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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.


Blurred images: and the future of wildlife damage management

The paper points out a number of perceptions that blur and damage the image of wildlife damage management and their importance to the future. Some of the reasons for the perceptions are suggested and a number of steps suggested to improve the public image. It concludes on a note of optimism for the future.

Charting a future: Process and promise

The Animal Damage Control program has been heavily involved in strategic planning since its transfer from USDI to USDA. The first effort was undertaken in 1989 by the program's management team. It was an introspective, critical look at what changes were needed to improve the program's strategic position in the natural resources community. That plan failed to achieve the desired objective due principally to the lack of involvement by ADC employees and others outside the program. In 1991, a more comprehensive effort was begun known as "Futuring." In this process, a representative from each organizational level of the program and representatives from wildlife management organizations formed a Futuring Committee. The analysis and recommendations of this group were the basis of the new ADC strategic plan. The involvement of employees and other interests made this effort far more successful in giving the program strategic alignment with the natural resources community.

Monitoring wildlife damage management pesticides, the role of the California Department of Fish and Game

The Pesticide Investigations Unit (PIU) of the California Department of Fish and Game is responsible for identifying and mitigating the hazards of pesticides to fish and wildlife. By conducting annual reviews of individual county vertebrate pest control plans, investigating pesticide related fish and wildlife losses and reviewing all pesticides proposed for registration in California, the PIU monitors potential effects of vertebrate toxicants on fish and wildlife. The California Department of Fish and Game is working in conjunction with other state and local agencies, manufacturers and applicators to develop balanced, safe pest control programs which provide maximum protection to California's fish and wildlife.

Trends in mountain lion depredation and public safety threats in California

The mountain lion (Felis concolor) is widely distributed in California over at least 80,000 square miles of a variety of habitats. Trends in lion damage to property and threats to public safety have increased in recent years. The Department of Fish and Game has documented confirmed damage to property caused by lions since 1972. In 1972, there were four depredation permits issued and one mountain lion taken, while in 1993 there were 192 permits issued and 74 lions taken. Four verified incidents of mountain lions injuring humans have occurred in California since 1985. All four incidents involved children and none was fatal. Although difficult to verify, public reports of lion sightings are increasing, apparently as a result of increasing lion numbers and an expanding human population using lion habitats.

Food habits and management of introduced red fox in southern California

Introduced red fox in urban Orange County, California ate a wide variety of foods. Mammals and birds were consumed at all times of the year and both taxa appeared in approximately half or more of the fecal samples at all times of the year. Human supplied food remains were also common and supplemental feeding occurred at all study sites. Supplemental feeding has the potential to exacerbate problems for management of introduced red fox and several endangered species.

Feral cat control in Britain; Developing a rabies contingency strategy

Feral cat (Felis catus) control is required for reasons of public health, the welfare of cats themselves, and rabies control should an outbreak occur in Britain. A prerequisite to the control of feral cat colonies would be establishing their location. A method for locating colonies was developed and tested in four urban areas with a mean area of 157 sq km. Each area was surveyed on foot and by car to obtain the number and distribution of feral cat colonies. The method involved making inquiries at premises most likely to be frequented by cats ("high risk areas"). Most (94%) of the 116 feral cat colonies found (comprising approximately 874 cats) were found at the nine high risk categories. Few feral cat colonies occurred elsewhere, confirming that high risk categories were useful in locating feral cats. Information concerning the efficacy of cage trapping as a method of feral cat control was also investigated. A wide variety of baits were used in the traps including proprietary dry pelleted cat food, which was considered to be the most effective and was used in all the subsequent trap trials. In a series of 12 field trials, using live capture cage traps, between 82% to 100% of feral cats in the colonies were captured. Altogether 202 cats were captured at a rate of 21 cats per 100 trap nights.

An approach to controlling golden eagle predation on lambs in South Dakota

A case of severe golden eagle (Aquila chrysaetos) predation on domestic sheep was documented on seven South Dakota ranches during the spring of 1993. One hundred forty-two lambs and one ewe were verified as being killed by eagles during a six-week period. In an effort to resolve the depredation problem, padded leghold traps were used to capture 21 golden eagles in or near the lambing pastures. The captured eagles were translocated and released approximately 322 km northeast of the capture area. Predation on lambs ceased following the relocation effort.

Bear relocations to avoid bear/sheep conflicts

Preventive relocation of black bears (Ursus americanus) was tried as an alternative to lethal removal of bears that attacked sheep in northeastern Oregon. Bears in likely problem areas or in close proximity to sheep bands were captured with culvert traps and moved to other ranges without sheep. Sixteen bears were relocated in 1990 and five in 1991 from areas where five damaging bears had been destroyed in 1989. The five bears relocated in 1991 were radio collared and monitored by the Oregon Department of Fish and Wildlife. None of them were involved in livestock depredations subsequent to relocation. Sheep losses to bears were lower in 1990 and 1991 than in prior years when bears were not relocated. Relocation appears to be a feasible alternative to lethal control of black bears that attack livestock. The costs of preventative relocation and killing depredation bears were approximately equal, but relocation was deemed more acceptable to the general public.

Supplemental bear feeding program in western Washington

Black bear (Ursus americanus) damage to trees is a severe problem in the Pacific Northwest. Significant damage has been observed for many years, especially in highly managed private industrial forests in western Washington. The introduction of intensive silvicultural techniques resulted in higher yields, but may have also made trees more vulnerable to black bear destruction. Early lethal control efforts lost public support and the forest products industry investigated different methods that concentrated on non-lethal management tools. In 1985, the Washington Forest Protection Association introduced supplemental bear feeding as a damage prevention program in high damage areas during the spring months. This became a very successful alternative to the earlier methods of killing bears. The supplemental feeding program has great support from land managers and the public as an economically viable additional tool to black bear population control.

Do livestock guarding dogs lose their effectiveness over time?

Information about the effectiveness of livestock guarding dogs for reducing coyote predation on sheep was gathered from livestock producers in the Animal Damage Control Livestock Guarding Dog Program and in Colorado. Eighty-two percent of the producers contacted reported that the performance of their dogs remained the same or improved during 1993 compared with previous years. Eighteen percent of the producers reported a decrease in their dog's effectiveness, but most still felt the dogs were a benefit to their livestock operation. Most producers who noted a decrease in effectiveness attributed it to an apparent increase in the number of coyotes and/or an increase in their predatory activities on livestock.

An evaluation of anti-coyote electric fences

We interviewed 21 sheep farmers and evaluated their electric fences to identify problems and determine efficacy of electric fences to prevent coyote (Canis latrans) predation. Modified woven wire fences and fences of 9 high-tensile smooth wires alternating charged and grounded were most effective in preventing coyote predation. The most serious problems in fence design and maintenance were a) bottom charged wire too high above ground level, b) wires spaced too far apart, and c) inadequate vegetation control.

Field evaluation of chemical attractants for summer use on M-44s

Responses of free-roaming coyotes (Canis latrans) to four chemical attractants (W-U lure, artificial beef liver flavor, artificial smoked fish flavor, and Fatty Acid Scent) used on M-44 tops were measured during the summer months in Colorado, Idaho, Montana, Washington, and Wyoming. Visitation and pull rates varied throughout the study period from area to area and appeared to be associated with weather, food abundance, and coyote densities. Fatty Acid Scent and W-U lure produced the highest visitation and pull rates.

Wolf depredation management in relation to wolf recovery

By 1930, wolves were extirpated from the western United States for livestock protection. In 1973, the Endangered Species Act protected wolves, and by 1980, wolf recolonization began in Montana. Confirmed livestock losses have been 17 cattle and 12 sheep with 16 wolves controlled as part of a program to enhance the recovery of non-offending wolves. ADC has: 1) controlled problem wolves, 2) improved communication with affected publics and governmental agencies, and 3) enhanced wolf recovery in Montana.

Current (1994) ground squirrel control practices in California

Current control practices are discussed for the California ground squirrel (Spermophilus beecheyi) which is considered a major rodent pest to agriculture. The primary control options are poison baits, burrow fumigation and trapping. The effectiveness of baits and fumigants is linked closely with the squirrel's annual life cycle, hence knowledge of their cycle is essential. The elements of the squirrel's life cycle importance to management are given in detail. Habitat modification and other methods useful in select instances are provided, along with control strategies within the context of integrated pest management.

Trapping ground squirrels as a control method

Trapping of ground squirrels could be conducted following the use of fumigants or rodenticides to further reduce populations. Trapping should be considered as an alternative to the other methods of control in cases where other controls have not worked or would not be prudent to use. Trapping can be conducted during a longer period of the year than the other methods. The type of trap used, whether live trap or one of the kill traps, can be selected as to the environmental concerns of the trapper as all traps can be effective.

Ground squirrel management in the Angeles National Forest

In 1987 and 1988 there was a sharp rise in epizootics in the ground squirrel (Spermophilus beecheyi) population in the Arroyo Seco District of the Angeles National Forest. In response to these incidents, a proactive rather than a reactive approach was implemented in this area. This was the beginning of a ground squirrel management program in the Angeles National Forest. From 1988 to 1993 the program developed into a joint management program between the United States Department of Agriculture, Forest Service (USFS), Los Angeles County Department of Health Services (OHS), Los Angeles County Agricultural Commissioner's Office-Weights and Measures (CAC}, and the concessionaires in this area. The number of epizootics has been reduced from seven in 1987 to zero in 1992 and 1993. Cost of field activities related to plague surveillance has been reduced 160%. The program is now being expanded to cover every district in the Angeles National Forest.

California ground squirrels at Concord Naval Weapons Station: alternatives for control and the ecological consequences

This paper presents a methodological approach that was recently developed to determine alternatives for control of California ground squirrels (Spermophilus beecheyi) and the resulting ecological consequences at the Concord Naval Weapons Station (CNWS). The U.S. Navy initiated this study upon determining a need to control ground squirrels for safety reasons. The squirrel's ecological role at CNWS was examined by estimating squirrel abundance and distribution throughout CNWS, analyzing predator diets, and determining the squirrel's relationship to the California tiger salamander (Ambystoma californiense). In addition, the efficacy of live capture and translocation of squirrels as a possible control method was specifically examined using an experimental approach. Finally, alternative control measures are reviewed and discussed in the context of our results. The emphasis of this paper is on the methods employed and the discussion of alternatives as an example of an ecologically-based approach to control programs. As wide-scale poisoning control programs have recently come under public opposition in the courts and otherwise, studies such as these will serve to direct future management efforts toward control programs that consider several alternatives and their ecological effects.

Acrolein as a ground squirrel burrow fumigant

Acrolein (Magnicide ®H) is registered in California as an aquatic herbicide. Studies in Alameda and Modoc Counties were conducted to evaluate the field efficacy of acrolein as a ground squirrel burrow fumigant. Applications of acrolein (92%) at 20 ml and 40 ml per burrow were made from a custom built jet gun connected to a hose which ran to a cylinder mounted on a pickup truck. The burrow openings were covered with soil after application. The application rate of 20 ml of acrolein per burrow provided approximately 90% control of ground squirrels. Acrolein applied at 40 ml did not significantly increase efficacy of the treatment.

Efficacy of five burrow fumigants for managing black-tailed prairie dogs

Current limitations on pesticides for managing prairie dog populations underscore the need for additional research on candidate compounds. I conducted this study to determine the efficacy and cost-effectiveness of two registered burrow fumigants (aluminum phosphide and gas cartridges) and three unregistered burrow fumigants (methyl bromide, chloropicrin, and a methyl bromide/chloropicrin mixture) for managing black-tailed prairie dogs. All five fumigants reduced burrow activity 94% to 97%, as measured by a plugged burrow technique. Total costs for materials and labor for the registered products, excluding application equipment, were nearly twice ($30.00 to $38.50) the cost of the unregistered fumigants ($15.25 to $16.25).

Natural history and protection of burrowing owls

Burrowing owls (Speotyto cunicularia) were monitored over a four year period at Naval Air Station North Island, a developed area at the north end of San Diego Bay, California. Protection of the nest burrows and a burrow marking program were initiated in 1991. The breeding population increased from 14 to 27 nests after this marking program began. Burrow types and ways to differentiate burrows used by owls from those used by California ground squirrels (Spermophilus beecheyi) are outlined. The importance of burrows and their management is discussed with reference to the natural history of the owl.

Activity patterns of the pocket gopher Pappogeomys merriami merriami in a Mexican rangeland

Pocket gophers (Pappogeomys merriami merriami) are a problem in both crops and rangelands of Mexico. In rangelands, damage results from the animals burrowing habits which cause much soil disturbance, and their feeding on rangeland vegetation. Although considered a pest, to date there have been no quantitative studies of the activity and damage caused this species. This study was initiated to document fluctuations in activity of P. m. merriami throughout the year in a Mexican rangeland.

Rodent pests in Colombian agriculture

The tropical zones of Latin America are sources of a great faunal richness. A significant number of mammals are associated with damage to the agricultural and livestock industries of Colombia. Some studies have indicated that rodents cause serious economic and social damage in the agricultural, livestock, and stored product sectors of the Colombian economy. Evaluations of this damage have been based on three criteria: 1) the characteristics of the damage; 2) the species of rodent involved; and 3) the loss of production at harvest. Cereals and oil-producing crops are most affected as standing crops; in the livestock area, poultry and pork production are most affected; many agricultural products, especially grains, are attacked by rodents during the post-harvest stage. The level of economic loss caused by rodents can range from about 4% to about 50% depending on the crop, the season, and the species of rodent involved in the damage. Social damages are characterized by the transmission of illnesses such as salmonellosis and leptospirosis via contaminated foods or grains. Six species of rodents of the families Cricetidae and Muridae are most commonly associated with these problems in Colombia.

Effective period for control of the brown spiny field mouse (Mus plantythrix) in dry land crops

Information on breeding aspects of rodents is important to ensure control program timing necessary for effective pest management. Hence, studies on breeding aspects of the brown spiny field mouse (Mus platythrix), a known rodent pest in dry land crops were investigated including environmental factors influencing reproduction, from regular monthly collections made during the years 1990 and 1991. Field trapped rodents were classified to derive their population structure--percent juvenile, pre-pubertal and adult including prevalence of pregnancy--based on body weights and sexual conditions. The stage of pregnancy and sperm motility were confirmed by autopsy studies. The data were also analyzed to calculate the annual breeding productivity. The results indicate that the brown spiny field mouse experiences a seasonal reproductive cycle of active breeding during the period June to February followed by sexual quiescence during the period March to May. The peak reproductive activity seen during September (55%), October (79%) and November (62%) coincides with peak abundance of heavier males and females in the population. A litter size of two (during June) to eight (during October) also coincides with peak prevalence of pregnancy. The adult male to female ratio is 1.0:1.1, respectively. The annual breeding productivity is calculated to be 54 young/female/breeding season. Further prevalence of rainfall, low temperature, short day length, and higher relative humidity seen during July onwards promoting green vegetation are conducive to reproduction. Hence, it is inferred that the period March to May is suitable for timing the rodent control programs in dry land crops against the brown spiny field mouse, when the field population is at base considering the cost-benefit ratio and operational aspects.

Effects of initial rat captures on subsequent capture success of traps

Trapping records from studies conducted in Hawaiian sugarcane fields were analyzed to determine the effects of rat captures on subsequent capture success of Rattus norvegicus, R. rattus, and R. exulans. Traps that captured rats were subsequently more likely to capture another rat of the same species. We detected no differences in trap responses of males and females, nor did we observe any evidence that capture success of Polynesian rats and roof rats was affected by previous captures of Norway rats. This increased trap success may have been due to residual trap odors, or to greater success of traps set in optimal locations. Researchers should exercise caution in interpreting trapping results, and take precautions to eliminate residual trap odors due to previous captures. A better understanding of the effects of congeneric odors on the trapability of rats could lead to the development of more attractive and selective bait formulations, improved trapping techniques, and better interpretation of research results.

Stowaway transport rates of house mice (Mus domesticus) and deermice (Peromyscus maniculatus)

Stowaway transport rates were obtained from behavioral observations of 14 house mice (Mus domesticus) and 14 deermice (Peromyscus maniculatus) during commercial transport. One house mouse escaped during unloading and flaking of 2,500 kg 2-year old oat hay. Three house mice and two deermice were handcaught on trucks during unloading of 51,110 kg of transported barley straw and grass hay. One house mouse was handcaught after being buried alive in grain. Two house mice escaped during unloading of a semitruck holding dog food. House mice (one live, six recently-dead) and deermice (two recently-dead) were taken from a feedmill screen over which had passed 940,313 kg grain. Ten deermice were trapped in a pickup truck cab. In conclusion, multiplying these transport rates, (7(10-5) house mice per transported kg hay and 7(10-6) house mice per transported kg grain, by the worldwide volume of transported hay and grain implies thousands of stowaway house mice occur. Deermice have comparable transport rates. Experiments (N = 82) were done to determine if a particular sex or age predominates among stowaways. For each experiment, I put one to five hand-caught or trapped house mice in a haybale, let them remain in the haybale for 1 to 13 days, put the haybale in a wheelbarrow, pushed the wheelbarrow for I5 minutes, and then searched for transported mice. Stowaways, mice remaining during transport, included 74 of 115 mice (64%), which were primarily lower weight classes, characterizing house mice coming into reproduction. In conclusion, live stowaways should arrive in >50% infested loads.

Effects of CS2-starch xanthate on consumption by rats

We conducted a series of preliminary feeding trials with Norway rats (Rattus norvegicus), roof rats (R. rattus), and Polynesian rats (R. exulans) to examine the effects of carbon disulfide (CS2 on consumption of nontoxic foods. We formulated CS2 at target concentrations of 10 ppm in deionized water, and of 50 ppm to 100,000 ppm in a starch xanthate matrix. However, we did not analyze actual concentrations of CS2 in the test foods or measure its rate of volatilization, and thus cannot verify the levels of CS2 the rats were exposed to CS2 diluted in water and applied directly to food had no apparent effect on consumption by any of the species. Formulations with 50 ppm CS2 in starch xanthate influenced food choice by Norway rats and roof rats in one test, but not in another. Concentrations ≥ 10,000 ppm repelled Norway rats. CS2-starch xanthate had little effect on consumption by Polynesian rats. Further testing is needed to develop effective formulations and delivery methods for utilizing CS2 as a bait additive.

Present status of Rattus norvegicus on Santa Cruz Island, Galapagos, Ecuador118123

Introduced commensal rodents have had a major impact on the biota of island communities worldwide; the ship rat (Rattus rattus) and the house mouse (Mus domesticus) have a long history in the Galapagos islands, while the larger, more aggressive brown rat (Rattus norvegicus) was identified only in 1983 on one island, Santa Cruz. By 1988 it had spread into the agricultural zone but was still restricted to human habitation. In 1993 the cross-island road and village communities in the agricultural zone of Santa Cruz were sampled using a standard trap line of break-back traps. House surveys were also carried out, where appropriate. The brown rat was found to occur at all sites sampled on the south side of the island, including sites independent of human habitations, and is now the dominant commensal rat in houses. The impact of the brown rat on the ship rat and the conservation implications of its spread are discussed.

Active ingredients in APHIS's vertebrate pesticides - use and registration data

The Environmental Protection Agency's (EPA) reregistration process has had an extensive impact on the Animal Damage Control Program administered by the Animal and Plant Health Inspection Service (APHIS) of USDA. Specifically, the 1988 Amendment to the Federal Insecticide, Fungicide, and Rodenticide Act required a comprehensive reevaluation of pesticide safety; nearly 500 data submissions have been requested by EPA from APHIS to maintain its federal (Section 3) and state (Section 24(c)) low volume minor use vertebrate pesticide registrations. These registrations are used to control damage to American agricultural resources, mitigate losses to selected wildlife species, and reduce threats to public health and safety. A primary function of both APHIS's Denver Wildlife Research Center (DWRC) and Technical and Scientific Services (TSS) office is the maintenance of these registrations containing carbon, sodium nitrate, Compound 1080, sodium cyanide, DRC-1339, PA-14, zinc phosphide, and/or strychnine. APHIS has responded to EPA's data requests in a variety of ways including: requesting waivers, negotiating data requirements, proposing less costly alternatives, monitoring data contracts, and conducting the necessary studies. Since 1989, DWRC and its cooperators have submitted over 250 studies in support of these registrations. This paper will: 1) discuss the active ingredients in APHIS's vertebrate pesticides and their reregistration status; 2) evaluate the effectiveness and cost of each type of response; and 3) provide lessons for the future.

Predicting the outcome of rodenticide trials against Norway rats living on farms

Difenacoum and bromadiolone treatments against Norway rats may fail because: 1) the animals eat little or no bait, 2) reinvasion rapidly offsets any success, or 3) the population contains resistant individuals. By monitoring bait takes and employing independent measures of rat activity such as tracking plates, it is possible to identify, often in the early stages of a treatment, patterns that indicate the contribution of each of these causes to the eventual outcome. If there is no bait take from the majority of bait points visited by rats in the first week then the treatment is unlikely to be successful, no matter how long it continues. Furthermore, treatments carried out on arable farms, where cereals are stored and the environment is relatively undisturbed, are likely to be less successful than those carried out on livestock farms, where alternative food may also be abundant but where the environment is less predictable. Bait takes that persist at the same bait points for longer than 16 days strongly suggest the presence of resistant rats, while immigration may be significantly affecting the treatment if takes recur at more than 30% of points after a period of seven days. Once a given problem has been identified remedial measures can be taken.

Resistance to the first and second generation anticoagulant rodenticides-- a new perspective

Warfarin resistance was first discovered among Norway rat (Rattus norvegicus) populations in Scotland in 1958 and further reports of resistance, both in this species and in others, soon followed from other parts of Europe and the United States. Researchers quickly defined the practical impact of these resistance phenomena and developed robust methods by which to monitor their spread. These tasks were relatively simple because of the high degree of immunity to warfarin conferred by the resistance genes. Later, the second generation anticoagulants were introduced to control rodents resistant to the warfarin-like compounds, but resistance to difenacoum, bromadiolone and brodifacoum is now reported in certain localities in Europe and elsewhere. However, the adoption of test methods designed initially for use with the first generation compounds to identify resistance to compounds of the second generation has led to some practical difficulties in conducting tests and in establishing meaningful resistance baselines. In particular, the results of certain test methodologies are difficult to interpret in terms of the likely impact on practical control treatments of the resistance phenomena they seek to identify. This paper defines rodenticide resistance in the context of both first and second generation anticoagulants. It examines the advantages and disadvantages of existing laboratory and field methods used in the detection of rodent populations resistant to anticoagulants and proposes some improvements in the application of these techniques and in the interpretation of their results.

Registration requirements for non-toxic natural products as animal damage control agents

Plant extracts, animal glandular secretions and excretions, and natural food flavoring agents are common sources of natural products that can be used in animal damage control applications. Such products can be used either by themselves (e.g., coyote urine as a rodent repellent), or in combination with other control agents (e.g., food odor or flavor enhancer at baiting sites). The Environmental Protection Agency registration requirements are described for a variety of potential applications of natural products including bird and rodent repellents. In some applications, the product chemistry or other data requirements could make the registration process prohibitive due to the cost of chemical identification and quantification of compounds. Under a new Reduced Risk Pesticide Program, however, many data requirements for registration of natural products can be waived by EPA with the exception of some toxicology and efficacy studies.

Zinc phosphide: Implications of optimal foraging theory and particle-dose analyses efficacy, acceptance, bait shyness, and non-target hazards

The U.S. Department of Agriculture (USDA), Animal Plant and Health Inspection Service (APHIS) maintains six federal registrations for zinc phosphide (Zn3P2); three of these address the control of eight rodent species using steam-rolled oats (SRO) or wheat grains in diverse applications. Optimal foraging theory (OFT) and "particle dose analysis" (PDA) afford predictions relevant to the efficacy, acceptance, bait shyness, and non-target hazards of these Zn3P2 baits. For PDA, numbers of SRO groats or whole wheat grains associated with acute oral median lethal (LD50) or approximate lethal (ALD) doses of Zn3P2 were compared among nine target rodent and eleven non-target avian species. Key outcomes were: 1) mean (±S.D.) SRO groats and wheat grains weighed 23 (±9) and 18 (±9) mg [assumed to carry ≈0.46 (2.0%) and ≈0.33 (1.82 %) mg Zn3P2, respectively; 2) published acute oral LD50 values for the target rodents ranged between 16.2 and 18.0 mg/kg, with a 42.0 mg/kg ALD cited for the white-footed mouse (Peromyscus maniculatus); 3) estimated minimum-maximum number of SRO groats and wheat grains needed for ingestion of the LD50/ALD doses by target species were 1.6 to 39.1 and 1.7 to 3.8, respectively; and 4) estimated minimum-maximum number of SRO groats and wheat grains associated with primary LD50/ALD hazards to nontarget avian species were 1.3 to 175.8 and 1.8 to 245.1, respectively. Theoretical implications of OFT and PDA to efficacy, acceptance, bait shyness, and specificity of Zn3P2 baits in rodent control are provided; the potential effects of food-handling time, bait-search time, predator density, social-dominance hierarchy, food-intake pattern, and bait-distribution pattern are discussed.

Contracts and registration studies

Public and governmental concerns about the health, safety, and environmental impacts of pesticides have led to increased regulatory requirements to determine the hazards and risks associated with their manufacture, distribution, and use. Vertebrate pesticides are regulated by the U.S. Environmental Protection Agency (EPA) under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), as amended. Much of the data required for registration of these pesticides will be generated by commercial testing laboratories under contract to the product registrants or sponsors. In this paper, we address aspects of the contract research process including: 1) an overview of FIFRA requirements, 2) the nature of the contract research process, 3) guidelines for setting up and administering a contract for this type of work, and 4) several case studies to illustrate some of the "pitfalls" that may be encountered. The information presented is based on the collective experience of the authors' involvement with 49 contracted studies over a three-year period.

Assessment of toxic bait efficacy in field trials by counts of burrow openings

The Levant vole, Microtus guentheri, is a pest of most of the field crops in Israel. It lives in gallery systems, the openings of which are clearly visible, and is active above ground mainly at night. Its activity was assessed by plugging the burrow openings (holes) and, after three nights, counting the number of reopened holes. The efficacy of control by whole wheat toxic baits was determined by counting the number of reopened holes before and after the treatment in random squares. Three chemicals were tested: sodium fluoroacetate, zinc phosphide and brodifacoum. The bait was applied either by hand, airplane, or centrifugal spreader. The period between treatment and post-treatment count was one week for the two acute rodenticides, and at least two weeks for the anticoagulant baits. Satisfactory results were obtained: 1) by a 2% zinc phosphide bait, with 0.7 g inserted manually into the voles' holes, or distributed at rates between 4.2 to 12.2 kg/ha; 2) by a 0.05% sodium fluoroacetate bait, with 0.2 g being inserted manually into the holes, or distributed at rates of 1.6 to 4.0 kg/ha; and 3) by 0.005 % brodifacoum bait, with 3 g being inserted manually into the burrows, or broadcast at rates of 5.8 and 8.7 kg/ha.

Laboratory and field assessment of a carbon monoxide producing fumigant cartridge for use in the control of rabbits (Oryctolagus cuniculus)

Fumigation is the most effective method of rabbit (Oryctolagus cuniculus) control available in the United Kingdom. Use of current methods, involving formulations that generate hydrogen cyanide (HCN) or phosphine (PH3) on exposure to moisture, is limited by weather conditions. A carbon monoxide producing cartridge has been developed which can be used independent of weather conditions. The cartridge is similar in size to the smaller carbon monoxide (CO) cartridge used in the United States, but produces up to 70% more CO. High concentrations of CO were measured at the entrances of an unoccupied artificial warren fumigated with CO-cartridges, but these declined quickly. There was relatively little movement of CO through the warren but in most parts concentrations of ≥1% were maintained for one hour or more. Wind speed and direction were shown to have significant effects on CO concentration and distribution.

Racumin Plus, a new promising rodenticide against rats and mice

Coumatetralyl (Racumin®) has been known since 1957 as a multiple dose anticoagulant and has been used successfully over many decades. In the seventies and especially the eighties, rats developed an increased resistance to anticoagulants in certain regions of Central Europe. Also, the addition of vitamin K to animal feed (especially to chicken feed) has reduced the efficacy against rats and mice in farm buildings. Combinations of anticoagulants with different types of vitamin D are generally described to increase the efficacy of action against rodents. It was found that especially the combination of coumatetralyl with cholecalciferol (vitamin D3) could overcome the above mentioned problems. Cholecalciferol causes hypercalcemia and, therefore, has a different mode of action compared to anticoagulants. The combination of these active ingredients leads to an obvious increase in efficacy against rodents, even under difficult conditions. The formulation with optimal rodenticidal efficacy contains 0.04% coumatetralyl and 0.025% cholecalciferol mixed in rolled oats.

Hantaviruses and their rodent reservoirs in the United States

Since 1993, three novel hantaviruses have been identified from the United States of which at least two can cause a severe respiratory disease termed hantavirus pulmonary syndrome (HPS). Rodent reservoirs have been identified for two viruses; Peromyscus maniculatus is the primary host of Muerto Canyon Virus (MCV) in the western United States and genetic analyses have implicated Sigmodon hispidus as the probable host of a hantavirus in Florida. Of 813 P. maniculatus tested in the southwestern United States 30.4% were infected; 12 of 90 (13.3 %) S. hispidus from Florida were infected. The S. hispidus-associated virus has not been isolated in cell culture and its etiologic role in human disease is unproven. The rodent reservoir for the third virus, associated with a fatal case of HPS in Louisiana, is unknown. These viruses are genetically distinct from their old world relatives, and cause a different spectrum of human disease. In the United States, respiratory disease is prominent while renal disease is most often reported from Eurasia. As yet the number of HPS cases occurring annually in the United States is unknown, but since the syndrome was identified in May, 1993, 50 cases have been reported from 15 states with an overall mortality ratio of 60%. The risk to groups occupationally exposed to rodents is being investigated.

Wild carnivores as plague indicators in California - a cooperative interagency disease surveillance program

A cooperative interagency program of sampling and testing wild carnivores for plague antibody has been utilized as an important component of an integrated plague surveillance program in California since 1974. The carnivore serology program involves the California Department of Health Services, the U.S. Department of Agriculture, APHIS/Animal Damage Control, the U.S. Department of Health and Human Services, Centers for Disease Control, and various other cooperators. This paper summarizes the results of the testing of wild carnivores, opossums, and feral pigs over the past two decades from 49 of California's 58 counties, and discusses the importance of the program to the overall statewide plague surveillance and control effort. A total of 8,962 samples have yielded 1,076 plague positives from wild carnivores, opossums, and feral pigs in 32 California counties. The highest percent positives have been from pine martens, mountain lions, bobcats, and grey foxes. A propensity for certain rodent prey species may increase the chance of plague infection for individual carnivorous species. The methodology has proven cost effective, allowed for detection of plague over a broader scale and in regions with no previous disease history, and demonstrated persistence of disease in apparent geographical foci within the state. In addition, the sampling of carnivorous animals in winter/spring in specific endemic regions has proven useful as an early alert system for disease activity, preceding summer plague epizootics among susceptible rodent populations, and when human plague cases associated with epizootics normally occur.

The role of predators in the ecology, epidemiology, and surveillance of plague in the United States

Predators play important roles in the ecology, epidemiology, and surveillance of plague in the United States. Most predators are accidental hosts of plague and, with the possible exception of grasshopper mice (Onychomys spp.), are not important sources of infection for feeding fleas. However, predators undoubtedly do play an important role in the natural cycle of plague by transporting infected fleas between different populations of plague-susceptible rodents. Predators are known to be at least accidental hosts for 40 of the 50 flea species that have been found to be naturally infected with plague in the U.S. Carnivores, including domestic cats, also play an important epidemiological role and have been sources of infection for 24 human plague cases since 1970. Serosurveillaoce of rodent-consuming carnivores is currently the most cost-effective method of monitoring plague in the western U.S. During the 1990s, these surveys have allowed CDC and other public health agencies to both identify plague risks for humans living in endemic regions and document the spread of plague into areas where it had not been identified previously.

The European ferret, Mustela putorius (Family Mustelidae): Its public health, wildlife and agricultural significance

The European ferret, Mustela putorius, a species prohibited in California, has become increasingly popular as a household "pet." As a result, its threat to public health, wildlife and agriculture has markedly increased. There has also been a consequent increase in reported attacks on humans, especially infants, including several fatalities. Reports of rabid European ferrets are also on the increase. When European ferrets establish "feral" populations, domestic poultry, waterfowl, game birds, rabbits and other species are at substantial risk. At this time, a California Legislature Assembly Bill has been introduced to change the status of the European ferret from a wild animal to a domestic pet. Passage of this bill would allow unlimited legal importation into California of this now prohibited and potentially detrimental species. The opportunity is therefore taken to increase the public's awareness on the dangers of European ferrets and by extension to also include other exotic wild animals as "pets."

Unwanted guests: Evicting bats from human dwellings

Bats are the second largest order of mammals in the world. Their 925 species are found on all continents except Antarctica. Bats are in serious decline world-wide from shrinking habitat, persecution and pesticides. Historically, bats were recognized for consuming insect pests, but only recently has the critical additional importance of bats in pollination and seed dispersal of semi-tropical and tropical plants been recognized. Bats use artificial structures in place of lost natural habitat, resulting in their destruction out of fear and ignorance. The health risk to humans from bats in buildings is extremely low, but where bat removal is necessary, non-lethal exclusion methods can be very effective.

Pindone for rabbit control: Efficacy, residues and cost

Toxins are a major component of rabbit control campaigns in New Zealand, with sodium monofluoroacetate (1080) being the primary toxin in use since the 1950s. However, landowners can use 1080 only under the direct supervision of a licensed operator, and rabbit populations in regularly-poisoned areas have become increasingly resistant to this form of control. A new, cost-effective toxin that does not cause persistent residues in livestock is required by landowners who wish to undertake their own rabbit control. Several recent trials have demonstrated the potential of the anticoagulant pindone (2-pivalyl-1,3-indandione) to meet these requirements. In 1992, the New Zealand Pesticides Board granted full registration to cereal pindone pellets, so that for the first time the New Zealand public has access to a rabbit bait that does not require a licence for its use. The bait is being used with apparent success in a wide range of situations, with sales of the product exceeding 100 ton in 1993.

Preventing deer damage with barrier, electrical, and behavioral fencing systems

White-tailed deer (Odocoileus virginianus) are responsible for damage to a variety of horticultural crops. Economic losses often require growers to implement one or more damage management methods including repellents, scare devices, hunting to control deer numbers, and fencing. A relatively small proportion of producers currently use fencing as their primary deer damage management technique due to high initial costs and other perceived shortcomings. Several fencing systems, including baited single wires, three-dimensional outriggers, and slanted and vertical fences up to 3.3 m (11 feet) in height have successfully excluded deer under some conditions, but simple designs are effective only under light deer pressure, or for relatively small (< 5 ha) areas. Low-cost fences are seldom satisfactory for protecting commercial orchards or ornamental plantings during winter, especially if snow restricts normal deer foraging opportunities. Combining electric fences with either attractants or repellents can enhance their effectiveness. Recent experiments with invisible electronic fencing systems and dogs have resulted in reduced deer damage to crops, however, additional research is needed to determine dog density per unit area for reliable protection during winter. Actual costs for fence installation vary depending on site characteristics, labor quality and costs, and sources of materials. It is important for growers to calculate the annual fencing costs for an orchard or nursery based on the anticipated life-expectancy of the fence design.

Potential repellents to reduce damage by herbivores

Economic losses caused by herbivores and other species that inflict damage by browsing or gnawing are substantial. Because lethal approaches to damage reduction are not always practical or desirable, there is an increase in interest in the development of alternative, non-lethal technologies. Repellents may provide a feasible alternative. Here, we present recent studies of three repellent types: 1) anthranilate derivatives (e.g., methyl anthranilate), 2) predator scents (e.g., coyote urine), and 3) bittering agents (e.g., denatonium saccharide). Anthranilate derivatives and predator odors both appear to be promising repellents. Avoidance of the former substances is based on irritant volatiles, and anthranilates may be especially beneficial when the aim is to prevent gnawing damage. Predator odors may be most applicable for protection of vegetation. The effectiveness of these substances appear to be based on the presence of highly volatile, light molecular weight sulfur compounds. Unlike anthranilates or predator odors, bitter substances are largely ineffective as repellents for herbivores.

How birds interpret distress calls: implications for applied uses of distress call playbacks

Distress call playbacks are used as deterrents to keep birds out of areas where they are causing problems. However, the calls often are ineffective, owing to birds' rapid habitation to them. Recent studies on the functional significance of distress calls indicate that adult passerines only distress call when physically constrained and that the calls are designed to startle the predator holding the caller into releasing it. Further, distress calls attract other birds, which approach the caller to acquire information about the predator. These findings suggest that distress calls would be more effective if their broadcast is paired with a predator model that appears to be grasping the caller. Such a pairing should reinforce a bird's fear of the predator model and delay its habituation to the distress call.

An overview of avian predation and management techniques at fish-rearing facilities

As the aquaculture industry continues to expand in the United States, so too do the losses attributed to wildlife depredation. Because the industry is so diverse and the various types of culture are characterized by unique designs, operations, and arrays of cultured species, there is a need for corresponding uniqueness in predator management strategies and techniques. It is unlikely that, at any time in the near future, one universal method or approach will be developed to successfully resolve wildlife depredation problems in all facilities. However, numerous areas for improvement currently exist where potential reductions in the extent of loss can be achieved with minimal impact on the industry. Additionally, the industry must be willing to accept some loss simply as one of the natural costs of doing business.

Grower practices for blackbird control in wild rice in California

We surveyed 29 wild rice growers, representing 96% of the California acreage grown in 1993, to determine current practices for blackbird damage control. Twenty-seven growers (93%) had blackbird damage. The period of greatest damage and most intensive control was July through September. Red-winged blackbirds (Agelaius phoeniceus) most frequently caused damage, but three other species of blackbirds and the European starling (Sturnus vulgaris) were also identified. Most growers (72%) reported 1 to 10% yield loss. Average loss ranged from $121 to $309/ha, and from $14,530 to $32,061/grower. Most growers (97%) attempted to control blackbirds for an average of 3.5 months during the growing season, relying primarily on shotguns, propane cannons, shellcrackers or bird bombs, and patrols. Growers in northeastern California tended to rate these techniques as more effective than growers in the Sacramento Valley, possibly due to the larger field sizes in the Valley. Average effectiveness ratings for all techniques indicated little better than slight control for the techniques used, suggesting grower dissatisfaction with the available techniques. Average cost for control averaged $86.21/ha, which was among the highest costs for any single aspect of wild rice production.

Field tests of a copper-based fungicide as a bird repellent rice seed treatment

In east Texas, bird damage to sprouting rice was reduced in two of seven study plots when rice seed was treated with the fungicide Kocide® SD at the maximum label rate (8 fluid oz/100 lb seed). Foraging rates of male redwinged blackbirds (Agelaius phoeniceus) in treated plots were lower P = 0.02) than were those in control plots. We suspect that the copper in Kocide SD produces physiological effects that suppress feeding activity that results in reduced losses in some cases. Because it is registered for use on rice and is relatively inexpensive, Kocide SD may be a useful component of some bird damage reduction strategies.

Alpha-chloralose: Current status, restrictions and future uses for capturing birds

In 1992, the Animal Damage Control (ADC) program received approval from the Food and Drug Administration (FDA) to use Alpha-Chloralose (A-C) nationwide for capturing waterfowl (Anatidae), coots (Fulica americana), and pigeons (Columba livia). To review the first year (1993) of operational use of A-C, we surveyed in January 1994 all ADC State Directors on the status of A-C use within their states. In 1993, 59 ADC personnel were trained and certified in the approved uses of A-C and 696 nuisance waterfowl were captured with A-C in 10 states. Restrictions imposed by U.S. Fish and Wildlife Service (FWS) and state permits regarding "incidental take," relocation, and euthanasia were responsible for the minimal use of A-C in 1993. Meetings were held in September 1993 and January 1994 to address: 1) the problems with FWS permits; 2) plans for future approved uses of A-C for additional species; 3) the availability of A-C to personnel and agencies outside the ADC program; and 4) provisions for nonapproved uses of A-C (special, emergency and non-emergency situations).

Bird control in New Zealand using alpha-chloralose and DRC1339

Horticulturists and the general public in New Zealand are experiencing increasing problems with a number of introduced bird species. This has meant that many people wish to carry out bird control operations themselves to reduce the problems these birds cause. Most of this control will have to be carried out by the growers themselves as there are very few professional bird control personnel in New Zealand. Alpha-chloralose is the only toxin the general public has access to for controlling birds. It is available in a variety of bait forms with a maximum toxic loading of 2% (weight/weight). Registered personnel can use alpha-chloralose and DRC 1339 (Starlicide) to control birds, although at this stage DRC 1339 is only available for rook control. A wide variety of unusual baits have been used to control rooks with this poison.

Laboratory studies with compound DRC-1339 on feral pigeons

Laboratory studies were conducted to determine an effective DRC-1339 concentration and bait dilution ratio to control pigeons. Treated whole corn baits formulated with Alcolec-s®, corn starch, or corn oil as adhesive agents and 0.25% or 0.37% DRC-1339 diluted 1:5 with untreated corn produced < 10% mortality. DRC-1339 treated whole corn baits (0.25% and 0.37%) diluted 1:0 and formulated with Alcolec-s® produced 20% and 5% mortality, respectively. Whole corn treated with 0.37% DRC-1339, diluted 1:0, and formulated with corn starch produced 68% mortality in laboratory-held pigeons and was selected for further evaluations in field studies to provide efficacy data to the EPA. DRC-1339 residue levels observed in pigeons free-feeding on 0.37% undiluted DRC-1339 treated corn was not detected in breast tissue and only occurred in the gastrointestinal tract of two of five pigeons at 0.06 and 0.19 ppm. DRC-1339 residues observed in pigeons force-fed 21 whole corn kernels treated with 0.37% DRC-1339 (approximately 5 times the LD50 dose) were not detectable after 3 h in breast tissue and 24 h in the gastrointestinal tract. DRC-1339 residues in pigeons gavaged with 58 mg DRC-1339 (over 10 times the LD50 dose) were detectable in the breast muscle of four of nine pigeons at 0.061 to 0.10 ppm. DRC-1339 residues in the gastrointestinal tract ranged from 0.13 to > 17 ppm in eight of nine treated pigeons and was not detectable in the remaining pigeon.

ReJeX-iT™ AG-36 as bird aversion agent for turf and agriculture

In limited field studies on turf, winter rye, cherries and blueberries, where the presence of sufficient concentrations of ReJeX-iT™ AG-36 were known to exist, excellent bird repellency was achieved. Variations in the results are attributed to low concentrations of the initial application, rapid biodegradation due to environmental conditions, or limited application (covering less than 100% of the test plot).

Red-winged blackbird feeding preferences and response to wild rice treated with Portland cement or plaster

The California wild rice (Zizania aquatica) industry considers red-winged blackbirds (Agelaius phoeniceus) their most important pest problem. Farmers often have asked if crop-damaging blackbirds can be killed by mixing dry Portland cement or plaster-of-Paris with grain bait. We conducted a series of tests to determine the effect of cement or plaster mixed with wild rice fed to captive redwings and to determine feeding preferences of redwings for wild rice in relation to other grains. Birds would not eat cement- or plaster-treated rice when untreated rice was available and no mortality occurred when birds were offered only treated rice over a four-day period. Thus, treating grain with cement or plaster will not kill redwings but cement or plaster might serve as useful bird repellents for seed grain. Proso millet was strongly preferred over wild rice by redwings, indicating millet would be an excellent candidate as a lure crop and as a bait for trapping or for delivering a chemical. Sunflower would perhaps not be a preferred bait or lure crop in wild rice areas and cracked corn would not be a preferred bait.

Developing an electrified fence to exclude rabbits from crops

The effectiveness of a new design of electric strained wire fence (CSL fence) for managing rabbits is currently being assessed in a two year trial. It is being compared with a commercially available electric netting fence (Flexinet fence) and also with farmers' normal control methods. The study is taking place on commercial farms in Cornwall, England, where the fences are being erected to protect fields of cauliflower. The amount of rabbit damage to individual plants in each field is being assessed and the numbers of rabbits feeding in these fields are being counted. Plant yields at harvest will also be used to determine effectiveness. Observations of rabbit behavior at the CSL fence are being conducted to identify potential design problems and to assess solutions to these problems. There was no difference between the effectiveness of the two fences during the first six months of the trial. Few plants were completely eaten by rabbits in the protected fields (CSL fence: 5±6%; Flexinet fence: 0%) but, by contrast, most were eaten at the control sites (82±17%). No more than a single rabbit was ever counted at night on the CSL- (0.7.±0.1 rabbits) or Flexinet- (0.5±0.2) protected sites but up to 20 (17.0±3.0) were counted on the control sites. The few rabbits which were observed crossing the CSL fence either jumped through or over it. The CSL fence design is proving to be extremely cost-effective and in this trial it would already have recouped its costs many times over if it had been used to protect the control fields. It will be further tested next year. The research was funded by the Horticultural Development Council.

Improving aerial control of possums by precision bait delivery

Aerial delivery of 1080 (sodium monofluoroacetate) baits is the main technique for reducing populations of New Zealand's foremost vertebrate pest, the Australian brushtail possum, in large areas of inaccesible country. Surveys after pilot-controlled aerial sowing of baits in seven operations in forests showed that inaccurate navigation along the swaths left up to half the target zone untreated. Kill was estimated to average 75%. Inadequate coverage with baits was therefore believed to be a major factor in the survival of possums during aerial control operations. This was confirmed in field trials using rhodamine B as a biomarker to reveal acceptance of non-toxic baits. More possums were unmarked in partially treated blocks than in completely treated blocks. After a large-scale aerial control operation, proportionally more possums survived in untreated gaps than in treated areas. Six operations that used navigation guidance systems (Decca Flying Flagman and GPS) yielded complete coverage and high levels of kill (mean of 92%) in five. Precision sowing of possum baits prevents survival of possums by failure to encounter baits, and enables lower rates of bait application. This will give large cost savings and improved environmental safety. A small proportion of a population may still not be targeted because of individual dislike of bait or failure to encounter baits because animals stayed in the forest canopy during operations. Development of more palatable and longer lived baits may facilitate local extermination of possums.

Biological management (control) of vertebrate pests - advances in the last quarter century

In 1967, Howard provided a review of biological control of vertebrate pests. The term "biological control" was borrowed from the field of entomology, where it has been traditionally defined as "the reduction in number or density of pests through biological processes such as predation, pathogens, habitat modification, and fertility control." Current philosophy in wildlife damage management advocates "the reduction of damage to a tolerable level" rather than "the reduction of the number or density of vertebrate pests." Therefore we abdicate the term "biological control" and encourage the use of a new term, "biological management" of wildlife damage. Advances in science in the past 25 years have led to the testing and potential development of several biological methods for controlling wildlife damage and nuisance problems. We provide a nonexhaustive review of research in the following areas: secondary plant defense compounds, morphological plant defenses, predator odors, predation aversion compounds, pheromones, habitat modification, introduced and endemic predators, micro- and macroparasites, and fertility control through chemosterilants, genetic manipulation, and immunocontraception. No methods have been fully developed or are without problems. Several constraints associated with the development of biological management strategies are discussed.

The prospects and associated challenges for the biological control of rodents

Biological control using macro- or micro-parasites is a promising research area for control of rodents. The largest impediment to progress is a dearth of high quality research, under field conditions, on wild rodents and their diseases. A major challenge is to identify a candidate control agent which is sufficiently pathogenic, has a high transmission rate and is target specific. Once this has been done, ecological studies of both the host and the disease agent, and of the epidemiology of transmission, are required. Whether the desired pathogenicity is via increased mortality and/or reduced fertility will depend on the agent and on the dynamics of the pest species in particular agricultural systems. Overall, the best prospects for the biological control of rodents lies with agents that reduce fertility rather than increase mortality. The development of immuno-contraception using a virus as a vector is proffered as the most promising generic approach for the biological control of rodent pests.

Developing international trap standards - a progress report

ISO, the International Organization for Standardization, formed a technical committee in 1987 to develop an international standard for humane traps. This effort began with the establishment of international Working Groups charged with preparing standards for killing and restraining traps. Capture efficiency, humaneness, injury thresholds, selectivity, testing, and safety are addressed in the standards. A final draft standard could be voted on by ISO member countries by mid-1995.

Policy considerations for contraception in wildlife management

Managing wildlife populations by manipulating their birth rates is a promising technology. However, the use of contraceptive technologies will involve the development of new wildlife management policies. We designed and implemented a survey that was intended to gather information on the range of perspectives of concerned publics on contraceptive use in wildlife management. There appears to be considerable confusion and mistrust regarding the application and appropriateness of this new technology. We recommend that promoters of contraception use in wildlife management be careful to explain what this new technology can and cannot do in order to avoid the pitfalls associated with trying to deliver false promises.

Managing raccoons, skunks, and opossums in urban settings

Increased urbanization and decreased government funding, plus increased numbers of certain wildlife species, have combined to provide a greater need for wildlife management of nuisance animals in the urban environment.  The author cites data from a 1989 National Pest Control Association survey of private wildlife pest control services, which notes that the most common species complaints deal with mice and rats, squirrels, birds, and bats, followed by raccoons, skunks, moles, and others.  The biology of, damage caused by, and effective damage control methods for tree squirrels, raccoons, skunks, and opossums are discussed.

What do animal activists want? (and how should wildlife managers respond?)

National animal activist organization leaders were interviewed with the aim of better understanding their ideologies with respect to wildlife issues. Interviewees expressed considerable concern about traditional wildlife management practices and associated consumptive recreation activities. They easily identified a number of needed changes, while had difficulty identifying things they liked about the status quo. The top suggested changes related to using more nonlethal management methods and reducing allegiance with consumptive users. The most common "bottom line" concern expressed by interviewees was the alleviation or elimination of unnecessary pain and suffering in wildlife.

Using Geographic Information Systems for tracking an urban rodent control program

Geographic information system technology is being used to help coordinate an urban rodent control program initiated as part of the Central Artery/Tunnel Project in Boston. Databases with neighborhood survey data, surface and subsurface baiting data, sanitation code violations, and public complaints are linked to base mapping, land parcel, and utility graphics. This integrated approach helps Project biologists plan control strategies and evaluate the relatedness of rodent activity to environmental conditions. Spatial querying techniques and the ability to graphically display and map variables, such as bait stations and sanitation deficiencies, help ensure that control resources are effectively targeted and tracked. This technology application and the design principles involved provide a model for managing urban rodent control programs.

Evaluation of field sampling techniques for estimation of bird damage in pistachio orchards

Pistachio orchards were selected and evaluated for damage caused by either scrub jays (Aphelocoma coerulescens) or American crows (Corvus brachyrhynchos). The distribution of damage caused by each species was evaluated and quantified. The percentage of trees damaged by scrub jays ranged from 58% to 99% and tended to be distributed randomly throughout the orchard. In orchards with crow damage, the percentage of trees damaged ranged from 18% to 46% and damage tended to be aggregated. Data from orchards were used to evaluate the relative accuracy and precision of various sampling strategies. Randomly distributed bird damage could be sampled with relatively simple strategies such as walking diagonally across the orchard. Aggregated bird damage was most effectively sampled using stratified random sampling. If action thresholds are going to be used to determine when bird control programs should be initiated, an understanding of the distribution of bird damage in a crop must be understood so reasonable sampling techniques can be developed.

Sources of information on wildlife damage control

People encounter a great diversity of damage problems caused by wildlife, for which they need effective and timely solutions. Published materials or sources of help often are scattered, difficult to locate, and often members of the public struggle to find help in dealing with problem wildlife. The author describes three fictional scenarios, based on his experience in helping people find reputable information on solutions to wildlife damage problems. The article lists federal, state, and local agencies within California that can provide assistance and information concerning vertebrate pests; lists recent publications that are helpful sources of information; and lists organizations and professional associations that facilitate knowledge and training regarding wildlife damage management.