The concept of the Vertebrate Pest Conference originated in early 1960 from discussions among representatives of the University of California; the California Dept. of Fish & Game; the California Dept. of Agriculture; the California Dept. of Public Health; and the Branch of Predator and Rodent Control, Bureau of Sport Fisheries and Wildlife, U.S. Fish & Wildlife Service. The original participants recognized that few published documents on vertebrate pest control were available, as such information was typically contained within in-house reports of the various agencies that were largely unavailable and unable to be cited. Dr. Walter E. "Howdy" Howard of UC realized that having a conference would permit a Proceedings to be published, in which this information could be made widely available.
To plan such a conference, the organizing group, chaired by Dr. Howard, became the Vertebrate Pest Control Technical Committee, which arranged and hosted the first "Vertebrate Pest Control Conference" held in Sacramento on February 6 & 7, 1962. The planning committee formally became an incorporated non-profit entity in 1975, and the Vertebrate Pest Conference is now held in late winter or early spring every two years. It is the most widely-recognized conference of its kind worldwide.
Detailed histories of the development of this Conference are found in these publications:
Volume 15, 1992
In this Keynote Address, the author draws a distinction between conservationists and “environmentalist activists” (also termed “preservationists”). In the latter group, he includes “deep ecologists” and “greens.” He postulates that “deep ecologists” either ‘drop out’ of society or join radical environmental or animal rights groups that reject technology and a utilitarian perspective toward nature; such groups include Greenpeace, PETA, the Animal Liberation Front, and Earth First!. By contrast, “greens” are more pragmatic and willing to compromise, while seeking to achieve a socialist, redistributionist society, centrally controlled and planned by ‘environmental experts’ such as themselves. Both groups of environmentalists descend from the philosophies of Lynn White, Jr. and Arne Naess, and the animal rights proponents are guided by writings of Peter Singer, Tom Regan, and Roderick Frazier Nash. The author discusses the concept of “intrinsic value” of all species, noting that those who decry human “exploitation of nature” are the first to deny that humans are part of nature. The author provides examples of how activists’ organizations have manipulated scientific data and used publicity to argue against killing of animals for any reason (e.g., opposing predator control to protect livestock, and rodent control to protect agriculture and public health), and use of all pesticides (e.g., claims that Alar, a plant growth regulator used on apples, causes cancer). He notes, "Nowhere have I found the corruption of science more acute than in the EPA." He concludes by suggesting ways that those involved in vertebrate pest control can more effectively communicate with the public about the need for science-based, wise management of natural resources.
Changes in the Animal Damage Control (ADC) program are reviewed relative to changes in American societal background and attitudes. Many of the program changes that occurred in the past were imposed on ADC in response to external factors, while more recent program changes have been and will continue to be more self-directed. Examples of ADC's proactive approach to dealing with critical issues are provided.
A national survey of Animal Damage Control (ADC) method research needs was conducted in 1990. ADC program State Directors provided responses for each state. Individual state data was aggregated into a national ranking list of ADC program priorities for directing future wildlife damage control methods research. Species groups ranking highest, nationally, included: blackbird/starling, waterfowl, coyote/fox/dog, wading bird/cormorant and ungulate groups. Species groups ranking lowest, nationally, included: swallow, crane, rabbit, porcupine and hog groups.
Many vertebrate pesticides used by the Bureau of Biological Survey at the turn of the century were registered by the U.S. Fish and Wildlife Service (USFWS) beginning in 1960 with the U.S. Department of Agriculture (USDA). A review of archives and other documents at the Denver Wildlife Research Center (DWRC) has shown that a total of 72 federal registrations were established by the USFWS between 1960 and 1985. Because of increased regulation by the U.S. Environmental Protection Agency (EPA), selective transfers from USFWS to USDA, voluntary cancellations, conversions to state local need registrations, and a reduced development pace, there are now only 21 federal vertebrate pesticide registrations. They are maintained by the Animal and Plant Health Inspection Service (APHIS) for the Animal Damage Control (ADC) program. As a result of a 1988 Amendment to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA 88), DWRC initiated in 1989 an extensive reregistration program for ADC's vertebrate pesticides. In the past three years, DWRC and its cooperators have submitted 188 studies in support of the reregistration of products containing strychnine, sodium cyanide, zinc phosphide, compound 1080, sodium nitrate, carbon, DRC-1339, and PA-14. Since 1989, the reregistration of these 8 active ingredients has taken priority over the development of new vertebrate pesticides at DWRC in order to concentrate on gathering data for these chemicals of the past. New tools to mitigate human and wildlife conflicts must continue to be the goal of present and future federal research.
The Pocatello Supply Depot (Depot or PSD), established in 1933, descended from the U.S. Biological Survey Bait (USBS) Mixing Station which originated in 1930 in McCammon, Idaho. The Depot was approved by a Congressional Resolution signed by the President in 1936. The Depot has functioned since 1937 under a Cooperative Service Agreement with the Greater Pocatello Chamber of Commerce who serves as trustee to the "Depot Revolving Fund." The mission of the PSD is to provide specialized products and services for the Animal Damage Control (ADC) program and others engaged in wildlife damage management programs. The PSD fills a very special niche in providing a stable source for ADC tools that are often not readily or consistently available from private industry. The major products of the Depot include Gas Cartridges for Rodents, M-44 devices and capsules, and strychnine and zinc phosphide grain baits. Minor products include Starlicide Technical, Gas Cartridges for Coyotes, zinc phosphide technical rodenticides, Fatty Acid and Monkey Pheromone scents and scent tabs, ADC signs, Neutroleum Alpha deodorizer, Electronic Guards, trap pan tension devices, and grain bags, dippers and probes for pocket gopher control.
The terms "good" and ''bad" are completely subjective, yet the public has expectations that wildlife damage management professionals "do bad things to good animals." It is argued that wildlife damage management decisions are made in a value-laden context, with science in a supportive role. The principle of collective human values is the driving force of society's concerns, and collective values are currently highlighting animal welfare and other environmental concerns. Wildlife damage management professionals could modify their operational paradigm from a focus on populations of animals to a focus on aggregations of individual animals in order to respond proactively to both emerging and recognized social values.
Developing a strategy of predator control for the protection of the California least tern: A case study
In recent years, predation has been determined to be a seriously limiting factor in the reproduction of the endangered California least tern (Sterna antillarum browni) at many of its nesting colonies. Among them is a major colony at Camp Pendleton Marine Corps Base near Oceanside, CA. Early efforts to control predation were limited in effectiveness. In 1988, the U.S. Department of Agriculture, Animal Damage Control Program was contracted to provide control of mammalian and avian predators. The development of the successful strategy that has evolved over four years is discussed, with emphasis on the development and application of techniques, and the timing and areas of control.
With the establishment of the U.S. Department of Agriculture's Animal Damage Control operational program in Hawaii, the agency has expanded its activities to include protecting endangered species in Hawaii, American Samoa, and may soon be operating in Guam and the Commonwealth of the Northern Marianas. Endangered species recovery plans and technical reports of species in the Pacific Islands outline a role for the Animal Damage Control program in recovery efforts.
The commensal rodent pest species have spread from their ancestral homes in Asia to inhabit many natural ecosystems worldwide. The introduction of these exotics has often had a significant effect on endemic plant and animal species but their impact has, perhaps, been most severe on off-shore and oceanic islands where nesting birds, insects, terrestrial molluscs, reptiles and amphibians are all vulnerable. Conservationists have used a variety of control approaches either to reduce or eliminate the pressure of competition and predation exerted by introduced rodents on island populations of endangered species. Successful projects have involved a sequence of carefully-planned operations. Firstly, an assessment of the nature and scope of the rodent threat is undertaken to permit the development of a control programme with the maximum chance of success. A second element is the estimation of the likely impact of intended control operations on non-targets in these highly sensitive environments. A pilot study may be required prior to the third and final stage, that of implementation and then monitoring the effect of the programme on target pests, sympatric non-targets and the species that are the object of the conservation effort. The anticoagulant rodenticide brodifacoum (trade names 'Klerat' and 'Talon') is used in conservation projects worldwide. This paper puts forward general principles for adoption when employing this compound for conservation and exemplifies the approach advocated with descriptions of a number of projects undertaken for the benefit of a variety of endangered species.
Coyote control to protect endangered San Joaquin kit foxes at the Naval Petroleum Reserves, California
We investigated the effectiveness of a coyote (Canis latrans) control program implemented to increase numbers of endangered San Joaquin kit foxes (Vulpes macrotis mutica) at the Naval Petroleum Reserves in California (NPRC). Between 1980 and 1985, the kit fox population on NPRC declined approximately 66% while coyote abundance apparently increased. Coyote predation was identified as the primary cause of mortality for kit foxes. From 1985 to 1990, the U. S. Department of Energy (DOE) sponsored a program to kill coyotes with the objective being to reduce predation on kit foxes and increase fox numbers. Control methods during the first 4 years were limited to trapping, shooting, and denning. In the last 12 months of the program, aerial gunning was implemented and significantly increased control intensity. This more intensive strategy was not conducted for a sufficient length of time to evaluate its effectiveness. Thus, conclusions regarding coyote control at NPRC are based primarily on the first 4 years of the program. During the 5-year effort, 591 coyotes were killed. Although coyote scent-station indices declined during the period of control, the contribution of the control effort to this decline is unclear. Reproductive rates of female coyotes did not exhibit a compensatory increase as is commonly observed when coyote populations are artificially depressed. After control was initiated, kit fox capture indices and survival rates did not increase, and the proportion of fox deaths due to coyotes did not decrease. The number of coyotes removed annually may not have been sufficient to effectively reduce coyote abundance. Kit fox and coyote population trends both were significantly correlated to lagomorph abundance. Thus, food availability probably was the primary factor influencing the population dynamics of both predators. Control efforts were discontinued pending further consideration of the merits of control and its potential efficacy at NPRC.
Problems with management of a native predator on a threatened species: Raven predation oesert tortoises
Common ravens (Corvus corax) are a major predator on the threatened desert tortoise (Gopherus [= Xerobates] agassizii). Large numbers of juvenile tortoise shells have been found beneath known raven nests and perches; many shells that show evidence consistent with raven predation have been found sporadically throughout the range of the tortoise; significant proportional decreases in juvenile size/age class distributions have been identified; and people have observed ravens killing, carrying, and consuming juveniles. In 1988 the U. S. Bureau of Land Management initiated a process to evaluate, design, and implement a program to reduce raven predation on desert tortoises. A pilot program was temporarily halted by a lawsuit filed by the Humane Society of the United States, and a draft long-term plan and Draft Environmental Impact Statement were subsequently issued and are now being modified. Several complex issues have arisen in attempting to design and implement control of ravens including: pitting one native species against another, making management decisions in light of data of varying scientific validity and depth, targeting individuals versus populations, and managing a predation problem over a broad geographic range. Addressing each of the concerns is highly problematic and the solutions are not always satisfying.
Nontarget hazards associated with egg baits used to control corvid depredations on endangered California least tern eggs at Camp Pendleton, California–1990 (Abstract)
Several small nesting colonies of the endangered California least tern (Sterna antillarum browni) remain along the California coast. The largest of these is located on Camp Pendleton Marine Base in southern California. Many forms of disturbance have apparently contributed to the decline of this tern species, including corvid, primarily raven (Corvus corax) predation on the eggs. Efforts to eliminate corvid predation have primarily focused on shooting offending birds; this method is selective, but it has inherent public safety problems. In 1988, biologists from the Denver Wildlife Research Center (DWRC) and the U.S. Navy, in cooperation with USDA Animal Damage Control personnel, conducted a pilot study at Camp Pendleton to determine if corvids could be selectively removed by consuming hard-boiled chicken eggs treated with the avicide DRC-1339. Thirty-six treated eggs, 6 per clutch, were exposed in dummy ground nests in raven nesting territories in the vicinity of one of the tern colonies. Egg baits were readily consumed by ravens, but several others were cached. After selectively removing only three to four ravens with this method, the least tern fledging rate for 1988 at Camp Pendleton was the highest in recent years. The success of this pilot study led to a series of Navy-funded studies conducted by DWRC biologists from 1989 through 1992, including investigations of the activities of ravens in the vicinity of tern colonies and the development/evaluation of potential methods to reduce corvid predation on least tern eggs. This abstract describes research conducted at Camp Pendleton in 1990 to identify species of nontarget animals that might consume (1) egg baits that could be used to deliver a toxicant and (2) the carcasses of corvids that might be killed by consuming toxicant-treated eggs. Eighty-seven untreated eggs and 13 untreated corvid carcasses were placed in various habitats and locations within 4 to 5 km of tern colonies during the tern breeding season. Some were placed in known raven nesting territories. One to two eggs were secured to each of 15 4-ft-high bait platforms and placed on the ground at 7 locations. Eggs were replenished as necessary during an observation period. A fresh carcass was secured to the ground at each of 13 locations. Each site was observed continuously for approximately 72 to 96 hours by infra-red, motion-sensing cameras to determine nontarget activity. No nontarget animals consumed eggs from platforms during 1,112 hours of observations. During 433 hours of observations of eggs on the ground, only one species of nontarget animal, the striped skunk (Mephitis mephitis), was recorded feeding on eggs at one station during the night. Gulls (Larus sp.) were continually present in large numbers in the vicinity of exposed eggs, but did not feed on them. Observations of untreated corvid carcasses, monitored for 1,030 hours, revealed only occasional scavenging by skunk, opossum (Didelphis marsupialis), turkey vulture (Cathartes aura), and raven. The data suggest that eggs used in a toxicant baiting operation (e.g., DRC-1339) to control corvids, or carcasses of corvids dying as a result of such a baiting operation, pose minimal nontarget hazards. Although there are no data available on the primary and secondary toxicity of DRC-1339 to the nontarget species observed in this study, data from other species tested with this compound suggest none is likely to be killed by ingesting DRC-1339-treated eggs, nor by scavenging corvid carcasses. Of the 87 eggs used in this study, ravens and crows, the target species consumed 22 (46%) of the 48 eggs placed on platforms. Thirty-three of the 39 eggs placed on the ground were consumed− 7 (21%) by skunk(s) at one station at night and 26 (79%) by ravens, exclusively within nesting territories. It appears that ground baiting during daylight hours is the most effective method of exposing treated eggs to target corvids, while minimizing nontarget consumption of eggs.
Male red-winged blackbirds (Agelaius phoeniceus) being gregarious, and causing heavy damage to corn crops in the northeast, including southern Quebec and Ontario, sterilization has been studied as a means to manage their populations. With chemosterilants (thiotepa and Ornitrol®) tested, year to year variations in reproductive success occurs. The spermatogenesis is disrupted, but the overall effect is not specific. Biosterilisation with 10.0 µg doses of GnRH-analogue hormones is more specific, and the spermatogenesis is disrupted for at least a month, but several spaced injections were required. No field trials have been done yet.
In August and September 1989 and 1990, we aerially sprayed 8 cattail (Typha spp.) marshes with Rodeo® herbicide to begin evaluating its use for fragmenting dense cattail stands used by roosting blackbirds (lcterinae). Treated marshes were effectively eliminated as roost sites for blackbirds. After 2 years, cattail densities in 4 marshes treated with Rodeo® at 5.8 - 7.0 L/ha were 87 % lower than pretreatment densities (P = 0.0001 ). In 1990, we treated 4 marshes with Rodeo® at 4.7 L/ha. One year later, 6% of the cattails survived in the sprayed areas. Of 7 groups of "indicator birds," only marsh wren (Cistothorus palustris) and rail (sora, Porzana carolina; and Virginia rail, Rallus limicola) populations were adversely affected by cattail fragmentation. These preliminary results led to an increased research effort to develop marsh management techniques aimed at eliminating blackbird roosts.
The pesticide reregistration process: Collections of human health hazards data for 3-chloro-p-toluidine hydrochloride (DRC-1339)
The 1988 Amendments to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) accelerated the reregistration schedule for pesticide products registered with the Environmental Protection Agency (EPA) prior to 1984. The compound 3-chloro-p-toluidine hydrochloride (DRC-1339), an avicide registered to control 14 pest bird species, was included on Pesticide List B published by EPA. For the reregistration of DRC-1339, 44 studies were required− 22 product chemistry, 7 wildlife/aquatic hazards, 8 human/domestic animal hazards, 5 environmental fate, and 2 residue chemistry studies. In 5 acute human-health-hazards studies, DRC-1339 was found to: (1) have an oral LD50 of 330 (272-401) mg/kg in rats, (2) have a dermal LD50 of >2.0 g/kg in rabbits, (3) cause corrosive effects to the eyes of rabbits, (4) cause corrosive effects to the skin of rabbits, and (5) induce dermal sensitization in guinea pigs. Results support the current precautionary statements on the "use labels" warning of harmful ingestion, inhalation, dermal absorption and eye irritation effects to users of the active ingredient.
Colony roosting species of blackbirds (Icterinae), including European starlings (Sturnus vulgaris), can be significant pests. The chemical avicide CPT has been applied experimentally in the U.S. and France to roosting blackbirds. However, apparent effective aerial application rates are high, 44-101 kg/ha (40-90 lbs/a), and the actual efficacy, expressed as percent mortality, is difficult to determine. We assessed CPT as a respirable aerosol for potential use as a roost avicide. Starlings exposed to 17 ppm CPT for 5.5 min received lethal doses. The birds appear very sensitive to CPT administered in this manner. The methods of CPT entry into the birds include respiratory, ocular and dermal. It is proposed that a field application rate of 3.4-5.6 kg of CPT per hectare (3-5 lbs/a) would be effective.
In cold weather and early mornings, birds feeding on Avitrol® baits treated with 0.5, 1.0 and 3.0% 4-aminopyridine have shown reaction times as short as four minutes (reaction times of seven to ten minutes are common). Relatively fast reaction times, staggered arrival times of a flock at feeding sites, and delayed feeding by some members of a flock continue to result in premature reactions which frighten birds from the treated bait resulting in insufficient numbers reacting to give the desired repellency. This paper reports preliminary results of an effort to slow chemical absorption in an attempt to minimize this problem.
Alpha-chloralose efficacy in capturing nuisance waterfowl and pigeons and current status of FDA registration
During 1990 and 1991 we conducted safety, efficacy and clinical trials required to register alpha-chloralose (A-C) for capturing nuisance waterfowl and pigeons with the U.S. Food and Drug Administration (FDA). We determined the Most Effective Dose (MED) to be 30 and 60 mg of A-C/kg of body weight for capturing waterfowl and pigeons, respectively. We conducted 11 field trials in 4 states, capturing 587 waterfowl and 1,370 pigeons with 8% mortality for ducks, 0% for geese, and 6% for pigeons. We submitted a New Animal Drug Application to FDA in October 1991 and anticipate registration in 1992.
Information concerning fifteen species of birds associated with twenty-five buildings on the University of California at Berkeley has been collected for nineteen years. Fourteen species are included under three minor associations (temporary roosters, building invaders, and species that nest on, or in buildings in small numbers). Two species (cliff swallows, and feral pigeons) have caused major problems. Feral pigeon problems have been the most difficult and complex to resolve. Case histories are used to describe problems associated with these birds (ectoparasites, building defacement and messiness, slipping hazards and noise), and human contributions to the problems (feeding, trap vandalism, and legal and political constraints, and ecological and architectural design factors). Site specific solutions are emphasized, and future concerns and goals are discussed.
In Europe, starlings are widely distributed and comprise both resident and migrant populations. These cause various kinds of damage which varies with the crops grown in different European Economic Community (EEC) countries. Although EEC member states are governed by the same legislation on bird protection, each state interprets the Community legislation in its own national legislation. This leads to different national approaches to the prevention of starling damage, with little information exchange between member states. The establishment of an EEC (or wider) working group on bird pests is recommended to coordinate research and development.
Two field trials were conducted to determine the effectiveness of Avitrol® (4-aminopyridine) mixed grains 0.50% in the repelling of house finches (Carpodacus mexicana) from two vineyards in Sonoma County. In the first trial, two properties were prebaited for twelve and fourteen days respectively. After the removal of the prebait, Avitrol treated grain mixture was then placed in the bait troughs for a period of from two to four days. A count of the house finch (linnets) number visiting the troughs during the prebaiting and treatment phases of the trial was recorded. Subsequent linnet counts were made to determine the days of protection which were achieved from the treatment. In the second trial the methods were similar, however, only one of the two selected properties was treated. In both trials, trapping with a modified Australian crow trap was done when necessary to census existing house finch populations and to mitigate further crop damage. The trials indicate that Avitrol mixed grain baits can provide good long term protection to smaller vineyards with low to moderate linnet populations. In the larger vineyards with approximately 1,000 linnets, only short term control was achieved.
The most significant damage inflicted by birds in Australia is to germinating cereal and to ripening sunflower and fruit crops. The main pests are several native psittacine and corvid species, silvereyes (Zosterops lateralis) and European starlings (Sturnus vulgaris). The economic cost of damage is largely unquantified. While losses to industries as a whole are often low, losses to individual growers may be severe, and losses are distributed patchily in space and time. Shooting is the most widely practiced and most ineffective bird control technique used in Australia. Despite the high numbers of birds killed, damage persists, and disturbance caused by shooting and scare devices may actually increase damage. Trapping and export of native birds is frequently suggested as a solution but would be ineffective for damage control. Illegal poisoning is thought to have caused significant reductions in some parrot populations, but has not prevented crop damage. Decoy feeding shows promise for damage control in winter cereals. One site attracted 4,000 cockatoos for most of the seeding and germination phase. For sunflower, the main problem is rendering the main crop less attractive than the decoy. Netting is cost-effective even at moderate to low levels of bird damage for intensive growing systems with new varieties of high-yielding stonefruit. Research is needed on techniques to assess the cost of damage. The cost-effectiveness of damage control techniques can then be assessed. There is also a need for more studies on the biology of pest birds, in relation to the potential mitigation of crop damage by habitat modification or changes in crop growing practices.
We reviewed the historical and current status of the American crow (Corvus brachyrhynchos), urban crow roosts and control efforts in California. Crows aggregate in traditional winter roosting areas. In the late 1930s most crows in California roosted in the Sacramento Valley in rural locations. Crow roosts were not a concern except for potential damage to adjacent farmlands. From the 1960s through 1980s crows colonized urban areas for nesting and winter roosting. A phone survey of vertebrate pest management officials indicated all known roosts were in urban areas, with most occurring in the Sacramento Valley. From 1970 to 1989 the winter crow population in the Central Valley of California doubled, with more crows found in the Sacramento Valley than the San Joaquin Valley. In the late 1980s crows in a traditional roost area in Yuba City, Sutter County, increased to 1 million birds. Political pressure prevented attempts at population reduction in 1991 and 1992 and led to examination of non-lethal techniques to disperse crows from urban roosts. Methods and materials tested included mylar tape, strobe lights, netting, monofilament lines, eyespot balloons, pyrotechnic devices, water-misters, sticky repellents, and taped crow and owl vocalizations. Qualitative evaluations by residents and local officials indicated strips of mylar tape tied on branch tips and pyrotechnic devices were relatively effective in dispersing crows.
Ultrasonic or high-frequency sound-producing devices are marketed as a scaring or frightening method for bird control. Although inaudible to humans, most birds also do not hear in the ultrasonic frequency ranges of above 20,000 Hz, thus the credibility of advertised claims raises questions. A review of efficacy studies conducted and published by a number of researchers fails to demonstrate the usefulness of such bird control devices.
Canada geese (Branta canadensis) in the Reno-Sparks, Nevada urban area have become a problem of increasing significance. Nuisance complaints from city parks, golf courses, and housing developments augment the bird hazard to aircraft operations at the local airport. Eleven goose collisions with commercial aircraft, between January 1986 and April 1989, caused $250,000 in structural damages but no injuries or loss of human life, The Federal Aviation Administration required action be taken to reduce the hazard if airport certification was to continue. A multi-agency task force was formed to develop and implement an integrated pest management plan. Population surveys and daily observations were conducted to quantify the problem and evaluate results of control methods. Short term controls included disruption of roosting and feeding sites adjacent to the airport, hazing, public education, and gosling relocation. Development of a suburban goose refuge was proposed as a long term control. Long term management ramifications of this integrated approach were improved agency services to constituents, vigor of the local goose population, and quality of life for people through mutual coexistence with the birds.
Urban-suburban Canada geese (Branta canadensis) create nuisance problems at their foraging sites by littering them with feces. An ecological approach to the problem involves inducing the geese to use alternate foraging sites by reducing the attractiveness of problem sites. This can be accomplished by reducing the forage quality at the nuisance site by not fertilizing and infrequently mowing the lawn or by replacing the lawn with a less palatable grass species or other ground cover. Further, sites can be made less attractive to geese if they are surrounded by tall trees which make it harder for geese to land or take off, and planting bushes and hedges to reduce a goose's ability to watch for approaching predators. Another approach involves relocating roosting areas to more remote sites so that geese have to expend greater time and energy to reach the problem site.
Scarecrows and raptor models are fairly common traditional methods of attempting to frighten unwanted birds. Their effectiveness depends on the conditions under which they are used and the unwanted bird species involved. Best results are obtained from those that are most lifelike and have motion. When coupled with loud startling sounds or recorded distress calls their effectiveness is generally enhanced. Habituation by at least some birds is inevitable so the duration of effectiveness diminishes with time. It is essential to know what works best in a given situation so those methods can be employed to achieve maximum efficiency. An understanding of the limitations of these devices will temper expectations to a realistic level.
Nonlethal repellents: The development of cost-effective, practical solutions to agricultural and industrial problems
Repellents substances and devices cause pest species to avoid otherwise attractive or palatable materials. For birds, repellents can be visual, auditory, pyrotechnic, tactile, chemosensory, physiologic, or physical. Here, we consider chemical agents only. Few substances are registered with the U.S. Environmental Protection Agency (EPA), and thus legally available for use. This lack of available bird repellent technology reflects the small demonstrable economic impact of many agricultural bird damage problems. Accurate information about damage and market size is virtually nonexistent, and private companies are reluctant to invest resources in the unknown. To successfully commercialize new repellents, clearly lucrative markets must be identified. Efforts must be made to empirically quantify damage and to estimate whether control methods are economical relative to the protection that they confer. We intend the present manuscript as a first step in these directions.
Methyl anthranilate (MA) is a grape-flavored food additive that is aversive to birds. Previous studies had indicated that anthranilates can deter frugivorous birds but that anthranilates are phytotoxic. In this study, I tested the bird repellency to 2 MA formulations on blueberry plants in a large flight pen. Neither MA formulation protected the blueberries from damage by cedar waxwings (Bombycilla cedrorum) or European starlings (Sturnus vulgaris). The encapsulated formulation, however, was nonphytotoxic. Due to the on-going need for safe bird deterrent compounds, further development and testing of MA as a bird repellent on fruit is warranted. The most fruitful and cost-effective approach, however, might be to integrate MA use with other bird deterrent methods to lower the attractiveness of the cultivated fruit relative to available alternate foods.
ReJeX-iT™ brand bird aversion agents have been formulated from non-toxic, food-grade ingredients that meet or exceed US Food Chemical Codex (FCC) and US Pharmacopeia (USP) specifications. The products, based on methyl anthranilate (MA) as the active ingredient have been developed in liquid and powder form to cover the widest possible range of applications. EPA/FIFRA registration is being actively pursued for all products.
Anthranilitic acid derivatives, used as common food additives, have been explored as bird repellent agents for a number of years. Research in this study show that methyl anthranilate, when exposed to the UV spectrum of sunlight, readily dissipates within 64 hours. The addition of surfactants and extenders did not appreciably alter the degradation curve, nor did they lessen the phytotoxic properties of the chemical. Field trials under IR-4 guidance and support indicate that methyl anthranilate (MA) is an effective, biodegradable, nontoxic bird repellent. In formulation with a lipid molecular binding compound, degradation of methyl anthranilate was extended from four to ten days. Phytotoxicity, at effective application rates, was eliminated. Damage to cherries was reduced 43% to 98% depending on cultivar, number of birds present, and crop loads when the treated crops were compared with untreated crops. Depredation of blueberries was reduced 65% and 99% for two varieties. Feeding on wine grapes was diminished 58% to 88%, depending on the affected vinifera. Tasters could not distinguish between treated and untreated fruit nor could certified graders find any reduction in fruit quality.
Many pesticide chemicals once used to control vertebrate pests are no longer registered in the U.S. Changes in pesticide laws and regulations have played a major role in the loss of vertebrate pesticides, but relatively few products, uses, or compounds have been lost because the U.S. Environmental Protection Agency (EPA) determined that they were too hazardous to be registered. Most canceled products, use patterns, and chemicals have been lost because their registrants abandoned them, choosing not to pay the fees or data development costs necessary to maintain registrations. Pesticide users or other interested parties may be able to "save" a threatened use of a pesticide by generating the data needed to assess the claim. Federal law now requires EPA to publish lists of pesticide chemicals that are in danger of being lost because of nonsupport by their basic registrants.
The anticoagulant rodenticides were discovered in the 1940s and their advantages of efficacy and safety quickly resulted in their use dominating the practice of rodent control in temperate countries. However, the development of resistance to the early compounds within a decade stimulated research culminating in the invention of a new class of anticoagulant, the second generation compounds, active against resistant strains but also overall far more potent than those previously available. A novel baiting strategy, pulsed baiting, was developed to make full use of this valuable characteristic. Pulsed baiting has enabled the use of second generation anticoagulants in situations where early products were of limited value, particularly in tropical agriculture. The future of this highly-successful group of compounds is reviewed in relation to resistance and the difficulty and cost of developing further rodenticides.
Nearly half a century ago anticoagulant rodenticides changed the nature of rodent control. Warfarin, and succeeding first-generation compounds, provided effective and increasingly safe baits for reducing commensal rodent populations. Environmental deficiencies were overridden by these "miracle" chemicals, but excessive and irresponsible use selected for resistant populations. Second-generation compounds with a single-feeding characteristic have controlled such resistant populations, at least initially. But use extensions to crop and field areas have been held back by registration requirements, costs, and concerns over local effects on predators. New compounds, formulations, and applications in the near future are likely to be quite limited.
The characteristics and history of behavioural resistance in inner-city house mice (Mus domesticus) in the U. K.
Since 1984 pest control operatives in some inner-city areas in the U.K. have found that house mice have become increasingly difficult to control. Mice in these very localised areas have stopped taking rodenticide bait from bait containers, a phenomenon referred to here as behavioural resistance. We report here preliminary experiments designed to characterise the phenomenon more precisely by comparing West Midlands behaviourally resistant (WMBR) populations with non-resistant (BC) populations in Berkshire. We investigated three hypotheses, that compared with non-resistant populations, resistant mice 1) are less likely to enter conventional live-capture traps; 2) have unusual food preferences; and 3) avoid bait boxes. Longworth, Sherman and 'Tichy' traps were all less successful at resistant sites, the Longworth being ineffective and the Sherman almost so. WMBR mice also avoided Longworth traps more than BC mice in small-scale laboratory experiments designed to exclude environmental differences. A field trial showed that resistant mice much prefer peanut butter and Test Food 3 (which cannot be named for commercial confidentiality) to canary seed and Betalard (a proprietary rodenticide), but in this trial bait boxes were not avoided more than bait trays.
Anticoagulant rodenticides may pose a secondary poisoning hazard to non-target predators and scavengers because of the time-delay between ingestion of a lethal dose and death of a target rodent. We investigated some pre-lethal effects of an anticoagulant rodenticide on the behaviour of wild rats in cages and in enclosures. We found that social interactions shortened time to death, that most rats died away from cover and that thigmotactic behaviour was reduced in the enclosures. The normal light-dark rhythm was upset in intoxicated rats in both cages and enclosures. Thus pre-lethal effects are likely to alter the exposure of predators and scavengers to intoxicated rats, and diurnal predators may be exposed more than nocturnal predators as a consequence. We stress the need to extend these behaviour studies to the field.
The effectiveness of difethialone (LM 2219) for controlling Norway rats and house mice under field conditions
Under an Environmental Protection Agency Experimental Use Permit, a pelleted bait containing 0.0025% (25 ppm) of the new anticoagulant difethialone was tested to determine the effectiveness in controlling Norway rats (Rattus norvegicus) and house mice (Mus musculus). Sixteen (16) individual field studies were conducted in five (5) geographical locations of the United States. The results were conclusive in showing that difethialone bait formulated at 25 ppm was both palatable and efficacious in controlling both Norway rats and house mice under actual field conditions.
The efficacy of the newly developed anticoagulant rodenticide, difethialone, was evaluated against various rodent species in laboratory and fields. Difethialone at 0.025% concentration in the form of loose bait (broken wheat and rice + veg. oil + garlic powder) gave absolute mortality in Rattus rattus, Mus musculus, Funambulus pennanti, and Meriones hurrianae during 'no-choice' tests in one day feeding. No significant difference was noted in poison bait intake and mean days to death between two and three days poison feeding. Mean days to death were ranged between 2.9 to 5.70 in all the species tested. In fields, baiting with the same loose bait (0.025%) was performed in the live burrows and 88.89% control recorded on the 4th day after treatment. In another trial, three large hay stacks situated near wheat, barley and mustard crops were also treated with difethialone (0.025%) and 90.47, 94.44 and 80.00% kills were recorded respectively. The results of the present investigation prove high potency and acceptability of difethialone against both domestic as well as field rodents.
Studies on bait preference and acceptance of flocoumafen in Rattus rattus infesting poultry farms and godowns
In India, the most common commensal rodent, Rattus rattus rufescens, is often difficult to control using rodenticide baits. On poultry farms, it is commonly recommended that rodenticides be formulated using poultry feed as the main ingredient, but control is often ineffective. In laboratory studies, we evaluated bait acceptance using rats collected from poultry farms and from food grain godowns (local grain storage structures). Rats from poultry farms preferred formulations of millet + 2% arachis oil + 1% sugar to poultry feed, while rats from godowns preferred sorghum + 2% sesame oil + 1% sugar. We discuss the significance of observed diversity in bait preference. Flocoumafen at 0.005% was mixed with the two most preferred bait formulations and was provided to rats from both locations in a 2-choice test; mortality after a 1-day exposure was 50% and 62% in rats collected from poultry facilities and godowns, respectively. In both cases, rats consumed more flocoumafen bait than nontoxic poultry feed. This indicates that poison baiting in poultry farms should be carried out using the most preferred feeds rather than using poultry feed.
The susceptibility of eight rodent species to a range of widely used and candidate rodenticides was determined in laboratory feeding tests. No choice and choice tests were used to assess toxicity and effect on palatability of the rodenticides to Meriones shawi (Shaw's gerbil), Arvicanthis niloticus (Nile rat), Acomys cahirinus (Egyptian Spiny mouse), Mastomys natalesis (Multumammate rat), Sigmodon hispidus (Cotton rat), Rattus exulans (Polynesian rat), and R. rattus (Ship rat) which responded differently to each chemical. The results of these tests suggest possible rodenticides suitable for control of each species. Field trials are now needed to assess the effectiveness of these compounds under practical conditions.
Evaluation of aversive agents to increase the selectivity of rodenticides with emphasis on denatonium benzoate (Bitrex) bittering agent
Aversive agents are proposed as potential additives to rodenticides to increase selectivity to the target species. Examples of various aversive agent categories are given, including odorants, tastants, and emetics, with examples of evaluations. Tastant additives have been found that do not interfere with rodenticidal efficacy. Denatonium benzoate (commercially available as Bitrex®) is an intensely bitter but non-toxic substance, being increasingly used to adulterate common household materials to reduce the potential risks involved with accidental exposures. No known prior research results have been published concerning the incorporation of Bitrex in rodenticides. Rate determination studies utilizing different rodenticidal formulations were conducted. A Bitrex level of 10 ppm was well accepted by wild commensal rats and mice in laboratory tests of brodifacoum pellet and wax block formulations (TALON®, KLERA T® rodenticides). Bait samples with this level of Bitrex (without anticoagulant) were evaluated in a human taste panel study. Samples with Bitrex were found to show significantly greater average rejection by the panel than similar samples without Bitrex. Field trial results are reviewed, which verified the efficacy of Bitrex-containing commensal rodenticides. The potential role of Bitrex or similar taste deterrents as rodenticide additives is considered opposite accidental toxicant exposure statistics, and perceptions relating to rodenticides and other pesticides.
Clinical approaches to the diagnosis of diseases and disorders in pets and domestic animals sometimes mistaken for anticoagulant toxicosis
To differentiate the causes of bleeding disorders requires a basic understanding of the hemostatic process and the proper interpretation of history, physical examination, and laboratory tests. A brief overview of the hemostatic process is presented. Tables and flow charts are provided to assist in developing a sound clinical approach to the bleeding patient through the proper assessment of history, physical examination findings, and laboratory tests. Categories of inherited and acquired bleeding disorders are briefly presented.
Which useful toxicological information can be drawn from studies on the hepatic fixation of anticoagulant rodenticides
Anticoagulant rodenticides act at the hepatic level where they are more or less fixed according to their lipophilic nature. The studies on kinetics and metabolism carried out with no toxic doses are useful to know how products act but do not allow to anticipate the toxicity risks for nontarget species, because of low residual contents. These risks can only be assessed after the administration of toxic doses taking into account the residue levels. The use of half-life to express the results is not sufficiently accurate and may lead to wrong conclusions. The studies involving the residue and secondary toxicity levels are more accurate for assessing the risks. Some examples are given in particular for bromadiolone.
Field evaluation of three anticoagulant rodenticides against Mus musculus populations in apartmental buildings in New York City
Field efficacy studies using three anticoagulant rodenticides were conducted on House mice, Mus musculus under a variety of conditions in 35 apartment buildings scattered over four boroughs of New York metropolitan area. Percent control successes and relative efficacies of various rodenticides and their formulations were determined by recording pre and post control census for about four years. After four monthly treatments, the control success rate of bromadialone (0.005%, meal form) was highest (94.5%) followed by brodifacoum (0.005%, pellet form, 91.23%) and diphacinone (77.72%) in the wax cake formulation. However, build-up of the residual mice population was faster in the case of bromadialone treatment when compared to brodifacoum (P < .01). Results of intermittent control operation, bi-monthly and biweekly, are compared and discussed with respect to mice population dynamics and properties of the rodenticides.
In view of resistance reported to have developed towards second generation anticoagulants and the problem of bait shyness and neophobia when acute rodenticides are used, it becomes imperative that methods be evolved to overcome these problems. Attempts to potentiate anticoagulants for effective rodent control is a new concept with very few studies. Experiments using two non-steroid ant-inflammatory drugs, namely ibuprofen and phenylbutazone at 80 mg/kg and 50 mg/kg body weight respectively to potentiate the action of two second generation anticoagulants, brodifacoum and bromadiolone, yielded positive results for Rattus rattus. The drugs reduced the lethal dose required for 100% mortality as well as days to death. Field trials confirmed laboratory findings.
Rodenticides with delayed action are generally more effective than fast-acting compounds because of the phenomenon of bait shyness. Calciferols have a stop-feed effect quite soon after dosing, and physiological effects are measurable within one day of dosing. We investigated whether bait shyness might result from these fairly rapid effects in the laboratory rat. We found evidence of bait shyness following recovery from sub-lethal dosing with two forms of calciferol. Use of intubation as well as feeding showed that the response was to the bait carrier rather than to detection of calciferols per se.
Rodents cause significant economic loss to poultry by feeding on poultry feed, contaminating it, damaging eggs, attacking chicks, and transmitting bacterial and protozoan diseases. A year long study was undertaken to generate data on population structure and dynamics of Rattus rattus inhabiting poultry. Peak density was observed during summer (April). Although rats bred throughout the year, maximum breeding occurred in December (winter). Adults were preponderant and sex ratio tilted slightly towards females. The calculated annual productivity of female R. rattus was 69.59 young/female/year. The continuous availability of food and ample shelter well protected from predators and immigrants indicates behavioural regulation of population. The winter breeding contributed to summer peaks and the female preponderance could be due to dispersal of males.
Twelve mouse traps described and figured by Leonard Mascall in 16th Century England are illustrated and interpreted afresh. Special attention is given to one that is also depicted on the Merode altarpiece, an important 15th Century Dutch painting. Since Mascall's era many of his mouse traps have virtually disappeared. Others have been made more effective by various design changes, including the incorporation of small powerful helical springs and improved release mechanisms, and by the greater use of wire mesh and sheet metal.
A proactive (rather than reactive) approach to rodent control includes effective planning, administration, and coordination. Centralized coordination, detailed scheduling, and well-defined contract specifications provide a solid basis for managing an integrated pest management program. Documentation and data management help to ensure cost effective and efficient operations. The ability to work with people and bureaucracies is essential for the science of rodent control to be applied effectively in real world situations and for vertebrate pest programs to succeed.
The recent outbreak of raccoon rabies in New York State during a period of unprecedented fiscal constraints presents an emerging organizational dilemma− how to handle increasing demands for services in an environment of diminishing resources. As one response to this need, the New York State Department of Health (DOH) is developing an interactive computer system for integrating public education, professional training, and public/professional communication. The basic objective is to enhance consumer access to information regarding rabies, Lyme disease, and other public health issues; thereby, forming the basis for prevention. In essence, this effort can be classified as an "educational intervention," the essential component in any successful program of integrated pest management. The system is comprised of networked computer kiosks distributed statewide in convenient locations to maximize public or professional access. Hardware for each kiosk includes a Macintosh computer, modem, and printer. Each kiosk provides a common database via a series of interactive files regarding biological and disease management information, and with various levels of multimedia development (text, audio, animation, and video). In addition, kiosks provide a directory of government regulations, publications, and services, including geographically defined data. The user can rapidly gather information from a variety of on-board kiosk resources, and can also electronically mail or fax specific queries to appropriate authorities elsewhere. The system is designed to achieve ultimate flexibility, utility and relevancy while being informative and entertaining.
Good Laboratory Practice (GLP) guidelines were implemented by the U.S. Environmental Protection Agency in August 1989. The purpose of the standards are to ensure the integrity of laboratory and field studies which are conducted in support of FlFRA permits and pesticide registrations. Since the advent of GLP requirements, the cost of conducting field trials has increased 40 to 200%, depending upon the type of study. The increased expenses associated with laboratory and field testing, coupled with reregistration expenses, and annual EPA and state registration maintenance fees, have placed a tremendous burden on smaller companies in the U.S.
Use of microcomputers for randomly assigning animals to treatment groups, formulating baits, and keeping records
A computerized laboratory animal tracking database system and several interactive microcomputer application programs for monitoring captive animals, selecting and randomly assigning animals to treatment groups, formulating baits, and other tasks are described.
A wide variety of chemicals including dyes, stains, inks, drugs, fluorescent and non-fluorescent particles, and radioisotopes have been used as markers to identify free-ranging mammals and birds. Markers are useful for studying: (1) home ranges, migration patterns, and population dynamics; (2) bait acceptance, palatability, and exposure of target animals via different baiting techniques for delivering toxicants, chemosterilants, or vaccines; and (3) exposure of non-target animals to control techniques. Five general classes of markers with specific marking capabilities are available for use: (1) dyes, stains, and inks that may be either fluorescent or non-fluorescent which stain the gastro-intestinal tract and its contents, urine, fecal droppings, or hair; (2) inert particles, either fluorescent or non-fluorescent, that can be detected in the gastro-intestinal tract and feces, and can be applied with an adhesive spray to birds' feathers; (3) tetracyclines that can be detected as a yellow fluorescence in bones and teeth; (4) blood markers that can be detected in the plasma or sera (e.g., iophenoxic acid or mirex); and (5) radioisotopes that have various patterns of tissue distribution depending upon the isotope used.
Rodents, both commensal and wild, serve as reservoirs for a variety of diseases in nature communicable to man. Forty-six percent of the 30 human plague cases in the past two decades in California are associated with campgrounds and public use recreational sites. In addition, human cases of tularemia, giardiasis, relapsing fever, Rocky Mountain spotted fever, Colorado tick fever, and Lyme disease have been associated with recreational activities. Commingling of humans, wild rodents and ectoparasites in disease endemic areas places the public at risk from the above-mentioned diseases. Construction of recreational sites without knowledge of wild rodent and disease ecology may enhance rodent and ectoparasite densities and increase disease potential. Cooperation between vertebrate pest specialists, vector ecologists, and public landuse and recreation specialists is needed in the development and management of campground and public use recreational areas. Knowledge of disease awareness and management technology would result in improved disease prevention and better public health protection.
The principal objective of this study was to determine when during the year the control of bandicoot rats would be most cost-effective under the agricultural conditions existing in Bangladesh. An annual cycle in the rise and fall of burrow density was found. This argues for a management strategy directed at reducing rat damage at a specific time period within the year as opposed to a strategy of continuous population reduction. A model predicting rat damage was developed based on monthly estimates of burrow densities in rice and wheat; and projected losses were compared among the four major cereal growing seasons (aman, boro, and aus rice, and wheat). The net benefit of control is predicted to be greatest during the aman rice season in both of the major agroecosystems occurring in Bangladesh.
The Secretariat for Rural Development of the State Government of Chiapas, southern Mexico, has been charged with conducting a campaign against the field rat which began in February 1991. Four areas were identified as key sites for the campaign benefiting 3,355 farmers in a total area of 8,000 ha and an initial budget of approximately $500m Mexican pesos (US$170,000). The major crops for which damage is reported are maize, sugar cane and cacao. The term "field rat" is a general one encompassing any rodent causing damage to field crops and in Chiapas probably covers a variety of species; no studies have been done to identify the species or quantify losses to crops. Personnel had no previous experience in rodent control and no resources to permit preliminary investigations in the field. A method for assessing field damage levels was developed and fields were treated with zinc phosphide (high damage), diphacinone (medium damage) or untreated (low or no damage). A decrease in subsequent losses was reported by farmers involved in the campaign. The campaign in 1992 is restricted by financial and logistic constraints as the field rat campaign has been united with locust and other field pests in a single campaign entitled "Control of Pests to Basic Crops" with a much reduced budget overall. Problems found in the 1991 work and the limitations and of the campaign are discussed.
Roof rats (Rattus rattus) damage an estimated 5-10% of the annual macadamia nut crop in Hawaii, resulting in farm value losses of between $2-4 million. The Denver Wildlife Research Center field station in Hilo, Hawaii studies the biology, impact, and control of rodent pests in Hawaiian agricultural crops. This paper describes field and laboratory research currently being conducted to address rat problems in macadamia nut orchards.
Bandicota bengalensis, a predominant species inhabiting irrigated fields is a potential pest on agricultural crops and is known to live in extensive burrow systems. The burrow opening covered with mud which is an indicator of its activity seems to be discontinuous. An analysis of burrow systems and their occupations indicated reuse of abandoned burrow systems by new entrants. A study simulated in semi-natural conditions supported the view that there is occupation of old burrows by new immigrants. Non-effective barriers, and availability of Panicum repens on bunds, a food alternative, may support the population influx. Availability of old burrow systems due to chemical control and natural predation often result in a ready made habitat for the immigrants and new recruits to reinfest the irrigated fields. Total dismantling of the burrow system and agricultural practices in irrigated field retards the reinfestation.
This paper discusses the development of site-specific baiting technology for controlling the house mouse (Mus musculus) in confined swine facilities utilizing specific rodenticide formulations, bait stations, and baiting strategies. Behavioral research was also conducted to identify primary nesting and travel activities of mice within grower-finishing units. The rodenticide bromadiolone in a block formulation was found to be effective in most baiting trials, and provided resistance to the harsh environment of the swine facility and the necessary versatility for securing baits to minimize hazards to swine. A commercially available tamper resistant bait station was found to be effective for floor baiting procedures in high swine activity areas, and a homemade pvc tube baiter was effective for off-floor baiting efforts. To prevent population resurgences, baiting strategies within grower-finishing units must be responsive to structural and environmental factors affecting the activities of the rodent populations. In the grower-finishing units and other high swine activity areas, both floor and off-floor baiting programs are recommended.
House mice (Mus musculus) cause a variety of problems with livestock, feed, and structures. Researchers have yet to discover an insulative material that is not susceptible to house mouse damage. In this study, house mice caused significant (P < 0.01) increases in the thermal conductance of 10.2-cm thick wall panels insulated with cellotex, fiberglass, rockwool, styrofoam, and vermiculite. Mouse populations increased 3-to 4-fold inside the insulated panels during the 6-month study period.
Rodenticide options for pocket gopher control are more limited now than anytime in the last 40 years. Strychnine remains the most economical and efficacious of the rodenticides available for use in production agriculture and forestry. The anticoagulant rodenticides, diphacinone and chlorophacinone, provide the best alternative to strychnine where the latter is thought inappropriate (e.g., school grounds, parks, etc.). The development of a behavioral type resistance to strychnine baits is currently jeopardizing control on certain ranches. Perishable baits (e.g., cubed raw carrots) are no longer an option because technical or concentrated strychnine is no longer registered for such uses. The development of the gopher burrow builder revolutionized pocket gopher control and has led to widespread extensive and concentrated gopher management which has been successful beyond expectations. Sources of gopher machines, reservoir-type baiting probes, and traps are provided along with a discussion of their uses. Fumigants and other gopher management methods are mentioned briefly.
Data for this report were gathered from three different contractors working on a service contract for the Butte Falls Ranger District of the Rogue River National Forest in southwest Oregon to control pocket gophers (Thomomys spp.). Other data were collected from formal open-hole inspection plots. These plots were also the basis for payment on this contract. Issues of concern on this project were: 1) Production. Could we treat enough acres of the high-risk plantations in the City of Medford Municipal Watershed; 2) Control effectiveness. Could we reach a control comparable to strychnine-treated grain; 3) Cost effectiveness. Would bid prices be low enough to treat enough acres without depleting our budget; and 4) Effect on nontarget species.
Field efficacy evaluation of diphacinone paraffin bait blocks and strychnine oat groats for control of forest pocket gophers (Thomomys spp.)
The effectiveness of bait and the effectiveness of operational baiting were both evaluated for controlling forest pocket gophers (Thomomys spp.) with strychnine oat groat bait and diphacinone paraffin block bait. Radio-telemetry monitoring and recovery of pocket gophers showed that control of individual pocket gophers 1 month after baiting was 72% for strychnine bait and 62% for diphacinone bait. Reduction in pocket gopher activity from operational baiting was based on censusing activity in sample plots. After 1 month the reduction in activity was 61% for strychnine oats and 36% for diphacinone blocks. Bait blocks implanted with radio transmitters were extensively moved and fed on by pocket gophers. Pocket gopher activity was not significantly reduced by either treatment 6 months or 1 year after baiting.
A laboratory study of 68 Botta's pocket gophers (Thomomys bottae) was carried out to compare the preference for 20 different nontoxic baits and the preference and efficacy of 14 different toxic baits. All baits were designed to be more durable (i.e., longer lasting) than loose grain baits to increase the chance that one baiting might successfully control any new gopher invader that moved into an unoccupied burrow system. Bait types ranged from pure paraffin cubes polyethylene bags of grain bait (plain or coated with paraffin and carrot powder), and paraffin grain baits (3.4 g and 10 g). Wide differences were found in bait preferences and in the mortality achieved by the various baits, but generally the bagged baits outperformed the others tested. Some gophers appeared to develop a tolerance for strychnine but bait shyness was not indicated. After being buried 5 months in the field, bag baits and pure paraffin blocks were in good condition, and microwaved whole wheat paraffin baits were only moderately moldy; but paraffin baits containing wheat, ground oats, microwaved oat groats, or carrot powder were mostly mildewed after 1 month underground.
Field trials were conducted to test the effectiveness of a gas exploding device called ''Rodentorch" in reducing pest populations of ground squirrels and prairie dogs. Ignition of a propane/oxygen mixture injected for 30 seconds into burrows reduced prairie dog activity 13.0%. Doubling the injection time in prairie dog burrows to 60 seconds resulted in a 63.3% reduction. Reduction in ground squirrel activity was 40.6% after a 45 second injection time. Comparative trials on ground squirrels using EPA registered gas cartridge and aluminum phosphide fumigants resulted in 90.8% and 83.7% reduction in activity, respectively.
An industrial hygiene study was performed monitoring levels of phosphine gas workers are exposed to when applying aluminum phosphide tablets to rodent burrows. Clothing and gloves were monitored for phosphine gas from residual dust. Air in the breathing zone was monitored with short and long term monitoring equipment. No levels of phosphine exceeding the legal permissible exposure limits (PEL) was detected and although residues were detected on clothing, the levels were usually quite low and dissipated in open air to undetectable levels within 12 to 17 hours in all but a few cases. Hand application was also compared to a mechanical (closed system) type application device which resulted in significantly lower phosphine exposure.
A field efficacy study was completed using Wilco Ground Squirrel Bait (containing 0.005% chlorophacinone) to control California ground squirrels (Spermophilus beecheyi) in Madera County, California. Bait was applied in plastic stations at the rate of 2 lbs. per station. Two plots with buffer zones were treated (about 11.5 acres each). Visual and burrow counts were used as the census indices to determine field efficacy. Pretreatment and posttreatment census observations were conducted over three days pretest and three days posttreatment. Efficacy after 21 days was 94.4% for plot T-1 and 100% on plot T-2 using visual counts. Burrow count data was similar with the T-1 efficacy of 95.1% and T-2 of 95.8%. Tissue residue analysis was completed on muscle, liver and gut remains in recovered ground squirrels and non-target wildlife. Partial carcasses of two cottontail rabbits were found on the plots. Turkey vultures were observed on the study area daily. The numbers and size of vultures observed and the quantity of dead squirrels recorded on the ground surface would tend to indicate no significant impact on the vulture population nor on other wildlife in the treatment area.
Acrolein (Magnacide® H) is currently registered in California as an aquatic herbicide. Field tests were conducted to evaluate its efficacy as a ground squirrel burrow fumigant. Treatments consisted of applying either 20 cc or 40 cc of acrolein (92%) per burrow opening with a specially constructed probe connected to a hose which ran to a cylinder mounted on a pickup truck. The burrow opening was plugged at the time of the application. Burrows in the control plot were plugged in the same manner. Dig-outs and open burrows overlooked during the initial application were re-treated the following day. Both rates of acrolein showed a substantial reduction in the ground squirrel population, in excess of 90%, when adjusted for changes in the population in the control plot. The results appear very encouraging with further field testing warranted.
A laboratory study was conducted in which tissues from zinc phosphide-killed black-tailed prairie dogs (Cynomys ludovicianus) were fed to domestic ferrets (Mustela putorius). Prairie dogs were fed a 2.03% zinc phosphide bait and upon death, two tissue complexes were prepared: stomach, liver, and intestines, and the remaining carcass. Five male and five female ferrets were each fed one of the two treated tissue complexes. A similar number of ferrets were each fed one of the two control tissue complexes. No poisoning symptoms or emesis were observed and no ferret mortality occurred. Zinc phosphide residue was determined in 10 prairie dog carcasses; 99.9% was found in the stomachs and small intestines. Residues were also detected in the large intestine, caeca, kidneys, and gall bladder/liver, none were found in the lungs, heart, or muscle. The low amounts of zinc phosphide remaining in the carcasses, the absence of ferret mortality, poisoning symptoms or emesis, despite the emetic properties of zinc phosphide, confirm that the risk of secondary poisoning from zinc phosphide is unlikely.
Field efficacy evaluation of pelleted strychnine baits for control of mountain beavers (Aplodontia rufa)
Radio-telemetry evaluation of several concentrations of pelleted strychnine bait in earlier tests indicated moderate to good bait efficacy for control of mountain beavers. Evaluation of operational baiting with 0.0%, 0.15%, 0.50%, and 0.90% strychnine bait pellets was made in 1990 and 1991 on 24 reforestation units in Washington and Oregon. Results of baiting monitored with burrow activity indicators showed there was little difference in reduction of activity among treatments. Chemical assays and pen bioassays showed baits were lethal, but ingestion was often delayed or baits were discarded. Reexamination of test plots 1 year after baiting showed no detectable change in activity among treatments.
Operational application of diversionary food in young lodgepole pine forests to reduce feeding damage by red squirrels
The use of diversionary food is an ecological method to reduce feeding damage by wildlife to forest and agricultural crops. The red squirrel (Tamiasciurus hudsonicus} feeds on the vascular tissues of young lodgepole pine (Pinus contorta var. latifolia) and this damage is particularly severe in intensively managed stands. Aerial application of sunflower seed on an operational scale significantly reduced damage by squirrels. This result was achieved in three different ecological zones in the interior of British Columbia, Canada. The food shortage apparently experienced by these rodents during the May-June damage period can be accommodated by an artificial food source such as sunflower seeds. Cost of this operational program is $0-$45/ha and is a worthwhile expense even if required annually for 5-10 years to protect the $2,000+/ha invested in intensively managed pine stands. Adaptation of this technique is discussed with respect to understanding the sociological aspects essential to successful application of research results.
Increasing community awareness of the moral and animal welfare issues associated with conventional pest animal control has focussed interest on non-lethal alternatives, such as fertility control. In Australia, animal welfare organizations have proposed fertility control as a solution to pest problems with feral horses and kangaroos. Wildlife damage control achieved by non-lethal, non-toxic and humane means would have wide appeal and application. Importantly, assessments of effectiveness must focus on damage control, rather than fertility control, per se. Most tests of fertility control drugs and techniques examine effects on reproduction, rather than on population dynamics. Many tests and models have not been robust enough to allow clear conclusions about the usefulness of the technique in damage mitigation. The present role of fertility control in wildlife management in Australia is extremely limited. Its longer-term potential will depend on the successful outcome of future research, development and extension. It also requires an assessment of the economic, environmental and welfare implications of using fertility control for wildlife management. The main barrier to the use of fertility control to manage pest animals is the lack of delivery techniques suitable for widespread and abundant animals. If drugs become available that cause permanent infertility with a single dose, or if current research leads to a technique for the passive spread of anti-fertility agents via infectious organisms, the potential for population management by fertility control for some species, such as foxes, will be increased. No such drugs or techniques are currently available.
Possum control in New Zealand is dependent on the use of sodium monofluoroacetate (1080) and cyanide. Although 1080 is highly effective, its use is restricted to government staff. Cyanide is available for a wider group of licensed operators, but cyanide "shyness" reduces its effectiveness. An acute toxicity programme has been set up to identify non-anticoagulant toxins that could be used safely by farmers. Dose-ranging studies showed that possums are susceptible to cholecalciferol, calciferol, gliftor, alpha-chloralose, and nicotine, but not to bromethalin. As lethal doses for these toxins have been ascertained, which of them are likely to be cost-effective and safe alternatives to 1080 now needs to be established. Bait palatability and field studies will then be undertaken with the most promising candidates.
In parts of New Zealand the beef and dairy industry is being threatened by possums spreading bovine tuberculosis to cattle. As a result new strategies for the long term control of possum populations have been developed. For these strategies, management plans are prepared which detail the control programme for each area. New control strategies are being developed which include long term annual control to reduce infestation of treated areas. Research is being increased in an attempt to find long term answers with improved control techniques and more importantly the possibilities of biological control. Central and Local Government are providing long term funding for these management plans.
Animals in Australia vary greatly in their sensitivity to 1080 poison, with known LD50's ranging from 0.11 to over 800 mg kg-1. Many native species, particularly in western Australia, have evolved tolerances to 1080 through ingestion of native plants that contain fluoroacetate or prey that consume those plants. Despite this, some native species, particularly a few herbivorous mammals, birds and rodents, could be poisoned during control campaigns against vertebrate pests. Field studies indicate that poisoning campaigns are not significantly affecting populations of common non-target animals, but further impact studies are required on vulnerable, rare, endangered, or uncommon species.
A microcomputer software package (AUSPLAGUE) is being constructed for development and testing of management plans for eradicating an outbreak of foot and mouth disease (FMD) in the Australian Capital Territory (ACT). It will indicate when and where control of feral pigs (Sus scrofa) is necessary to contain and eradicate the disease. The software simulates the distribution and prevalence of FMD in feral pigs from the start of an outbreak and throughout the subsequent eradication campaign. The procedure is to integrate landscape data, the distribution and social behaviour of feral pigs, a model of disease dynamics, and appropriate control measures. The modular package design enables data bases and models of host-disease dynamics to be updated as further information is acquired on feral pig ecology. When completed, AUSPLAGUE will be used as a decision-support system in developing control strategies for a wide range of outbreak scenarios, and it will serve as a prototype for other diseases of feral animals and native wildlife.
I examined historical records of unprovoked attacks by cougars on humans in the U.S. and Canada during 101 years (1890-1990). There were 9 attacks resulting in 10 human deaths and at least 44 nonfatal attacks. In a recent paper, I listed these attacks and discussed them in considerable detail (Beier 1991). Although extremely rare, attacks on humans have increased markedly during the last 2 decades, during which cougar numbers and human use of cougar habitats have increased. There is no substantial evidence that habituation underlies this increase in attacks. The data provide weak support for the notion that an attacking cougar may be disposed to attack humans again. Warnings apparently do not deter people from visiting parks in cougar habitat.
The use of cage traps to capture mountain lions (Felis concolor) has the potential to become a valuable tool in the USDA-APHIS-ADC program. Because of California public sentiment, many of the traditional methods can no longer be used or are being severely restricted. Due to increasing requests for assistance, California ADC personnel have had to develop a method that will be highly selective, humane, and effective in rural and urban areas. The development of the mountain lion cage trap and its applications are described.
To improve feral cat control we developed a dry pelleted toxic bait and evaluated the potential of lures. A polymer fish meal bait was preferred by cats from a range of bait types tested. L-alanine further increased bait acceptance by cats in pen trials and catnip may have the potential to increase field acceptance and target specificity. An oral LD90 of 0.38 mg/kg was established for sodium monofluoroacetate (1080) in feral cats voluntarily eating surface-loaded baits. Acute toxicity to cats of warfarin, cholecalciferol, and gliftor was tested. However, because the cat proved highly sensitive to 1080, we recommend its use at a dose of 2 mg per cat bait. In preliminary field trials of bait acceptance using non-toxic polymer bait (without flavours or attractants), marked with the plasma marker iophenoxic acid, 50% of 39 cats caught within 3 weeks of laying the baits were marked. Subsequently polymer bait, surface coated with 1080 was used in the successful eradication of feral cats from Matakohe Island (37 ha), Whangarei Harbour, New ZeaJand.
Feral goats (Capra hircus) and feral sheep (Ovis aries) occur on numerous islands throughout the world and cause severe damage to island resources. Damage includes large-scale alteration of plant communities, negative impacts on insular endemic species of plants and animals, and damage to soils and cultural resources. Complete eradication is the best solution to the problem. Proposed control techniques include poisons, predators, diseases, sterilization, trapping, and shooting from the air, but experience shows that shooting from the ground, combined with the use of dogs, Judas goats, and perhaps fencing, is the best approach in most cases. Successful control programs have recently been completed or are nearly completed on the islands of Hawaii, San Clemente, and Santa Cruz.
The goat (Capra hircus) was first introduced into Western Australia (WA) over 100 years ago and since this time have been liberated and become feral. Feral goats are now found over much of the semi-arid and arid pastoral areas of the State and as uncontrolled grazers cause significant damage to the rangeland. The use of commercialisation as a control strategy to induce landholders to reduce feral goats has been used. This strategy is appealing for several reasons. It requires little government involvement from agencies responsible for pest control, resulting in low public costs. It returns immediate, tangible profits to landholders for the control effort and it utilizes the pest as a resource, making the programme more acceptable to some individuals. However, it is now clear that a commercialisation policy has not been successful in reducing overall feral goat numbers and the consequent damage. Some reasons for this include; commercialisation requires the creation of an infrastructure to handle the product; immediate economic returns from feral goats become long-term cash flows; long-term benefits are not considered; individual control is undertaken rather than co-operative programmes; feral goats are not included as part of the landholders domestic stocking rate entitlement. If such a policy is to continue it will not achieve the long-term objective of eradication. A feral goat eradication programme has recently been instigated in Western Australia by the pastoral industry. Although, commercialisation is to be used to remove the bulk of the population, such a strategy cannot be used on a long-term basis and follow-up control must be undertaken if the objective of the programme is to be achieved. The prolonged use of a commercialisation policy will result in the preservation of a species rather than the elimination of it.
Electronic frightening devices for reducing coyote predation on domestic sheep: Efficacy under range conditions and operational use
A portable 12-v battery-operated coyote frightening device was developed for reducing coyote predation on sheep and evaluated on fenced pasture farm flock operations (1979-1982). In 1986, the final experimental model consisted of a PVC case, a timer, a blinking strobe light, and a warbling type siren that was activated for 7-10 seconds at about 6-7 minute intervals throughout the night. The devices were generally suspended about 2 m above the ground and were activated at dusk by a photocell and turned off about 2 hours after dawn by a timer. Here we report tests on high mountain summer sheep ranges (1982-1987), evaluation of the devices by ADC and external cooperators (1987-1990), and efforts to make the devices commercially available. On high mountain summer range, the devices reduced sheep losses on average about 60% with a mean dollar value savings of lambs of over $2,400 per sheep band. In the operational evaluations, 84% of our cooperators indicated that coyote predation on lambs was lowered when devices were used. Manufacture and sale of the device under the name ''Electronic Guard" was begun in 1991 by the ADC Program's Pocatello Supply Depot.
A field study to evaluate the performance of 3 types of coyote traps (No. 3 Soft Catch® coil-spring, No. 3 NM long-spring, No. 4 Newhouse long-spring) was conducted in south Texas in January and February 1991. Tests were designed to determine capture efficiency, extent of injury and effectiveness in excluding nontarget species. Results showed a capture rate of 100% for the 3 NM and No. 4 Newhouse, and 95% for the Soft-Catch. Soft-Catch traps caused the least injury to captured coyotes. All trap types were equipped with pan tension devices and were successful in excluding most small nontarget species.
Predation by coyotes (Canis latrans) upon domestic sheep is a serious economic problem for some sheep producers in the United States. One of the few depredation control techniques that has been quantitatively analyzed is denning, the process of removing pups from the dens of depredating coyotes. The significance of coyote prey selection and terriioriality are discussed with regard to the efficacy of denning and possible future depredation management strategies.
Vomiting is a characteristic, although undesirable effect when using Compound 1080 (sodium monofluoroacetate) as a method of predator control for coyotes. Compound 1080 meat baits with (treatment) and without (control) an antiemetic, metoclopramide hydrochloride (MH), were fed to captive coyotes to determine whether MH would prevent vomiting. All treatment and control animals died as a result of consuming the 1080 bait with no difference between the groups in time from bait consumption to death. There was no significant difference between the number of treatment and control animals that vomited after consuming the baits. Likewise there was no difference between the treatment and control groups in the time from consuming 1080 to vomiting, the duration of the vomiting period, or the number of times each animal vomited. Despite indications in the literature to the contrary, MH did not prevent 1080-induced vomiting in coyotes.
The acute oral LD50 of Compound 1080 to magpies was estimated at 1.78 mg/kg indoors, 1.91 mg/kg outdoors in summer, and 2.30 mg/kg outdoors in winter. Postmortem 1080 residues were detected in 75 of76 treated birds. Higher doses yielded higher 1080 residues. Within dose levels, birds surviving longer carried lower residues. In a separate test, an average residue of 0.09 ppm was found in 8 birds treated at 1.59 mg/kg and euthanized 24 h post dosing. The adjusted dietary LC50 of Compound 1080 to magpies tested indoors was estimated at 16 ppm. During LC50 tests, the influence of 1080 on food consumption and bird weight varied. Birds receiving low doses were unaffected and those receiving high doses died quickly. Birds that were affected but did not die quickly, usually lost weight but only slightly reduced food intake. All birds that died had detectable 1080 residue in breast muscle. Birds fed higher 1080 dietary concentrations probably exhibited higher residues postmortem. Our adjusted average LD50 (2.12 mg/kg) appeared somewhat higher than reported in the literature; nonetheless, magpies are very sensitive to 1080. No sex differences were noted. Age, metabolic influences, or cold temperatures might explain the high LD50 value estimated for winter. The detection of 1080 residue in tissue samples is a useful tool for assessing 1080 exposure in magpies−but it might not be unequivocal.