, monitored sites). In addition, when damage occurred at reinvaded sites, monetary value appeared to be greater without monitoring (average $940, n=5) than with monitoring (average $125, n=2). The larger average damage values for reinvaded unmonitored sites compared to reinvaded monitored sites would be important to landowners when deciding if property should be monitored. Factors that made some sites susceptible to reinvasion were also evaluated. Significantly more beavers were taken initially, per site, in the reinvaded sites compared to all other sites. This implies that better habitat and higher beaver density were the most important factors in determining a site’s susceptibility to reinvasion.

One hundred years of pocker gopher traps and trapping

The pest status of pocket gophers (Thomomys spp. and Geomys spp.) to agricultural crops and home gardens is well established, as is the fact that trapping in the early history of this country and its western expansion was the predominant method of their control. The former payment of bounties for gopher scalps or tails is thought to have stimulated the development and production of dozens of different kinds and models of gopher traps. In the Midwest, prior to the industrial revolution, small size leg-hold traps were used for taking gophers because they were the only traps available. By 1880, traps were being developed and manufactured specifically for gophers, with a dozen or so marketed prior to 1900. The zenith of gopher trap development was from 1900 through the 1930s. Following the end of World War II, the use of poison baits for gopher control significantly replaced the use of traps. Five of the most successful gopher traps, all with a long history of production, are enumerated and the specific history of the Macabee gopher trap is detailed.

Evaluation of acrolein as a fumigant for controlling northern pocket gophers

Baker Performance Chemical Incorporated entered into a cooperative agreement with the National Wildlife Research Center to evaluate acrolein as a fumigant for controlling northern pocket gophers (Thomomys talpoides). In October 1996, a 44.5 ha (110 acre) irrigated alfalfa hay field was selected as the study site in Franklin County, Washington. Eight treatment units (TUs), six fumigated, and two control, were established on the study site. On the six fumigated TUs, 58.9% of the sample plots were inactive, whereas, all sample plots (100%) on the two control TUs were active. The 58.9% mean reduction in pocket gopher activity on the six fumigated TUs was below the minimum efficacy standard of 70% established by the Environmental Protection Agency (EPA 1982). Possible reasons for the pocket gophers surviving the acrolein treatment are discussed.

Modified bait stations for California ground squirrel control in engangered kangaroo rat habitat

California ground squirrels are a major problem in areas that also support populations of endangered kangaroo rats. Traditional bait stations can be easily modified to exclude kangaroo rats, thereby providing landowners with a method of controlling ground squirrels that mitigates hazards to endangered kangaroo rats. Specifications for the design and use of modified bait stations are discussed.

Not all sigmodontine rodents in the sugarcane fields in coastal Veracruz, Mexico, are pests

Rats and mice have traditionally been considered one of the most important pests of sugarcane. However, "control" campaigns are rarely specific to the target species, and can have an effect on local wildlife, in particular non-pest rodent species. The objective of this study was to distinguish between rodent species that are pests and those that are not, and to identify patterns of food utilization by the rodents in the sugarcane crop complex. Within the crop complex, subsistence crops like maize, sorghum, rice, and bananas, which are grown alongside the sugarcane, are also subject to rodent damage. Six native rodent species were trapped in the Papaloapan River Basin of the State of Veracruz; the cotton rat (Sigmodon hispidus), the rice rate (Oryzomys couesi), the small rice rat (O. chapmani), the white footed mouse (Peromyscus leucopus), the golden mouse (Reithrodomomys sumichrasti), and the pigmy mouse (Baiomys musculus). In a stomach content analysis, the major food components for the cotton rat, the rice rat and the small rice rat were sugarcane (4.9 to 30.1%), seed (2.7 to 22.9%), and vegetation (0.9 to 29.8%); while for the golden mouse and the pigmy mouse the stomach content was almost exclusively seed (98 to 100%). The authors consider the first three species to be pests of the sugarcane crop complex, while the last two species are not.

Norway rat exclusion in Alberta

Since 1950, Alberta Agriculture has supervised and coordinated a rural-based Norway rat (Rattus norvegicus) control program that has essentially kept the province rat-free. Success is achieved by eliminating invading rats within a control zone 600 km long and 30 km wide along the eastern border of the province. A systematic detection and eradication system is used throughout the zone to keep rat infestations to a minimum. Strong public support and citizen participation was developed through public education and a sound awareness effort. Although rat infestations within the interior are minor, a rat response plan is in place to deal with a large or difficult case. Government preparedness, legislation, climate, geography, effective rat baits and close cooperation between provincial and municipal governments have contributed to program success.

Control of Norway rats in sewer and utility systems using pulsed baiting methods

There were 1,288 sewer and 235 other utility manholes baited to control Norway rat (Rattus norvegicus) populations in downtown Boston using pulsed-baiting methods. About 15% of all sewer, 18% of phone, and 26% of electric manholes had rat activity. Sewer populations were most associated with residential areas with low flow, small diameter (<61 cm) brick sewers; in those circumstances, up to 38% of manholes had rat activity. Bait consumption in sewers (high risk areas) was 91% below baseline, five months after the fourth baiting period. Bait consumption and the number of active sewer holes were 96% and 87% below baseline, respectively, when seasonal maintenance baiting was last initiated. Reinfestation of phone/electric manholes was so minimal that maintenance baiting was not necessary or cost-effective. Subsurface baiting should be an integral part of urban rodent control programs.

Recent Norway rats studies using warfarin

Warfarin resistance in the Norway rat (Rattus norvegicus) has been studied over the past 30 years. To determine the status of this resistance phenomenon wild Norway rats were collected from Colorado and Chicago, Illinois. As reported previously, warfarin resistance in the Chicago area exceeds 50%, while rats from Colorado remain very susceptible to warfarin. The theory that true genetic resistance may not exist was examined, implying that geographic variation in intestinal flora contribute to the rapid degradation of warfarin after ingestion, along with production of sufficient Vitamin K in the bacteria to reverse the effect of warfarin. Antibiotics in combination were tested with warfarin and demonstrated that efficacy in the laboratory can be increased by using the combination in a bait form.

Control of rats resistant to second-generation anticoagulant rodenticides

Second-generation anticoagulant rodenticides were introduced to control Norway rats that had become resistant to first-generation compounds. Unfortunately, some rats have become resistant to these as well. The lack of alternative rodenticides with the same attributes of ease of use and relative safety is potentially a serious problem should resistance become so widespread that anticoagulants are no longer effective. However, the second-generation anticoagulants difenacoum and bromadiolone can still be effective provided most rats in a population possess only a low degree of resistance to them. Measures that maximize the uptake of bait, such as using the most palatable formulation, baiting burrows and saturation baiting have to be implemented. The low levels of resistance discovered so far mean that the most potent anticoagulants, such as brodifacoum and flocoumafen, should also control most populations if baits containing either of them are properly applied. These two rodenticides are restricted to indoor use in the United Kingdom and are thus not available to control those rats living outdoors that are highly resistant to all other anticoagulants. Those rats can, however, be controlled with either zinc phosphide or calciferol, preferably after prebaiting. Strategies to manage resistance in the long-term should be implemented before high-degree resistance spreads. One potential tactic is to stop using anticoagulants altogether and allow deleterious pleiotropic effects to reduce the prevalence of resistance in a population. Any attempts to manager resistance are only relevant if the intention is to retain anticoagulant rodenticides, with their undoubted advantages, as the main method of controlling rodent pests.

The efficacy of glue traps against wild populations of house mice, Mus domesticus Rutty

Field research was conducted from Purdue University during 1991 to 1993 to examine some aspects of the efficaciousness of the various types of glue traps against wild populations of house mice. The research was conducted in agricultural and livestock buildings containing various infestation levels of mice. Tests compared the capture and escape rates of glue boards vs. trays, covered vs. uncovered glue traps, and glue traps vs. snap traps, and multiple catch curiosity traps. Observational work, via night vigils, was also conducted to note the behavioral response of mice to glue surfaces, including the behavioral aspects of mice neutralizing glue surfaces in well-used runways. These field tests indicate many mice, upon initial interactions with glue traps and surfaces, are repelled by them and either learn to avoid them or neutralized them in some manner. Results of comparison trials between glue traps and non-glue mouse traps also indicate strong differences in interaction and capture rates favoring non-glue traps. It is hypothesized that when glue traps are successful, it is likely due to mice traveling kinesthetically along frequently used runways in which traps are placed, or to factors associated with age class of mice. These studies have strong implications for rodent pest management programs in facilities which are restricted to non-chemical approaches (e.g., food handling establishments and sensitive accounts).

Warfarin resistance revisited

Roughly 50 years ago, the Wisconsin Alumni Research Foundation developed warfarin, the first anticoagulant rodenticide. This product was something close to that desired elusive "magic bullet" of pest management. Warfarin effectively killed rats and mice, required multiple feedings, and had a good margin of safety for non-target species. The widespread adoption of anticoagulants somewhat changed the conduct of rodent control with a shift in interventions toward toxicants and away from education and physical measures. The discovery of warfarin resistance in the United States in Rattus norvegicus in 1971, and later in Mus musculus and Rattus rattus, heralded in another shift in rodent pest mitigation. This shift was the development of more toxic anticoagulant products capable of killing with one or a few feedings and with concomitantly greater risks to non-target species. Development of the more toxic products both anticoagulant and non-anticoagulant continues today, although there is an increasing trend favoring comprehensive approaches (i.e., integrated pest management [IPM]) which: emphasize educating clients and reducing causative conditions; diminishing the role of toxicants; and, when necessary, using products of the least practical toxicity. In this paper, the concept of counteracting anticoagulant resistance is blended with the sometimes necessary use of anticoagulant rodenticides as part of IPM. Nationwide data from the former New York State Department of Health Rodent Control Evaluation Laboratory (in cooperation with the Centers for Disease Control’s former Urban Rat Control Program) are examined regarding warfarin resistance in Rattus norvegicus. In samples from two dozen project cities, population resistance levels ranged from 1.6% to 76.2% using the standard World Health Organization (WHO) testing criteria. However, most survivors (i.e., resistant rats) of the initial test succumbed upon one or more re-exposure(s) to warfarin using the same WHO testing protocol. The results are surprising and have implications on interpreting the phenomenon of anticoagulant rodenticide resistance and on the pragmatic designing of rodent management programs.

Rat management for endangered species protection in the U.S. Virgin Islands

Introduced roof rats (Rattus rattus) pose a substantial threat to the fauna and flora of many tropical islands. In the Caribbean, there is concern about rat impacts to several endangered species, including the Atlantic hawksbill sea turtle (Eretmochelys imbricata) and the least tern (Sterna antillarum). The authors surveyed the rat population on Buck Island, Buck Island Reef National Monument, U.S. Virgin Islands in February 1998. Based on three nights of trapping, rats were of low to moderate abundance during the sampling period when compared to results from other Caribbean islands. The impact of rats on native vegetation was evident over the entire island. A rat management program was proposed using anticoagulant rodenticide baits in bait boxes in and around the two picnic areas on the island. Once an appropriate rodenticide registration is obtained, the baiting program can be extended to include the rest of the island. The eventual eradication of rats from Buck Island will not only provide relief for several endangered species nesting on the island, but will set the stage for the reintroduction of the endangered St. Croix ground lizard (Ameiva polops).

State agency response to nuisance wildlife control operator oversight

An 18-question survey was sent to all state wildlife agency directors in an attempt to evaluate state wildlife agencies’ response to administrative oversight of nuisance wildlife control operators (NWCO). Forty-four (88%) of the state wildlife agencies responded to the survey. Almost every state agency responding believes they should promote the growth and privatization of the NWCO industry. They also believe that their agency should provide administrative oversight. There were descrepancies in what agency personnel believe constitute oversight versus what policies are actually implemented. Although most agencies believe NWCO should be licensed, only 56% of states actually require licensing. Most agencies responding believe NWCO should be required to complete an educational program and a written examination prior to receiving a license, currently only 22% require some form of education prior to obtaining a license, and 15% require an examination prior to obtaining a license. Sixty percent of agencies believe NWCO should show evidence of financial responsibility and only 5% of states actually require NWCO to have liability insurance or post a surety bond. Fifty-six percent of the states require NWCO to submit written reports that document the number of each animal species captured (51%), disposition of animals (44%), location of capture animals (34%), release site information (22%), condition of captured animal (7%), and euthanization method (5%). Most states allow nuisance wildlife to be released on both private (90%) and public land (71%). Approximately one-third of agencies have changed laws, policies, or regulations regarding NWCO and 47% of these changes are perceived to be more restrictive of NWCO activities. Most state agencies (78%) allow relocation of nuisance wildlife, but 17% of the states have restrictions on what species can be relocated. The primary reason for not allowing relocation of nuisance wildlife are disease (100%), impacts to resident wildlife populations (45%), humane reasons (18%), and a lack of suitable release sites (9%). These results show that state agencies believe they should encourage the growth and privatization of NWCO industry and that they should maintain administrative oversight.

Defensible space: a behavioral approach for managing predators at the urban-wildland interface

Southern California bas experienced rapid human population growth during the past 50 years. As housing continues to encroach into and abut previously undeveloped areas containing wildlife communities, conflicts between homeowners and predators have become common. Traditional methods of control (removal) of problem animals are often infeasible due to legislative constraints, local ordinances, public opinion, and environmental considerations. This necessitates developing alternative approaches to facilitate coexistence and diminish the opportunities for negative interactions. In the Defensible Space program, people are educated about local wildlife and provided animal behavior-based methods to respond to animal incursions. Though the system is not always 100% effective, it has diminished the overall number of complaints received and reduced most of the remaining complaints from panic-based to knowledge-based.

Ecology and management of coyotes in Tucson, Arizona

Increasingly, coyotes are becoming common residents of urban areas in the western United States, including Tucson, Arizona. The authors’ objectives were to determine the home-range size of coyotes in Tucson, the habitat encompassed by the home ranges of these coyotes compared with the habitat available in Tucson, and the use of habitats within the home range, compared to their availability in the home range. To address these objectives, the authors trapped, radiocollared, and followed 13 coyotes via radiotelemetry in Tucson, Arizona. Seven coyotes were in less-densely populated areas (<1 house/0.4 ha, called rural) of Tucson; six coyotes were in densely populated areas (>1 house/0.4 ha, called urban) of Tucson. The authors used RANGES V to determine home-range size and the geographic information system ARC/INFO to analyze habitat use. The home-range size of Tucson coyotes varied from 129 to 3,279 ha (95% MCP). Coyote home ranges in rural areas included a greater proportion of natural habitat and a smaller proportion of residential habitat than was available in the study area. Coyote home ranges in urban areas included a greater proportion of vacant areas and a smaller proportion of natural areas and parks than was available in the study area. Within the home range, coyotes in rural areas preferred (used greater than available) parks and washes, and avoided (used less than available) all other habitats. Within the home range, coyotes in urban areas preferred residential habitat; they avoided commercial areas and vacant areas. Coyotes may have been preferring areas where food and cover was most abundant.

Management of conflicts between urban coyotes and humans in Southern California

An apparent increase in coyote-human conflicts, notably attacks on humans, demonstrates that such incidents are not rare in California. The authors discuss coyote attacks on 53 humans, resulting in 21 instances of human injury, over the last decade. These illustrate repeated, predictable pre-attack coyote behavior patterns. Specific changes in human environments and in human behavior that have contributed to coyote attacks are discussed. Case histories of attacks reveal contributing factors and suggest appropriate corrective and preventive actions. Padded leghold traps have been the most effective and efficient tool in removing problem coyotes and changing the behavior of coyotes to fear humans and the urban environment. Long-term solutions will require changes in human behavior. Humans must come to view large mammalian predators as a potential hazard. Increased public education is needed to improve methods of landscape management, refuse disposal, care of pets, and recognition of the need for predator management.

A techniques manual and video for the management of problem urban Canada geese

Social and management problems associated with urban Canada geese (Branta canadensis) are increasing in area, scope and magnitude. Although there are many articles on the management of urban Canada geese, none provide enough information for a reader to understand the impact geese have on different people, the ecology of the urban goose, evaluate the effectiveness of potential control options, choose appropriate management techniques, and then implement the chosen techniques. The authors present a manual and video, which in combination, they believe are not deficient in any of these areas. The video is intended to increase the awareness and knowledge of human/goose conflicts in urban and suburban environments. The manual covers the biology of Canada geese relevant to problem management in an urban setting and a comprehensive list of management techniques. Detailed instructions for implementation, permit requirements, sources of equipment and supplies, and a discussion of advantages, disadvantages, and characteristics, are included for each technique. To assist in choosing and locating appropriate techniques, quick reference summary tables are included.

Twenty-five years of managing birds associated with buildings at the University of California, Berkeley

Information concerning 19 species of birds associated with 28 buildings on the University of California at Berkeley campus has been collected for 25 years. Sixteen species are included under three minor associations (temporary roosters, building invaders, and species that nest on (or in) buildings in small numbers). Barn owls and ravens have caused intense, though localized problems. Two additional species (cliff swallows and feral pigeons) have caused major problems. Feral pigeons have caused the most difficult problems to resolve. Case histories are used to describe problems associated with these birds, and control strategies for them. Cooper’s hawks have nested in central campus locations for the last four years and their contributions to pigeon control, interactions with campus buildings, and adjustments to their presence are discussed.

Status of APHIS vertebrate pesticides and drugs

The Wildlife Services (WS) Program manages wildlife/human conflicts by using an integrated approach employing some vertebrate pesticides. These are used in such small quantities that private industry cannot afford to register and produce them profitably. On behalf of WS, the Animal and Plant Health Inspection Service (APHIS) maintains about 30 federal and state pesticide registrations, containing seven active ingredients, with the U.S. Environmental Protection Agency (EPA). These include: the Compound 1080 Livestock Protection Collar, DRC-1339 Concentrates (Starlicide), Gas Cartridges (carbon and sodium nitrate), the M-44 (sodium cyanide), and a number of baits and concentrates containing Strychnine Alkaloid and Zinc Phosphide. In 1988 Congress amended the Federal Insecticide, Fungicide, and Rodenticide Act, requiring reregistration of almost all older pesticides. Reregistration had an extensive impact on the WS Program. Over 400 studies, with an estimated cost of about $14 million, were requested by EPA for APHIS products. Through negotiations with EPA, repackaging of old data, and obtaining data waivers for inappropriate studies, National Wildlife Research Center (NWRC) and APHIS personnel reduced the data requirements to about 250 studies costing $3 million. In addition, the NWRC managed three Consortia that generated funds and data to maintain Starlicide, strychnine and zinc phosphide products held by APHIS, private industry, and state agencies. APHIS is now entering the fmal stages of reregistration. Carbon, sodium nitrate, sodium cyanide, Compound 1080, and Starlicide have been reregistered. The Reregistration Eligibility Decision (RED), with an appended product-specific data call-in notice, was received for strychnine in March 1997 and the remaining data are being generated. Reregistration of zinc phosphide is expected sometime in 1998. In addition, APHIS now maintains four products for the WS Program with the U.S. Food and Drug Administration (FDA) under Investigational New Animal Drug (INAD) permits. These include alpha-chloralose (a capturing agent), the Tranquilizer Trap Device (TTD) containing propiopromazine HCl (to sedate animals held in leghold traps and snares), and two immunocontraceptive vaccines, porcine zona pellucida (Zonacon), and gonadotrophin releasing hormone (Gonacon) for contracepting deer and other wild animals.

Mammal repellents: options and considerations for development

Repellents include chemical substances, visual displays, and sonic and ultrasonic deterrent systems. The use of electric shock also can be considered as a repellent category. Each of these categories is discussed, together with their respective utilities, constraints on their usefulness, and possibilities for future development. Economic considerations that may impede or expedite the development of new strategies are presented. Repellent effectiveness depends upon a complex of variables, including the palatability of protected and alternative foods, weather conditions, and the number of animals causing problems. Invariably, repellents are most useful when used as components of integrated pest management strategies.

Review of bird repellents

Despite a general perception that there is an abundance of nonlethal control technologies, the fact remains that there are fewer registered products and active ingredients for repellents in the U.S. than there were 10 and 20 years ago. This review discusses the technical issues relating to the discovery, formulation, and delivery of chemical repellents, and suggests future avenues of research that would improve our ability to develop effective chemical repellents.

Development of a new bird repellent, Flight Control

In August 1995 the development of a new bird repellent, Flight Control containing anthraquinone, was initiated. A series of laboratory formulation testing, cage and pen studies were conducted. The anthraquinone discrimination threshold (concentration at which birds could detect the test material) for starlings (Sturnus vulgaris) was 151 ppm in treated feeds. The model revealed that to achieve 90% repellency with Flight Control, the treated material should receive 1,131 ppm of anthraquinone. Bird feed containing pesticide granules treated with 1% anthraquinone and control feed in a lab choice study, resulted in zero mortality in quail chicks (Colinus virginianus). Pen studies with American robins (Turdus migratorius) demonstrated Flight Control repelled the species when holly berries were treated with 500 ppm anthraquinone. Pen studies in Louisiana using Flight Control-treated rice seeds generated efficacy in excess of 90% to cowbirds (Molothrus ater) and red-winged blackbirds (Agelaius phoeniceus).

Field trial using Flight Control as a repellent for Canada goose (Branta canadensis) control in Fort Collins, Colorado

Flight Control, containing anthraquinone, was field tested during 1997 in Colorado as a repellent to keep Canada geese (Branta canadensis) off turf. The product was sprayed at a rate of 1.9 kg per ha, using a boom sprayer towed by a golf cart. The reduction in goose numbers on the treatment plot was 95.1% ten days after application. A decline of 64.7% in the number of goose droppings on the area was recorded.

Potential bird repellents to reduce bird damage to lettuce seed and seedlings

The authors evaluated the effectiveness of ReJeX-iT® AG-145, Mesurol®, activated charcoal, lime, and fipronil to reduce homed lark damage to lettuce seeds and seedlings. In Experiment 1, homed larks consumed significantly more feed mixture (50:50 grains and lettuce seed) than untreated clay-coated lettuce seed in a three-day choice-test. In Experiment 2, where clay-coated lettuce seed was treated with ReJeX-iT® AG-145, Mesurol®, activated charcoal, or lime, there was no significant difference in consumption of untreated clay-coated lettuce seed and treated clay-coated lettuce seed. Homed larks consumed insignificant amounts of all seed treatments including untreated coated lettuce seed. In this experiment homed larks lost an average of 28% of their body weight over the three-day test period. It was concluded that the clay seed coating alone reduced damage significantly. In the aviary test, flats of sprouting lettuce seedlings were sprayed with Mesurol® (4 kg/ha), ReJeX-iT® AG-145 (64 kg/ha), lime (32 kg/ha), activated charcoal (32 kg/ha), and fipronil (4 kg/ha). Mesurol®, ReJeX-iT® AG-145, and lime significantly reduced consumption of lettuce seedlings over a four-day test period. Even though lime significantly reduced consumption, homed larks still consumed over 50% of the available lettuce seedlings. Field evaluations are warranted with Mesurol® and ReJeX-iT® AG-145.

Development of seed treatments to control blackbirds

Bird repellents to protect seeds are a potentially important aspect of integrated vertebrate pest management strategies. Yet, there currently are no repellents registered for seed treatment uses. This is due not to lack of effective candidate compounds, but to monetary and regulatory constraints that inhibit commercialization of promising compounds. Two examples of this dilemma are methiocarb and anthraquinone, each of which has considerable potential for bird repellent uses and each of which faces considerable registration hurdles as prospective seed treatment compounds. A concerted, coordinated effort among private industry, producer groups, and state and federal agencies may be the best strategy to bring potentially useful repellents to commercial reality.

Predator urines as chemical barriers to white-tailed deer

The authors assessed whether bobcat (Lynx rufus) or coyote (Canis latrans) urine could reduce white-tailed deer (Odocoileus virginianus) use of established feeding areas or trails. A four-week experiment evaluating deer use of eight feeding stations, four each with coyote or bobcat urine was conducted at a 2,200 ha fenced facility in northern Ohio with high deer densities (38/km2). At this same facility, the authors also monitored deer use of four trails where coyote urine was applied. For both experiments, urine was placed in holders positioned at ground level within 2 m of the area being protected. The number of deer entering feeding stations after two weeks exposure to predator urines was 15 to 24% less (P <0.05) than the number of deer entering feeding stations during pretreatment. Deer use of trails did not decrease in response to presence of coyote urine. It was concluded that predator urines used as a chemical barrier were of limited effectiveness in deterring high concentrations of white-tailed deer from areas with established sources of food and ineffective in deterring deer from trails.

Are wildlife-caused losses of agriculture increasing?

Both the percent of producers reporting and the value of wildlife-caused losses increased from 1989 to 1994. In 1994, 58% of respondents reported wildlife-caused losses of their agricultural commodities, an increase from the 55% of respondents who reported losses in 1989. Based on the median value of producer-estimated loss, wildlife-caused losses cost producers approximately $591 million in 1994, $130 million more than in 1989. Losses based on producer estimates have been consistent with field-measured estimates of damage. While these losses represent 1% of the value of agricultural production, losses were not evenly distributed and 23% of producers estimated losses of >$500, an amount that is psychologically significant if not also economically significant. While catfish losses to wildlife were 4% of the total sale value of catfish in 1996, the losses were equivalent to one-sixth to one-third of the average catfish producers’ profit. Producers’ ability to predict the location of their crop losses as well as consistent patterns of losses based on field assessments suggests that wildlife managers may be able to develop models of wildlife damage that would allow them to better assist producers in planning agricultural production so that wildlife-caused losses are reduced. Given the increasing populations of many wildlife species and the declining habitat base for supporting those populations, wildlife managers will need to increasingly rely on cooperative relationships with agricultural producers. Management of wildlife damage relative to agricultural needs will increasingly challenge the wildlife profession in the coming years. Wildlife managers must recognize the magnitude and distribution of wildlife-caused damage to agriculture and consider both perceptions and damage in their decisions about wildlife management.

Non-predator vertebrate pest damage in California agriculture: An assessment of economic impacts in selected crops

State-wide economic impacts of non-predator vertebrate pest damage were estimated for all pests causing damage in 19 California commodities. Average field-level damage estimates and vertebrate control costs were collected for each commodity, and across six production regions. Economic impacts were estimated by comparing simulated market outcomes in the absence of vertebrate pest damage with observed market outcomes. This analysis indicates that, for the 19 commodities considered, the economic cost of vertebrate pest damage ranged between $46.9 to $162.8 million during 1995 with a mean estimated impact of $95.9 million.

Humane Society: good guys or Gestapo?

Humane Societies and Societies for the Prevention of Cruelty to Animals perform important functions for the state, the counties, the community, and the public in protecting animal rights and enforcing state animal laws. Their staffs are hardworking and well meaning, but are not trained in police work. As the Societies have the right to conduct searches, seize property, make arrests, and use deadly force, they are required by the Constitution to perform such functions only after they have shown probable cause to a neutral party and obtained a warrant. Their failure to obtain warrants before performing such intrusive functions violates trappers’ and homeowners’ civil rights which subjects the Societies to suits for damages. To truly protect the public and to protect their budgets, the Societies should train their staff in civil rights and procedures. The Societies have the powers of the police, but resist following the laws and rules that apply to the exercise of police powers. In their zeal to protect animals, they have invaded people’s property, even their houses, confiscated traps and released animals – all without warrants or other review of their actions. These actions have led to the question of whether the Societies are "Good Guys or the Gestapo?"

Manipulating habitat quality to manage vertebrate pests

Wildlife damage management has often emphasized density reduction through lethal means. In addition to facing increasing regulatory and social restrictions, this approach also faces ecological problems; density reduction without a concomitant decrease in carrying capacity may only stimulate density-dependent responses that quickly return population densities to pre-control levels. Consequently, habitat manipulation, either to reduce pest density or to divert the pest away from the commodity, has been pursued as an alternative. Habitat manipulation has proven effective in some circumstances and appears promising in others, but the approach is limited by our ability to identify limiting resources or highly preferred foods that can be manipulated economically and with the desired effect. Further, habitat manipulation is not always a long-term solution, may have unwanted effects on non-target species, and may be ineffective if not viewed on a regional scale. Nonetheless, the approach is promising in certain situations. Further research is needed.

Wildlife damage and control research and extension programs: cost recovery strategies

This paper discusses cost recovery strategies for vertebrate pest control research and extension programs. It gives an historical background using California examples about how these programs have been supported in the past. Current situations and future trends in supporting research and extension in the vertebrate pest area are also discussed.

Are barn owls a biological control for gophers? Evaluating effectiveness in vineyards and orchards

Several rodent species cause damage in vineyards and orchards. Current efforts to reduce chemicals used to control rodents are encouraging development of alternative practices, such as biological control. For several years growers in California have been installing artificial owl nest boxes to attract barn owls with the hope of reducing rodents, especially gophers, through predation. Effectiveness of barn owls as biological control of gophers in vineyards and orchards is unknown. The purpose of the study was to use growers surveys and diet analysis to assess the effectiveness of installing barn owl nest boxes to control gophers. Surveys of growers that installed artificial nest boxes reported that 40% of boxes were occupied within six months of installation. Of those growers with occupied nest boxes, however, only 23% felt that barn owls were effective in controlling gophers on their lands. The diet results indicated that barn owls most frequently prey upon gophers and voles. Barn owls prey upon both adult and juvenile gophers, and juvenile gophers were especially vulnerable during spring and summer. The findings provide little evidence that barn owls are effective in controlling gophers. With further research the approach might prove useful, but only when used in concert with other control approaches such as trapping and rodenticides.

Rabbit calicivirus: Update on a new biological control for pest rabbits in Australia

Rabbit calicivirus disease (RCD), also known as rabbit haemorrhagic disease, is being used to control wild rabbits in Australia. Deliberate release of RCD followed extensive non-target animal and human testing and consideration of some 472 submissions. A national monitoring and surveillance program is in place to quantify the impact of RCD on rabbits, rabbit damage, predators, competitors, and ecosystems. Preliminary data suggest wide spatial variation in RCD impact, from no observable effect to >90% mortality and marked response in competitors and vegetation. This paper provides an overview of rabbit impact in Australia, details of the considerations and testing that preceded a decision to release, and results of impact studies to date.

Risk assessment for importing and keeping exotic vertebrates

Exotic animals can establish wild populations that may cause serious adverse economic and environmental impacts. In Australia, there are a number of species currently kept in captivity that would pose such threats were they to escape and establish. Paradoxically, there is a push to allow freer trade in animals between countries for recreational and commercial purposes. This paper considers approaches to assess and manage these risks, including the application of ecological theory to estimate the probability of escape, establishment, eradication, and harmful impact. Although some potential forms of impact are obvious, particularly for species that are pests in their natural or introduced range, others may be less so because species may change their behavior or ecology in new environments, and interact in unpredictable ways with resident plant and animal species. This uncertainty creates a need to leave a wide margin for error when assessing the risk of harmful impact.

Comparison of white mineral oil and corn oil to reduce hatchability in ring-billed gull eggs

Oiling eggs is a potential management method for controlling nuisance or depredating populations of ring-billed gulls, Canada geese, and other bird species. However, no registration for an oiling compound currently exists with the Environmental Protection Agency. Efficacy data were collected for white mineral oil and corn oil to reduce the hatchability of ring-billed gull eggs. Egg failure was 99% in corn oil, 96% in white mineral oil, and 35% in control eggs. Most treated eggs that hatched were treated early in the incubation period, 1 to 8 days after clutch completion. A Wildlife Service Technical Note on the use of com oil as an oiling agent is now available.

Barn owl nest boxes offer no solution to pocker gopher damage

The belief that native predators such as barn owls (Tyto alba) keep native rodents such as pocket gophers (Thomomys spp.) in check has a long history, in spite of a lack of evidence that such predators play any role in lowering pest rodent populations to the extent that their pest status is measurably influenced. Attempts to artificially increase native predators such as barn owls in the hope of increasing predation on native pest rodents is not new and has been explored many times in the past, but as yet evidence of success is absent. Since predation is a slow ongoing process, two biological principles work to nullify any negative effect on populations of rodents with high reproductive propensities. The belief that predators somehow control their prey is challenged as a biological control approach, and proven gopher management methods offered in its place.

Wildlife information sources and search methods on the internet

Vertebrate pest damage information is pulled from a variety of disciplines ranging from wildlife management to psychology. The Internet has opened the door to what seems to be an unending number of information sources. Researchers can become overwhelmed by the choices and different levels of information available. The correct use of search engines and a checklist of criteria to evaluate the quality of information obtained can help to eliminate the extraneous information and make the time spent on the Internet more productive. There are a large number of wildlife, biology, environmental, and other related sites that are especially useful to the wildlife damage management community.

Development of an Internet Center for Wildlife Damage Management

Information, materials, and services on wildlife damage management are available through educational institutions, agencies, and private industry, but access is highly variable, depending on the location and type of problem that exists. With the development of the worldwide web, electronic information on vertebrate pests has proliferated, but access by direct links or browsers has limitations. The authors have developed a website that· will serve as an Internet Center for information on wildlife damage management. It provides links to web-based publications, reference materials, list servers, agency and organization websites, home-study and certification programs, and information and service providers. The Internet Center will significantly increase public awareness and understanding of wildlife damage problems. It will facilitate distribution of information to the public and improve communication among resource providers. Ultimately, the Center will increase implementation of integrated pest management (IPM) practices that will lead to increased economic and environmental benefits.