Proceedings of the Vertebrate Pest Conference

Lack of adequate information is emphasized as a major problem in attaining effective control of damage by vertebrate pests, and it is stressed that the problem is widespread in all elements of the public, including those directly involved, like producers and government officials, as well as those only indirectly involved, like the average citizen. A number of specific examples are cited to illustrate the problems of uninformed or inadequately informed publics.

4-aminopyridine, a chemical frightening agent, has proved effective for protecting field corn, sweet corn, sunflowers, peanuts, and pecans from attack by birds, chiefly blackbirds. Problems in more effective use of the product, Avitrol FC Corn Chops 99, by growers include restricted availability; a restricted number of certified applicators, few of whom have the time to attain an adequate knowledge of bird damage problems and to put forth a concerted and maintained baiting effort that is necessary to obtain the best results; a weakness in use directions that causes much of the bait to be squandered or used less effectively; and application and bait costs that have risen faster than the value of crops, primarily because restrictions on product use have resulted in treatment of only a small fraction of the acreage that could be profitably baited. Improvement in use directions for the product, making it available to the grower through more direct channels, and training individuals to lead effective baiting programs are the solutions suggested.

The cattle feedlot affords an ideal habitat for large concentrations of birds. Several species are primarily involved in feed depredations and contamination. The development of an integrated systems approach to control involves the interaction of human attitude, cultural control practices and application of bird damage control techniques, each of which is a dynamic system in itself.

Seed rice was treated with 0.25% methiocarb to test its effectiveness as a blackbird repellent in Vermilion Parish, Louisiana in the spring of 1975. Two replications of 3 treated and 3 untreated plots showed 68% more seedlings in treated plots (2,393) than in untreated plots (1,429). Half as many birds (chiefly redwing blackbirds, Agelaius phoeniceus, were recorded in treated (1.18/min) as in untreated plots (2.39/min).

An in depth look at the principal requirements of an orderly and systematic approach to vertebrate pest problems in Canada is presented (Part I) as a prerequisite to a proposed theoretical model illustrating the involvement of various agencies. A model depicting how these agencies could best utilize their available resources towards the development of improved vertebrate pest control technology is presented in Part II. The involvement of private consultants in vertebrate pestology is relatively new (and perhaps unappreciated), yet offers substantial potential in the development of selected facets of the vertebrate pest field. The proposed roles of other agencies are discussed with respect to advantages of improved co-ordination of effort, and the increased utilization of private consultants. Congruent with revised National Science Policies, predictions are offered regarding the importance of future expansion of industrial involvement (manufacturers, private consultants, private testing and research laboratories and others) in research and development of vertebrate pest control. Although the program requirements and proposed administrative model for a vertebrate pest control program pertain to the situation in Canada, the general principles lend themselves to application elsewhere.

Attempts to reduce blackbird numbers by spraying roosts have created considerable controversy. Opinions and suppositions fuel this controversy; yet, until now, decision makers have had no quantitative tools to predict the impacts of population reduction or to aid in formulating management strategies. To improve the predictive ability, we have synthesized data on red-winged blackbird (Agelaius phoeniceus) populations into a computerized system, BIROS (Blackbird Information Retrieval and Data System). Grackles (Quiscalus quiscula), cowbirds (Molothrus ater), and starlings (Sturnus vulgaris) will be added to the system later. BIROS is designed to estimate the number of redwings for any area of North America at the start of the nesting season, to simulate the annual cycle of numbers for the population, and to trace the general movements of the population. BIROS, when complete, will give us the ability to estimate the immediate numerical effect on a population for any management operation involving lethal control. Two examples of hypothetical management strategies demonstrate the output generated by BIRDS and how this information can be used in making management decisions.

Studies by the U. S. Fish and Wildlife Service of the efficacy of methiocarb for reducing bird damage to sprouting corn, rice, soybeans, lettuce, and sugar beets, and to ripening rice, grain sorghum, wheat, cherries, grapes, and blueberries have shown it to be an effective, broad-spectrum bird repellent and crop protectant. The short-term plans of the Service for the further development and testing of methiocarb are reviewed. Also discussed is some of the rationale behind the use of chemical repellents to prevent agricultural damage by birds.

Breeding populations of nuisance bird species were related to various types, designs, and quality of building construction in Columbia, Maryland. Since there were differences in the various parts of this new, planned city in types, builders, and architectural designs, it affords an excellent opportunity to study the effect these factors have on bird populations. Breeding starlings (Sturnus vulgaris), house sparrows (Passer domesticus), and pigeons (Columba livia) were unevenly distributed throughout the city, being concentrated in those specific areas with buildings having design or quality features that were favorable to these species. Specific examples of building designs and/or flaws in construction that created nuisance bird problems are described. Nuisance bird problems in newly constructed urban areas can be avoided by not using building designs that favor these birds and by preventing construction flaws that afford nuisance bird habitat.

The manner in which an experiment is conducted determines the inferences that can be made from the results of the analysis of the experiment. This paper emphasizes the critical need in pest-damage control (PDC) experiments for a detailed planning process (i.e., the design of experiments) by exampling improper designs that prohibit a researcher from making valid inferences about his hypotheses of interest. Emphasis is placed on identification of experimental units, determination of restrictions on the randomization procedure, and specification of treatment forms of pest control materials. A list of some specific actions to strengthen PDC experiments is given.

Vineyard losses to birds are primarily due to two species; these are the starling (Sturnus vulgaris) and the house finch (Carpodacus mexicanus). The majority of losses in the Central California Coastal region are caused by the starling, due to the large numbers of migratory birds arriving prior to harvest. Starlings are best controlled by a combination of pyrotechnic and acoustic devices. Linnets are most effectively controlled by trapping and poisoning. No matter what type of control is used, it is necessary to have sound knowledge of the birds' behavior and reliable personnel carrying out the program. An effectively run program can reduce losses by as much as ninety percent.

A brief history of the development of the winegrape industry in Monterey County, California is provided. In the early 1960s, several established wineries pioneered the initial premium varietal vineyards in the county, with very successful results. The early 1970s brought a grape planting boom: acreage jumped from 2,000 to over 37,000 acres in approximately 4 years. While a few of the early vineyards had suffered damage from starlings and linnets, the increased acreage brought increasingly significant bird damage problems. It was recognized that a county-wide bird damage control program needed to be developed, but there was little information on current effective methods, damage assessment, or costs of control methods. The county Agricultural Department assisted by instituting grower assessments to provide funds to hire local personnel, who would coordinate our efforts to apply and evaluate damage control methods. Currently, we have what we believe is the beginning of an effective program that utilizes bird traps, bait trays, and sound-scaring technologies. The program provides important communication among growers, in addition to timely sharing and implementation of tools and techniques. We believe that academic institutions need to be more directly involved with the growing animal damage problem at a field level, and to recognize the inadequacy of current research efforts.

Difenacoum is a new rodenticide recently introduced on the British market; it is one of the most potent of a series of hydroxycoumarin-based anticoagulants. Difenacoum is effective against laboratory rats and mice resistant to conventional anticoagulants and has a marked selectivity in favour of non-target species. Vitamin K1 is an effective antidote and the hazard of secondary poisoning is minimal. Laboratory and field trials confirm difenacoum's efficacy against wild resistant strains. Further work is in progress to evaluate the efficacy of difenacoum against other rodent pest species.

Strychnine alkaloid baits were consumed by both captive and wild beaver without any apparent hesitation. An approximate minimal acute lethal dose of sodium monofluoroacetate to beaver of mixed ages and sex was 0 .202 mg/kg. Trapping beaver on four study area watersheds in Alabama with No. 330 conibear traps for approximately two weeks in winter during two successive years essentially eliminated beaver. Older individuals were trapped the first year, maturing juveniles and the remaining few adults were trapped the second year, and there was very little reproduction between the trapping periods. Trapping, with its recreational appeal, and income and food potential seems the better and more prudent approach to control of nuisance beaver than others being considered.

Attempts to reduce populations of Spermophilus beldingi oregonus have centered around the application of Compound 1080 and strychnine baits. Additional population reduction techniques were investigated for possible employment into the squirrel program. Techniques which show much promise are: hand baited chopped green bait (.01% chlorophacinone), broadcast (10 pounds per acre) and hand baited grain bait with .01% chlorophacinone and .05% fumarin, and bait stations using .01%, .05% chlorophacinone grain bait (100 and 200 foot spacing) and .05% fumarin grain bait (100 foot spacing). In addition, the concentration of Compound 1080 on chopped green bait can be reduced to 1/4 oz. of 1080 per 250 pounds of chopped green bait broadcast at 10 pounds per acre. Preliminary investigation in damage assessment using exclusion cylinders resulted in 123 squirrels per acre removing an average of 1,790 pounds (spring growth alfalfa - downy broom) per acre in 44 days. Stomach content weights were determined over a 3½-month period. Feeding behavior and average daily food consumption is greater early in the year (May) than later (July).

By County Ordinance the County Agricultural Commissioner has been charged with rodent suppression in Fresno County, California. For nine years personnel from the Agricultural Commissioner's Office have conducted a county operated and funded program of ground squirrel suppression through the use of aerially applied zinc phosphide-treated squirrel oat groats. Planning procedures, relative costs, and operational aspects of the program are outlined. This technique of ground squirrel suppression has been shown to have many advantages over hand application of rodent baits. No known hazards to non-target wildlife species have been demonstrated.

Vertebrate pest problems are foremost economic, political and social rather than biological anomalies. Students are often turned away from vertebrate control, which is applied ecology, by professors who know only theory and do not understand the ecology of man-modified environments. Applied ecologists seeking alternative methods of vertebrate control benefit environment far more than the negative, anti-control approach based on half-truths that are used for self-serving purposes by many protectionist organizations and government leaders in CEQ, EPA and USDI. A healthy ethic, with deep ecological conscience, would be to appreciate the glory of death in nature, for death means life to other individuals within a species. A vertebrate control operation has benefit factors other than the individual or species being controlled, whereas the objective of wildlife management favors the well-being of local populations of the species in question. Since Land-Grant Universities are geared for research and extension support from the USDA, it is a mistake to have the responsibility for vertebrate pest control in the conservation wildlife-management oriented Fish and Wildlife Service of USDI.

Current rodent control practices for the Hawaiian sugar industry revolve around the use of single grain baits containing anticoagulants in bait stations and zinc phosphide for aerial applications. Neither type of control programs as they are now applied has been very effective against the Norway rat (Rattus norvegicus) which is becoming a major problem species for the industry. As a result, we have sought a more effective anticoagulant, to which the Norway rat is more susceptible, and an improved method of bait distribution. With a knowledge of the month-to-month variation in the field rodents' gestation rate, a new control program is being developed which involves the distribution of diphacinone oats in plastic bags to precede the major annual gestation peaks.

Common methods for mole control are baiting with earthworms impregnated with thallium sulphate or strychnine, gassing with pellets developing phosphine, and trapping. Seasonal cycles in burrowing activity make it difficult to evaluate results of expensive control campaigns and may give a false impression of efficiency.

Pocket gophers (Thomomys talpoides) in environmental systems adapted readily to laboratory conditions. The laboratory equipment is described in this paper. Results are reported, including data on food consumption as it varies with the activity patterns of the gopher and the variation between individual gophers. One gopher used an average of 52 g of food per day for a 131-day period, but during an extremely active 17-day period, the gopher consumed approximately its own weight in food each day (75 g). The experimental setup is described for food location experiments and results indicate that gophers locate their food primarily by odor. Test animals react very quickly (in seconds or minutes) to odor stimuli if the gopher's food cache is depleted and the animal is hungry.

The California Department of Food & Agriculture, under an experimental permit, tested sodium cyanide spring-loaded ejector mechanisms for coyote control in Tehama County. These devices were compared to other traditional methods of coyote control to protect sheep from predation. The effectiveness of the devices, as well as their economy of use, could not be determined, as moisture leakage into defective sodium cyanide capsules limited their utility. IT was projected that cost per coyote taken using the devices would have been $68 per coyote, which was a substantial savings as compared to other coyote control methods. The study indicated that coyote control operations can be conducted using the devices without unreasonable adverse effects on the environment. No accidents with the devices occurred during their use by trained staff during the 8-month study. While aerial hunting and ground shooting achieve the most selective means of taking coyotes, the sodium cyanide ejector devices were more selective in taking coyotes than were steel traps. However, the use of steel traps on nontarget wildlife populations was negligible.

The justification and economics of the operational animal damage control program in California as conducted by the U. S. Fish and Wildlife Service are discussed. Emphasis is given to the necessity for use of the steel trap. Nearly 83 percent of the depredators are taken by trapping. Annual agricultural losses due to predation were estimated at $4.7 million in California for Fiscal Year 1975. The projected cost-benefit ratio was 1:3.9.

Private aerial hunting of predators for protection of livestock began before 1925 in the western United States. Apparently, it was first used in professional control programs in 1942. Inclement weather, dense vegetation, and rough terrain are limiting factors and helicopters are more versatile than fixed-wing aircraft. When it can be employed, aerial hunting is unsurpassed as an immediate control method where livestock losses are severe and the need for control is urgent.

Sodium cyanide was cancelled for use in predator control in March 1972 along with strychnine and 1080 mainly because of the indiscriminate use of these poisons which posed an imminent hazard and danger to the environment. After due consideration, the EPA Administrator in January 1974 authorized approval of experimental use permits (under Section 5 of FIFRA as amended) for use of sodium cyanide in the M-44 device (SCSLEM) in order to accumulate information necessary to support registration consideration. Subsequently nine permits were issued for this purpose. In August 1975, a public hearing was held in Washington, D. C. to respond to a formal application for registration by the Department of the Interior (U.S. Fish and Wildlife Service), since, in the judgement of the Agency, there was substantial new evidence to refute three main issues set forth in the March 1972 cancellation order. Following this hearing, EPA Administrator Train published his decision on September 16, 1975 which specified that sodium cyanide capsules for use in the M-44 device may be registered under Section 3 of FIFRA to federal and state agencies and to other persons provided that they sell sodium cyanide capsules only to state and federal registrants. Only state and federal registrants are permitted to sell, give or distribute sodium cyanide capsules to trained and supervised applicators. A total of twenty-six restrictions are included in this Order. To date EPA has issued 8 registrations for sodium cyanide capsules for use in the M-44 device.

A review of the literature reveals that over 60 chemicals have been used for the capture of wild animals, but only 30 of the most widely used chemicals are discussed in the present paper. For practical considerations these chemicals can be classified as being either (1) neuromuscular blocking agents, or (2) central nervous system (CNS) depressants. Some common neuromuscular blocking agents are d-tubocurarine, gallamine, succinylcholine, and nicotine. M99 and its derivatives, phencyclidine, and xylazine are some of the more commonly used CNS depressants. Neuromuscular blocking agents have a relatively rapid onset and short duration of action but they do not possess sedative, analgesic, or anesthetic properties. CNS depressants do produce desirable sedative, analgesic, and anesthetic effects, and frequently a combination of CNS depressants results in more desirable immobilization characteristics.

The paper reviews social interactions in small rodents in which pheromones have been reported to play a part. Some of the chemical messengers involved may have a potential use in control of rodent pests. Research in this field should be encouraged, because alternatives to the current control methods are highly desirable.

During application by airplane, excessive amounts of zinc phosphide were lost from the bait registered to control rat damage in Hawaiian sugarcane. The losses created unnecessary hazards and potentially reduced the efficacy of the control program. In a series of screening tests, alternate adhesives, adhesive concentrations, and bait mixing procedures were evaluated for zinc phosphide retention, acceptance by rats, phosphine residues in sugarcane and operational effectiveness. A formulation was developed that reduced zinc phosphide losses 92% during application, increased acceptance by rats, left residues in sugarcane below the established tolerance, and equaled or exceeded the performance of the original formulation.

Damage to coniferous seedlings and trees by forest rodents, including forest lagomorphs, is a major factor limiting prompt regeneration and causing significant losses in young stands. Manipulating the vegetation to adversely influence food and cover thereby reducing animal numbers is proposed as an approach to alleviating damage. The adaptability, high reproductive potential, opportunistic feeding behavior, and mobility of forest rodents combined with the species diversity of rodent communities, rapid recovery of vegetation, and need for long-term protection make habitat manipulation for damage control a difficult approach. However, an example is presented where herbicide-induced reduction in vegetative cover and availability of summer foods resulted in a significant reduction of clipping damage to Douglas-fir seedlings by snowshoe hares.

World food shortages become more acute each year, and all too often, rodents are present to take their unwarranted share. To counter this, we must refine our rodent control methods to make them more efficient. To this end, correct bait selection is essential. Grain baits must be selected for purity and acceptability. Grain alterations must be carefully controlled, as well as any additives. Multi-ingredient or composition baits must be checked for size, hardness, protein content, and additives. The selection of trap baits is critical for the success of trapping program. In general, fresh coconut is the best bait, but on-site local baits must be checked.

California State legislation as passed in 1971 established the Agricultural Pest Control Advisors licensing program with the intent of providing agriculture with competent and professional personnel who make pest control recommendations. Today, nearly 4,000 advisors are licensed in California and approximately 1,350 are licensed vertebrate pest control advisors. Recent amendments to the Federal Insecticide, Fungicide and Rodenticide Act will add new responsibilities to the advisor by requiring certification of both private and commercial applicators throughout the U.S. beginning in 1977. More than one-half of the vertebrate pest control advisors are employed in agrichemical sales while the remainder are employed by government agencies or are self-employed as consultants. Today, about one-third of the licensed vertebrate pest control advisors are not actively using the license and of the remaining licensed two-thirds, 94% are infrequently engaged in making vertebrate pest control recommendations. Control recommendations are most often made for rodent and bird pest problems. The majority of advisors feel that additional training, education, and upgrading of the industry is important for all advisors.

Concern over pocket gopher damage to conifer seedlings is increasing rapidly in the northwestern United States. The evolution of the pocket gopher (Thomomys spp.) has resulted in an animal that occurs throughout northwest forested areas and responds to site disturbances by increasing numbers and distribution. Pocket gophers kill or slow growth of conifer seedlings. More extensive logging, wildfires, and insect epidemics are resulting in more damage problem areas. This will continue. Current damage control is judged poor. Juvenile dispersal, high natural mortality rate, need for intensive treatment on entire damaged areas, current dependency on pesticides for control, increasing wood product values, and decreasing tolerance for reforestation delays are causing this increased concern. Integrated control appears necessary for the future.

Birds and rodents eat pine seeds needed for regeneration, and the larger mammals destroy established seedlings by browsing or trampling. Some of the problems they cause have been solved or solutions are near; some still defy solution.

A federally funded rat control project is being conducted by the Vector Control Section, California State Department of Health in cooperation with local health agencies in the San Francisco Bay Area. Four community demonstration areas were selected in urban poverty areas in the region. The objective of each demonstration program is to reduce the rat infestation to a level that will not have significant adverse health or economic effect. Environmental improvement and community participation are emphasized. Concurrent studies are being conducted to determine the status of anticoagulant resistance, the occurrence of rodent-borne diseases, and the significance of rat infestations in sewer systems. The information gained from the project will provide improved methods and management criteria for rat control programs in the San Francisco Bay Area and other areas of the State with similar rodent problems.

The use of cultivation three times a year (May, July, and November) or cultivation plus a residual herbicide twice a year (July and November) greatly aided in the control of pine voles Microtus pinetorum (LeConte) in apple orchards. The use of Chlorophacinone (CPN) or Diphacinone (DPN) baits placed by hand in holes and runs 2-3 weeks after the November cultivation resulted in a very effective control procedure. Without cultivation at least two applications of anticoagulant baits at the rate of 10 lbs/acre each were required to insure adequate control. Due to low apple prices in 1975, large numbers of dropped apples existed under trees when apple and prepared hand baits were applied. We believe dropped apples interfered with control achieved with toxic baits.

Studies in Mexico in 1972 showed that diphacinone (Diphenadione) (2-diphenylacetyl-1,3-indandione) was effective in reducing both vampire bat (Desmodus rotundus) populations and the incidence of bat-transmitted rabies in cattle. Two highly selective methods were developed: treating cattle systemically and treating vampire bats topically. Since 1972, Denver Wildlife Research Center personnel have assisted Latin American Ministries of Agriculture in developing control campaigns. Brazil, Bolivia, Colombia, Costa Rica, Ecuador, Guyana, Panama, Venezuela, and Nicaragua have either undertaken or are considering operational vampire bat control programs.

Under an Environmental Protection Agency (EPA) contract, we evaluated the hazards associated with strychnine baiting for pocket gophers (Geomys bursarius) with the burrowbuilder. On the Sherburne National Wildlife Refuge, Minnesota, we treated 662 ha (1,638 acres) with 0.5 percent strychnine-treated bait. Treated fields were scattered throughout 10 sections. Control was effective--data from pocket gopher activity plots showed 87.5 + 5.9 percent reduction in activity. Populations of other small rodents (while quite low) significantly declined on the treated area, but significantly increased on the control area. To measure secondary effects we equipped 36 raptors and 36 mammalian predators with radio transmitters. We detected little, if any, effect on radio-equipped raptors and mammalian predators. Red-tailed hawks (Buteo jamaicensis) , American kestrels (Falco sparverius), great horned owls (Bubo virginianus), badgers (Taxidea taxus), striped skunks (Mephitis mephitis), red fox (Vulpes fulva) and a coyote (Canis latrans) were intensively radio-tracked during treatment; those that utilized treated fields all survived. Mammalian predator tracks and diggings were frequently observed on the burrow-builder tracks after treatment. Red-winged blackbirds (Agelaius phoeniceus) were selected as a representative of seed-eating birds. We marked 100 territorial males on both the treated and control area and monitored them during the treatment. Even though some treated grain was available on the surface and marked birds were observed feeding in treated fields, we did not detect any detrimental effects. Nevertheless, we found one treatment-killed mourning dove (Zenaida macroura).

The training program was started in 1973 for students in Advance Agriculture Occupations classes. Several state and federal agencies were involved in the planning and have since been involved in the training program. The program stresses the practical approach with a variety of field work and related classroom work. Classroom work covers all problems involved in animal damage control. The program is still in the innovative stage, but it seems to be fulfilling a need.

The pine vole (Microtus pinetorum) damages apple trees in western North Carolina, sometimes spectacularly. The current research monitors populations in orchards for several years to compare damage in different management practices. Recommendations for orchard management to reduce damage are devised and used to illustrate the process of application of basic knowledge. Populations of voles were monitored by 3 simple methods. Data on reproduction were obtained. Data on home range and mortality were found in the literature. In two counties, the orchards generally had grass in the alleys and sometimes a growth of weeds under the tree canopy. In two other counties (less hilly) the orchards were much cleaner. Numbers of voles and amount of damage were much higher in the less clean orchards. A management program should include mowing 5 times a year, clearing vegetation from under the tree, removing prunings, restricting distribution of fertilizer and, after harvesting, inspecting and cleaning especially vulnerable parts of the orchard.

The conservation of Egyptian wildlife is discussed. Control measures are reviewed for rodents and birds, especially the house sparrow. Because of the high dam, permanent irrigation has resulted in Arvicanthis becoming a more serious invader of rural buildings.

Studies in urban areas have shown that food and shelter are primary environmental factors regulating rodent population growth. These supportive resources can be modified to reduce urban rodent damage; however, widespread adoption of environmental control techniques will require a thorough understanding of rodent-man interrelationships. This study was concerned with what factors should be monitored for making rational ecological decisions on the necessity of rodent management, establishment of priorities, choice of appropriate strategies, and evaluation of effectiveness. Guidelines are given for comprehensive monitoring of habitats (social, structural, and sanitary factors) and rodent populations (habitat requirements, growth characteristics, and zoonosis potential).

An attempt was made to identify the olfactory cues produced by Douglas-fir seeds which attract deer mice (Peromyscus maniculatus) to the seeds. The olfactometers used are described, and the merits of different statistical analyses of the data are discussed. The odors produced by whole Douglas-fir seed and by the endosperm were preferred among the fractions tested to date. Deer mice were repelled by Douglas-fir turpentine, cedar oil, and, to a lesser degree, one extract.

Deer and reforestation interact mainly during regeneration after wildfire or logging. In interior forests, browsing by mule deer often damages conifer seedlings planted on winter or transitional ranges. In the Douglas-fir region, numbers of blacktailed deer increase dramatically after forests are logged or burned, in response to improved forage supplies. Here, browsing on planted stock in clearcuts lowers forest productivity by reducing growth rates and occasionally contributes to plantation failures. Browsing damage can be controlled by fences or cages, but costs are prohibitive. Amelioration of damage by black-tailed deer could be achieved through long-range planning for concurrent deer and timber harvests, with hunting pressure directed to areas where logging promotes more deer. Thus, more deer can be made available to hunters and browsing damage to reforestation lessened. Such programs would require complete cooperation among resource managers and an intensive, well-planned effort to sell them to both customers and critics.

Four individually penned coyotes (Canis latrans) that had learned to kill live domestic rabbits for food were presented with one black and one white rabbit during daily 1-hour sessions and punished by a brief, severe shock from a high-voltage collar each time they attacked the black rabbit. One coyote did not learn the color association; after three shocks, it refused to kill either rabbit for 10 days but killed both indiscriminately when retested 4 weeks later. The other three coyotes learned to avoid black rabbits after only three to five shocks and, when repeatedly retested without shock at several-week intervals, did not begin killing them again until 3 to 9 months later. These animals' rapid acquisition and long retention of an avoidance response to a certain class of prey suggests a potential for aversive stimuli to reduce coyote attacks on livestock.

Predictive and conceptual models are used to examine the contamination, toxicology, and residues of sodium fluoroacetate (Compound 1080) in relation to its application in vertebrate pest control programmes on forest and pastoral lands. As a pesticide, the toxin appears to be neither mobile nor persistent. Exceedingly slender opportunities exist therefore for significant contamination of susceptible components of the environment.