Proceedings of the Vertebrate Pest Conference

In this Keynote Address, the author focuses on the USDA APHIS’ document “Strategic Plan for Animal Damage Control,” released in December 1989. The document results from a 2-year strategic planning process, produced as a product of collective expertise among ADC management and staff, cooperators, and collaborators. It will guide the federal ADC program for the next 3 to 5 years, and in doing so will strongly influence the whole arena of vertebrate pest management in the U.S. A Mission Statement is described and discussed. Critical issues addressed include: 1) lack of an effective system of management practices; 2) failure to adequately maintain or improve control tools and techniques, or to develop new methods; 3) inadequate investment in major capital assets; 4) failure of wildlife damage management to be recognized as a critical component of wildlife management; and 5) a lack of critical data on wildlife damage and control actions, benefits, and impacts.

The relationships between man and other animals have attracted increased attention and some controversy in recent years. Their importance in biomedical research, farming, and wildlife control are discussed in the United Kingdom context.

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) was amended in 1988 to require the reregistration of all pesticides registered before 1984 within 9 years. The FIFRA 88 required that all pesticide active ingredients must meet current registration standards, suspended the previous fee structure, and imposed a one-time registration fee and annual maintenance fees. New data generated because of FIFRA 88 must conform to EPA's Good Laboratory Practice Standards and animal studies must follow guidelines of the Animal Welfare Act. FIFRA 88 has significantly increased data requirements, data costs, and other pesticide registration and reregistration costs for most pesticides. The increased financial burden has caused industry and governmental agencies to drop minor-use registrations that could not generate sufficient profit to pay for reregistration. During 1989, over 19,000 pesticide registrations were canceled because of the imposition of annual maintenance fees levied by FIFRA 88. More registrations will be canceled in 1990 as registrants find that it is not cost-effective to provide data for many minor-use pesticides. This will result in the loss or further use restrictions on chemicals critical to manage vertebrate pests. In addition, the reregistration process will divert funds from research on alternative pest management practices at a time when that research is critically needed.

Controlling vertebrate species obnoxious or even dangerous to them has been a concern of the human species through the evolutionary process. Early measures were often based on religious, superstitious, and biologic fantasies. While modem control measures are better biologically founded, there still remains an aura of mythology around many accepted by the public today. Examples are given of some of them: toxicants, electromagnetics, ultrasonics, and repellents for deer, moles, and raccoons.

The field of prevention and control of wildlife damage is changing and evolving along with clientele needs, pressures from user and non-user groups, and other factors. A theoretical overview of the field may offer an action model regarding changing trends and potential responses. I propose that three things happen every time a wildlife damage problem occurs: 1) A human activity, desire, or need is interfered with, 2) the experience footers an opinion about a wild animal usually negative, and 3) a decision is made to tolerate the situation or to control it. If control is selected, availability and effectiveness of prevention and control techniques become feedback mechanisms that may affect tolerance of damage; threshold levels at which control is initiated; and opinions about damage control, wild animals, and natural systems. Wildlife damage professionals might use these concepts in responding to enhance the public understanding and professional image of the wildlife damage field.

Wildlife management has evolved through a series of stages, with early efforts directed toward individual species. Since the late 1800s, however, more wildlife applications have incorporated a systems approach, where communities are managed to promote the quality, quantity, and fitness of most associated species. Vertebrate pest management has followed a similar course of development, although it has lagged behind in addressing the concept of systems management. I propose that a systems approach to vertebrate pest management should include the consideration of all potential problem species of an area or situation and should integrate damage prevention and control strategies that minimize damage caused by those species identified as economically or socially detrimental. The systems approach can provide long-term benefits and is therefore generally cost-effective. It works in accordance with integrated pest management principles and proactive interdisciplinary programming and can be incorporated into agricultural profitability and sustainable agriculture initiatives. Examples where the systems approach to vertebrate pest management could be feasible are provided.

The State Department of Conservation, Forests and Lands (CFL) administers legislation relating to the management of pest animals and plants throughout Victoria. CFL conducts control work on public land and assists landholders with programs on freehold land. To provide an information base for the management of CFL's pest control programs, the Pest Management Information System (PMIS) was developed. The PMIS captures descriptions of pest infestations, details of planned and actual treatments, and evaluations of treatments. The first version of the PMIS, developed for microcomputers, was released in 1987 and underwent minor revision during 1988 in the light of field experience. During 1989 the PMIS was redeveloped using in-house computer prototyping tools on CFL's statewide computer network. It is currently being trialled in two regions prior to wider implementation. Initial results from the pilot trials indicate that the PMIS will in time become a valuable tool in the management of pest animal and plant problems in Victoria.

The United States Department of Agriculture (USDA), Animal and Plant Health Inspection Service (APHIS), Animal Damage Control (ADC) Management Information System (MIS) is in the process of being updated to a relational database format on an IBM-compatible microcomputer. The background of the MIS, the development process, the information that is collected, how the information is used by program managers, and the coot benefits of the automated system are addressed.

The balance of nature requires a balanced predator-prey relationship. In agriculture or urban areas the natural predator-prey balance is disrupted because the habitats have been altered and, for the protection of livestock (and for humans in case of grizzly bears, lions, and wolves), the large carnivores have usually been displaced. Consequently, in these altered environments to prevent crop depredations, to keep other vertebrate species in balance with their environment, and to protect some endangered species, people must manage the wildlife. This often means that for the welfare of animals people have to become predators to assist nature. Fortunately, from an animal welfare point of view, people are usually a more humane predator than nature because they operate under regulations designed to minimize suffering. While animals and their antics can be beautiful, the way predators capture and kill prey is often inhumane and brutal. Therefore, animal control operations, as currently undertaken with rodents, birds, and predators, frequently play both a beneficial and a humane role. Without such controls, there is often much more suffering through starvation, disease, etc. Also, much animal damage control is pest prevention, thus reducing the former need for toxic chemicals and lethal approaches

To reduce the costs of providing development assistance in agriculture to the people in the Developing Countries, an international "Post-Harvest Agriculture Computer Teleconference" has been available now for more than 15 months. Suitably supplemented with electronic computer communications networks and their E-mail, these tools allow relatively inexpensive assistance. This combination offers many advantages to the organizations offering assistance and those needing help.

In the western United States, Lyme disease has been reported primarily from the three Pacific states, especially California, and sporadically or not at all from various mountain states. In California, surveillance for Lyme disease was initiated in 1983, but it was not made a reportable disease in this state until 1989. Nevertheless, approximately 400 human cases were reported by California State Health authorities between 1983 and 1987. In 1982, I began studying the ecology and epidemiology of Lyme disease in the far-western United States in collaboration with Dr. Willy Burgdorfer of the Rocky Mountain Laboratories, Hamilton, Montana, and others. The objectives of this research have been to determine how the Lyme disease spirochete, Borrelia burgdorferi (Bb), is maintained and distributed in natural foci including the routes of transmission to humans and other animals. Five species of ticks have been found infected naturally with Bb or related borreliae during these studies, but of these only the western black-legged tick, lxodes pacificus, has been implicated as a vector to humans. Transovarial and transstadial passage of Bb has been demonstrated in this tick, though the efficiency of these processes for maintenance of the spirochete is still being evaluated. Western fence lizards (Sceloporus occidentalis) and Columbian blacktailed deer (Odocoileus hemionus columbianus) were found to be major hosts of subadult and adult I. pacificus, respectively. Antibodies to Bb, spirochetemias, or both, have been detected in 8 species of wildlife in California (western fence lizard, 2 species of lagomorphs, 2 species of rodents, 3 species of deer). Species exhibiting the highest seropositivity rates (titers ≥1:64) include brush rabbits (≤100%) and black-tailed jackrabbits (≤90%). The widespread distribution of jackrabbits in the West, their prolific breeding habits, infestation by several species of ticks known to harbor Bb, and their high seropositivity rates render them suitable as sentinel animals for surveillance of Lyme disease. The reservoir competencies of some of these species of wildlife including Columbian black-tailed deer, and the vector competencies of their associated ticks, are currently under investigation.

Beginning in the 1960s, labels for federally registered commensal rodenticides have been required to bear a statement to the effect that the baits are to be contained in "tamper-proof bait boxes" when used in locations available to children and nontarget animals. Faced with ample evidence of noncompliance with the letter and spirit of this portion of the label, the U. S. Environmental Protection Agency {EPA) issued a policy statement (PR Notice 83-5) and scheduled public hearings on matters pertaining to bait stations and nontarget exposure incidents involving rodenticides. EPA's findings indicate that, while some clarifications of its policies might be helpful to rodenticide users and to bait and bait station manufacturers, the historical requirements for bait protection have been appropriate and necessary. Additional steps and incentives appear to be needed to increase the extent of compliance with label requirements for use of protective bait stations and thereby reduce the incidence of exposures of young children, dogs, and other nontarget organisms to commensal rodenticide baits.

An increasing trend in the frequency of human bubonic plague cases in the United States, the principal sources of human Infection, and emerging control techniques are described. Development of an integrated control program involving public health education, citizen participation in plague surveillance, and insecticidal control of flea vectors in response to evidence of plague and potential human exposure substantially reduced human plague cases in a Bernalillo County, New Mexico, hyperendemic plague area. Permethrin 0.5% dust (Pyraperm 455) applied at a rate of 7 g per burrow was found to provide effective control of flea vectors for at least 6 weeks.

Exposure, as well as toxicity, determines whether rodenticides present real environmental hazards to nontarget animals. In order to combine exposure and toxicity, a compartment model is proposed which distinguishes transfer processes from accumulation of residues. The published literature relevant to the model is analysed, and some important gaps in knowledge are highlighted. Simple sub-models of rat feeding behaviour and mortality are combined into a simulation model which generates data on both efficacy of control and build-up of residues in live rats and carcases. The roles of feeding parameters (e.g., palatability, availability of alternative food) as well as toxicity are emphasised by the simulation results.

The compound bromethalin is described and characterized in terms of mode of action when used as a rodenticide. It is hypothesized that an antimetabolite which inhibits the conversion of bromethalin to its desmethylbromethalin metabolite could represent a potential treatment for bromethalin toxicosis. An ideal antimetabolite of bromethalin is described, and based on these considerations, aminophylline (theophylline ethylenediamine) was chosen as a potential antimetabolite. In lab trials, aminophylline was administered to rats given a lethal dose of bromethalin, but it was not effective in prolonging rat survival. However, it did result in mean survival time being increase to nearly double. Further studies aminophylline or similar drugs may results in identifying a suitable treatment for bromethalin-induced toxic syndrome.

Vertebrate pest control measures may have an impact on nontarget wildlife. Bird and rodent control programs using avicides and rodenticides in California have been, and are currently being, examined by the California Department of Fish and Game on a routine basis. Each pesticide used has its deleterious side effects. This paper reviews these side effects and suggests possible future impacts which could be expected.

Advances in the process of microencapsulation over the past two decades are described, as are the proposed reasons why it may be desirable to microencapsulate rodenticides. However, recent attempts have resulted in problems such as poor bait acceptance, poor palatability, excessively rapid toxic action, or reduction in toxicity. One researcher, after trials with 4 rodenticides and multiple materials used as coatings, reported that most lab trials resulted in increased consumption of the active ingredient, but they rarely resulted in improved kill of the rodents beyond the biological variation normally found in groups of laboratory animals. Taste and/or odor-masking are the research objectives most often pursued in rodenticide microencapsulation, followed by a goal of delaying the release of the toxicant in the gastrointestinal tract. However, we lack of biological knowledge of the feeding mechanics and digestive physiology of various pest rodents; for example, the site(s) of absorption of toxicants or toxic metabolites is not known for some rodenticides and rodents, thus inhibiting our ability to tailor the onset of symptoms or toxicosis. Potential disadvantages of microencapsulation are listed, which could lead to increased risks to nontarget species. Recent studies involving microencapsulation of several rodenticides are summarized.

A comprehensive rodent control program is being planned for a $4.4 billion highway-construction project in Boston, MA. This IPM program will include broad participation by project personnel, city and state agencies, and community groups. Surveys, public education, and sanitation improvements will begin more than a year before construction; baiting will begin approximately 3 months before construction. All control activities will be maintained until construction is complete. Mitigation of community impacts during construction projects is a growing concern, and improved approaches to construction-related rodent control are needed.

Constant developments in technology, both materials and methods, allow smaller and smaller animals to be radio-tracked for longer periods of time than was previously possible. Developments in electronic component miniaturization and battery chemistry are primarily responsible for this advancement. Approximately 30 years of field-use of radiotelemetry techniques have led to innovative procedures and uses of materials for the application of transmitters to animals. New technology such as satellite telemetry and recapture collars are only in their infancy and are not, at this time, appropriate for use in vertebrate pest research. Sophistication in receiving systems also allows more accurate and more complete data to be collected. This paper is not intended to be a review of telemetry devices on the cutting-edge of technology or non-field-proven developmental systems, but rather presents an overview of currently available, on-the-market technology appropriate for use by vertebrate pest researchers. As it is a review paper, not a research paper, it does not strictly follow the standard research paper format.

Pocket gophers were collected from irrigated alfalfa fields (IRR) and non-irrigated fallow fields (NIRR) in Davis, California, for 2 years. Reproduction was continuous in IRR fields with very little seasonal variation in reproductive activity. In contrast, reproduction in NIRR fields occurred primarily during the rainy season (winter and spring). Females in IRR fields produced approximately twice as many litters per year (3.6-3.9) as females in NIRR habitats (1.7). The high reproductive potential of adult females in IRR fields coupled with the early age of sexual maturity among young females suggests that population recovery after control measures is likely to be relatively rapid in irrigated alfalfa fields. Immigration into the optimal habitat of irrigated alfalfa fields is also likely to add to rapid recovery if gopher populations in nearby areas are not controlled as well.

Laboratory tests, field telemetry trials, and actual use field efficacy evaluations showed that a 0.5% strychnine alkaloid steam-rolled oat-groat hand-bait formulation (EPA Reg. No. 56228-20) with molasses, salt, glycerine, and soda was effective in controlling northern pocket gophers (Thomomys talpoides). Baits retaining at least 0.5% strychnine (w/w) were as effective (>95% control) as baits with 0.75% and 1.0% strychnine in field telemetry hand-baiting trials as well as operational hand-baiting and burrow-builder baiting field tests in forest habitat. Data indicated that the 0.5% strychnine hand bait (molasses formulation) should be reregistered and would be a good substitute for the 0.5% strychnine-Rhoplex bait (EPA Reg. No. 5622812) currently registered for burrow builder use for pocket gopher control. Both the retention of strychnine on bait and use of a highly palatable top quality bait carrier were two important factors affecting efficacy of the bait.

Four adult female Botta's pocket gophers (Thomomys bottae) that had survived many normally potentially lethal doses of strychnine alkaloid in another experiment (Lee 1986) were examined further. These individuals freely consumed 0.5% strychnine bait, and 3 of them also 1% strychnine bait, for long periods without dying, whether or not nontoxic alternate bait was present. After 1 gopher (#5) was taken off its 1% strychnine wheat diet for 44 days, it lost its physiological tolerance to strychnine and died the first day when again exposed to a free choice of nontoxic and 1% strychnine wheat. It consumed only 7 mg/kg of strychnine before dying, whereas another gopher (#42) was able to survive on a mean daily consumption of 275.8 mg/kg of strychnine in a no-choice situation over a period of 28 days. This is almost 40 times the lethal dose of the other animal.

Two field trials were conducted to determine the effectiveness of anticoagulant baits in pocket gopher (Thomomys bottae) control. In the first trial, burrow systems were baited once with chlorophacinone 0.005% on rolled oats and embedded in paraffin to form a wax block. The systems were arranged in a one systemwide line bordering a clean vineyard. Infestation of the vineyard was prevented for 2 months; after that, gophers did bypass the barrier of treated systems and entered the vineyard. In the second trial two anticoagulant baits, chlorophacinone 0.005% on rolled oats and embedded in paraffin, and diphacinone 0.0052% on various grains and embedded in paraffin, were compared to strychnine-treated 0.29% whole wheat grain bait. Fifteen individual gopher systems were baited in each of three replications and monitored for 8 1/2 months. Both of the anticoagulant paraffin block-type baits achieved significantly greater long-term gopher control than the strychnine-treated loose grain bait.

We evaluated the ability of underground fencing to exclude pocket gophers (Thomomys bottae) from experimental plots planted with alfalfa. Fencing extending 61 cm below and 91 cm aboveground, with a 15.2-cm lip bent 90 degrees inward at the bottom, did not prevent marked and unmarked gophers from escaping, invading, or moving among six adjacent plots. Complete underground screening, in combination with gopher control, may be the only technique which ensures the complete exclusion of gophers from experimental and ornamental plots.

Rapid reinvasion of low-density sites by dispersing ground squirrels often results in short-term benefits from otherwise effective population control methods. Existing vacant burrow systems appear to play an important role in facilitating the local population recovery. The potential of destroying the ground squirrel burrow entrances to reduce site reinvasion, following population removal, was tested. Under the conditions of the tests, deep ripping resulted in >85% reduction in burrow reinvasion by California and Belding ground squirrels. Studies are still in progress to evaluate the consistency of the results and include long-term effects and cost information. The inclusion of this technique into the management of crops rather than the management of one pest species alone is discussed.

The African striped ground squirrel, Xerus erythropus (E. Geoffroy), has been found to constitute a serious pest to maize seed at the planting stage, causing mean losses of 9.7% and accounting for 57.3% of total damage found. A feature of ground squirrel damage is its unpredictable nature. Methods of reducing looses of planted maize seed to X. erythropus at the subsistence farmer level in southern Kenya were investigated. Constraints affecting a control programme by farmers were identified as follows: low standards of living and education, limited financial resources, strong individualistic attitude of farmers and small field size in relation to the home range size of squirrels. Removal trapping and poison baiting were selected for trial as meeting requirements of ease and simplicity, and involving materials available to farmers at the time. Field trials of bromadiolone and difenacoum anticoagulant rodenticides and removal trapping over periods of 1 month and 3 months prior to the expected onset of the rains failed to affect damage levels significantly on individual field units. Underbaiting and a high reinfestation rate were considered to be the primary causes of failure, and the habit of scatterhoarding exhibited by X. erythropus further complicates the poison baiting trials. The unpredictable nature of ground squirrel attack discourages farmers from expending valuable resources on control. Alternative strategies for farmers are discussed.

A study to determine the relative effectiveness of three trap types for Columbian ground squirrel (Spermophilus columbianus) removal was conducted during May and July 1985 in Missoula County, Montana. A Two-way Analysis of Variance was used to test for differences in reduction of burrow activity between conibear, box, and live traps versus controls. All trap types significantly reduced ground squirrel activity when compared to the controls for each month, but no trap type was significantly more effective than the others. Ground squirrels are more easily caught in July; trapping during both months is recommended for maximum reduction in ground squirrel populations.

Three subspecies of the California ground squirrel (Spermophilus beecheyi) were studied. In the first test of Experiment 1, Beechey (S. b. beecheyi), Douglas (S. b. douglasii), and, for comparative purposes, Sierra (S. b. sierrae) ground squirrels were each offered a drinking tube containing one of three H20 solutions of strychnine sulfate (0.01, 0.05, or 0.5%) after being deprived of water for 23 hr. In Test 2 the survivors of Test 1 were offered for 24 hr a free choice of distilled water and two of the above concentrations of strychnine solutions. In Test 3 the survivors of Test 2 were offered for 24 hr a free choice of the same three concentrations of strychnine, but plain water was available. In the three tests, lethal amounts of strychnine solutions were consumed by 11 (79%) of the Douglas, none of the 14 Beechey, and 2 (18%) of the Sierra ground squirrels. In Experiment 2 the Douglas ground squirrels again proved to be the subspecies most susceptible to strychnine when compared with Beechey. In a third experiment, the squirrels did not reject strychnine bait on the basis of odor; however, in the fourth experiment Beechey ground squirrels that had been trained to reject strychnine-treated oat groats, a preferred grain, subsequently displayed much less interest in the olfactory cues from oat groats, suggesting that both previous experiences and olfactory cues are relied upon, at least in part, in their subsequent rejection of toxic food, even though strychnine sulfate may be odorless. These data help explain some of the problems associated with the use of strychnine as a rodenticide for the Beechey ground squirrel.

A review of currently registered vertebrate pesticides is reported with by far the major weight given to strychnine and 1080. The author searched the Agency's label files and has listed most of those pesticides that have claims against at least one vertebrate animal.

A survey of alfalfa bay producers was conducted to characterize vertebrate pest problems in Nevada alfalfa hay and help attract research funding. Damage to alfalfa bay by pocket gophers (Thomomys spp), ground squirrels (Spermophilus spp), black-tailed jackrabbits (Lepus californicus) and meadow voles (Microtus montanus) was assessed. Presence of vertebrate pests along with a ranking of cost-related problems they pose to alfalfa hay operations was determined. Pocket gophers were the most costly pest followed by ground squirrels, jackrabbits, and meadow voles. The number one problem caused by vertebrate pests was identified to be a decrease in hay production. Control techniques were rated as somewhat effective for all rodent and rabbit pests. The costs associated with farm management practices were ranked from highest to lowest in this order: irrigation, rodents and rabbits, weeds, insects, and fertilization.

Rattus norvegicus, R. exulans, and R. rattus cause extensive damage to Hawaiian sugarcane. This paper gives an overview of the problem and briefly summarizes the history of rodent control on Hawaiian sugarcane plantations. Current baiting practices with zinc phosphide may favor the proliferation of R. norvegicus, and more effective control methods are needed for this species. A cooperative research and development program by the Denver Wildlife Research Center and the nonprofit Hawaiian Sugar Planters' Association is described.

After crop losses of 5 to 60% were noted on two 500-acre Jojoba (Simmondsia chinensis) plantings in a desert area of southern California, a study was conducted to identify the animals responsible. Various population census and pest identification techniques were utilized. Four native rodents of the Heteromyid family, not previously known to be pests of Jojoba, were found to be present in sufficiently high numbers to cause severe economic crop loss. The Bailey's pocket mouse (Perognathus baileyi) was the only rodent previously known to survive on Jojoba beans as a food source. A natural chemical, cyanogenic glucoside, was thought to be the plant protective material responsible for previous failure of rodents to survive on Jojoba in field and laboratory studies. Most of the rodent species found in this investigation were also observed in the laboratory and survived on a ration consisting almost entirely of Jojoba beans for 6 to 10 months. The ability of these rodents to survive on Jojoba beans suggests the possible co-evolutionary development of detoxification mechanisms. Cultural and population reduction practices were recommended and implemented following this study resulting in greatly reduced crop losses.

Rattus tiomanicus is a serious pest of oil palm plantations in Peninsular Malaysia, feeding on the ripening fruit. R. diardii is a rat of human habitations and has been only an occasional field species, presumably because it cannot compete with better adapted species. A widely used control for R. tiomanicus of proven effectiveness uses maize-based baits containing warfarin at 0.05% in 2 cm3 (14.5 g) wax-bound cubes. These are applied in campaigns at one per palm, replaced on 4 daily rounds, until acceptance has declined to 20%. This "standard method" is applied at about 6-month intervals, and rat populations remain low. In the early 1980s resistance to warfarin began in R. tiomanicus, and from about the same time R. diardii was found more often in oil palms, apparently in the same localities. This review is of studies of these phenomena. Rat population studies by mark, release, recapture (MRR) confirmed that warfarin baiting was failing against R. tiomanicus, or required prolonged application, whereas second-generation anticoagulants (brodifacoum, bromadiolone, and flocoumafen) were effective. Physiological resistance was confirmed in the laboratory. Direct substitution of second-generation compounds increased the cost of control considerably, and ways to reduce costs were investigated. Smaller bait size presented problems in monitoring bait acceptance, and longer intervals between replacements did not reduce consumption. Half the active ingredient concentration had some promise, but a first-round application of one bait per two palms was most practicable. Bromadiolone baits at 0.005% are now used at half density of one bait per two palms on the first application in areas of warfarin resistance. Where the problem was first noted, rat populations were compared in areas with and without continued baiting. In an 81-ha plot left unbaited, R. diardii gradually increased and replaced R. tiomanicus during 1982-84. R. diardii then remained predominant until 1989. In the baited plot, once bromadiolone was used (from early 1984) both species were controlled. It is postulated that R. diardii became able to out-compete R. tiomanicus because the genotype of the latter had somehow been weakened in the rapid selection for warfarin resistance.

During 3 years we studied a population of multimammate rats, Mastomys natalensis (Smith 1834), in Morogoro, Tanzania. Data were collected in both removal and capture-recapture schemes. We present evidence that patterns of growth and reproduction were related to onset and abundance of rains. This partially explains differences in densities. Additionally, we investigated available literature data and related them with climatological data. A scenario is presented which enables us to predict how densities of multimammate rats may evolve in the following year and whether there will be a risk of outbreaks. The use and implications of this scenario in planning control actions are discussed.

The control of the Mediterranean pine vole through manual bait placement is too fastidious. It prevents the realization of collective control on large areas. In this situation, mechanization is necessary. A burrow builder, made of a tubular ploughshare, has been devised in order to make artificial runs in the soil where baits may be deposited. This plough was successfully tested in fall 1989 in apple orchards with a wheat-based bait treated with chlorophacinone, chosen for its good resistance to moisture. The treatment efficiency varied between 86.7% and 96.4% with 25 and 50 artificial runs per hectare, respectively. A humid but well-dried-out (i.e., moist but not wet) soil is the necessary condition for successful treatments so that the runs may not collapse. New tests with other types of baits in other crops overrun by the Mediterranean vole are necessary to confirm these results.

Artificial perches and nest boxes were placed in three Pacific Northwest orchards to assess their effectiveness in attracting birds of prey to reduce vole populations. The data indicated that birds could be attracted under some conditions but vole populations were not significantly affected. Additional factors such as vegetative biomass and human activity may limit their usefulness in reducing rodent populations under intensive agricultural conditions.

Rodents, one of several kinds of vertebrates included in the human diet, are very suitable as human food. More than 71 genera and 89 species of rodents, mostly hystricomorphs, have been consumed by man. Some have even been domesticated for private or commercial production of food for human consumption. Rodents in the temperate world serve only as a supplement to the regular diet of humans; but in the tropical world, they are widely accepted and a popular source of protein. Although harvesting field rats for human food is beneficial, it is not an effective pest control strategy. Consuming rodents in pesticide-treated areas and handling rodents with potential zoonoses are two possible risks.

Requests for assistance, monetary losses attributed to wildlife, and numbers of wild animals removed from urban areas in California increased significantly between 1982 and 1989. Five species of wildlife are responsible for the majority of complaints received from the public. Because of the inherent problems associated with animal damage control in densely populated urban areas, specialized control equipment and techniques such as cage traps, crossbows and night vision goggles are utilized by U.S. Department of Agriculture, Animal Plant Health Inspection Service, Animal Damage Control (USDA-APHIS-ADC) personnel. Urban ADC programs help educate a large segment of the population about the need for occasional control of problem wildlife.

Rabies is currently enzootic in many cities of southern Ontario. The Ministry of Natural Resources is utilizing two different tactics for the control of rabies in urban wildlife rabies vectors − rat immunization with baits (foxes) and vaccination by injection following live-capture (skunks and raccoons). Between 47 and 79% of the skunks and 61 and 76% of the raccoons were captured and vaccinated (Imrab) in a 60-km2 urban area of Metropolitan Toronto during 1987, 1989. Only three cases of rabies in skunks have been reported since control began in 1987. Population increases of 120% for skunks and 40% for raccoons were noted since the rabies control program was initiated. Densities for raccoons and skunks in urban habitat were found to be as high as 56 and 36 per km2, respectively. An estimated 56% of the foxes in Metropolitan Toronto were reached with rabies vaccine baits following distribution throughout the ravine systems and at fox pup-rearing den sites. To our knowledge, this is the first documentation of the use of a live-virus rabies vaccine for the control of fox rabies in a large metropolitan environment.

Various frightening stimuli, primarily visual and acoustic, have been used to prevent or alleviate damage by depredating mammals (e.g., deer (Odocoileus spp.), raccoons (Procyon lotor), tree squirrels (Sciurus spp.), coyotes (Canis latrans). Frightening methods are most appropriate for use where a crop or situation needs protection from pest mammals for only a period of a few days or weeks. The ability of animals to habituate to such stimuli limits their long-term usefulness. Against nocturnal species, various types of lights and noisemakers are the most useful. Combining acoustic and visual stimuli can enhance effectiveness, while varying the techniques used, the placement of frightening devices, and/or the timing sequence can delay habituation. Other types of physical frightening stimuli are also reviewed.

Protecting individual plants or small clumps of plants with some type of protective material or device represents a positive nonlethal approach to damage prevention that is often much less expensive than fencing an entire garden or crop or netting over the entire area to prevent damage by such species as deer (Odocoileus spp.), rabbits (Lepus spp., Sylvilagus spp.), and ground squirrels (Spermophilus spp.). This review article does not include fencing or the netting or screening of entire crops, which are subjects unto themselves. Tree trunk guards or protectors include commercial tree wraps and other materials affixed directly to young tree trunks, wire cylinders for individual trees, and plastic-mesh tubing. The use of soil mounding or a layer of coarse gravel around the base of a tree is helpful against damage from meadow voles (Microtus spp.). Damage from pocket gophers (Thomomys spp., Geomys spp.), can be alleviated by planting in wire-mesh cylinders or baskets, although generally too expensive and impractical to be used for large commercial plantings. Tree bands and shields are particularly useful against ground and tree squirrels (Sciurus spp.) and certain other climbing mammals. For seeds and very young seedlings, domes, caps, and cones offer good protection during their vulnerable period. Where other materials are scarce, the use of prickly or thorny plant materials, such as holly or hawthorn branches, can provide protection to newly planted seed and young seedlings. This paper reviews these methods and provides references for those seeking further information.

The status of damage by vertebrate pests to growing and stored agricultural crops is reviewed in the light of changing patterns of agricultural practice and land use within the UK. Significant problems and existing management techniques are briefly discussed. The results of recent research by the Agricultural Department and Advisory Service (ADAS) of the Ministry of Agriculture, Fisheries and Food are explored to indicate the future direction of vertebrate pest management to reduce crop damage. Recent changes in legislation and public altitudes impose constraints on some of the approaches to solving problems. The continued role of traditional control methods is considered together with new opportunities and requirements to exploit the ecology and behaviour of pest species in order to reduce damage.

Seed predation by rodents has limited successful re-establishment of desirable shrubs, forbs, and grasses on degraded western rangelands. We need to develop methods that temporarily reduce rodent numbers or their predation of planted seed if we are to establish diverse rangeland plant communities. Range site conversion treatments of chaining, prescribed burning, spraying, or drilling have not been effective in reducing deer mice populations. However, seed predation has been reduced by adopting seeding strategies that mimic natural seed predation avoidance mechanisms. Seedings have been designed to mimic the "satiation" strategy for plant establishment by providing more seed and sacrifice foods than can be utilized by the resident rodent population. Seed has been planted in the spring when rodent populations are low, seed has been buried to hinder location, and seeded species have been selected for low rodent preference. Chemical repellents and rodenticides have also enhanced seeding success, but environmental concerns have limited their application.

A questionnaire survey of the National Forests in 1988 indicated that animal damage control (ADC) was conducted on 208,000 acres of reforestation and older stands, nearly all in the West, at a cost of about $9 million. Sixty-two percent of the total acreage treated, or 128,600 acres, and 49 percent of the ADC costs, or $43 million, was in the Pacific Northwest Region (Oregon and Washington). Most of the forests in all regions of the Forest Service, except Alaska, rated animal damage to reforestation and older stands as very important or moderately important. One-third of the forests rated damage as increasing, about two-thirds rated damage as about the same, and only 6 percent rated it as decreasing. Damage to forest stands was caused by a wide variety of animals, including livestock, but pocket gophers (Thomomys sp.) were the single most destructive group of species on National Forest System (NFS) lands. More than half the forests reported animal damage to structures and campgrounds or animal-related health hazards such as rodent-borne diseases. Beaver (Castor canadensis) were a minor problem in all regions and were reported as causing damage by about one-third of the forests. In addition to significant and increasing black bear (Ursus americanus) damage to young stands, bear depredations and nuisances were reported by half of the forests in all regions except Alaska. Two-thirds of the forests reported an ongoing need for ADC training. Forests reported ADC research needs in every region except Alaska.

Certain mammals and birds may damage or destroy southern pines, causing economic losses in intensively cultured areas such as seed orchards and nurseries. Mammal pests may eat seeds; tunnel, dislodging seedlings, or chew on roots; or girdle, debark, or sever stems or branches. Bird pests may eat seeds or excavate holes in the tree trunks. The first important step is to identify the pest(s) from the damage left behind. Thereafter, various control options−from using traps and repellents to altering habitat−are available.

The severity and extent of browsing damage to pine and eucalypt plantations and possible solutions are examined. Twenty-six percent of all trees surviving 9 months after planting were browsed yet only six percent had more than 50% of foliage damaged. The most common form of damage was for the foliage to be browsed or the tree bitten off with browsing damage implicated in the mortality of the 24% of trees that died. No difference in the extent of damage between Pinus radiata and eucalypts was detected. Slight differences between three Eucalypt species and two ages of seedlings were detected; however, these differences in damage levels were insufficient to afford adequate protection through appropriate selection of species and type of nursery stock. Most of the damage was attributed to the Swamp Wallaby (Wallabia bicolor) and the European rabbit (Oryctolagus cuniculus). The use of electric or rotonet fencing and repellents containing chili or dog-urine extracts seem to offer the only nondestructive ways of minimising browsing damage. The development of less palatable species and types of nursery stock is dependent on other considerations including general suitability, but warrants further research.

A combination of factors are responsible for mortality in conifer plantations. Ponderosa pine (Pinus ponderosa) were planted on 3 transitory ranges in northern and central Idaho. These plantations were followed closely (sampling up to 7 times per year) for 6 years recording the causes of mortality and damage to the tree seedlings. Pocket gophers (Thomomys spp.) killed the most trees (71%) while nonanimal causes killed 21%. Elk (Cervus elaphus) and deer (Odocoileus spp.) killed a maximum of 9%, and cattle (Bovine spp.) killed a maximum of 4%. Pocket gophers caused the most reduction in height growth. The combination of factors caused excessive damage and mortality at all study locations, completely destroying one plantation.

Black bear (Ursus americanus) feeding on coastal redwood (Sequoia sempervirens) has been documented for several years. Quantitative analysis of the feeding damage has not been done. Feeding damage was analyzed on six belt transects in two drainages of the Smith River, Del Norte County, California. Bears are selecting trees of specific d.b.h. classes and not feeding on the size class most abundant. Damage estimates are presented for number of trees per hectare and percentage of stands that are impacted by bear feeding. A proposed approach to bear management is presented with emphasis on a multi-management approach.

In India, as in other countries, problems associated with locally overabundant wildlife species have emerged as important management issues for reason of some species losing their natural habitat but adapting themselves to the man-altered habitats. Consequently, there is a clash with the interests of local people. Crop-raiding by locally overabundant wild populations of nilgai and blackbuck in Haryana is one such problem analyzed in this paper. Nilgai causes extensive damage to agricultural crops; among these, gram, wheat seedlings and moong are the most preferred ones. Blackbuck nibble mainly on young shoots of various cereal and pulse crops and the damage is much less than caused by nilgai. Possible management strategies such as culling, fencing in nilgai and black buck (enclosures or corrals), and fencing agricultural areas to minimize the problem are suggested. Chain-link fencing of a sizable Reserved Forest (RF) patch, where the animals seek daytime shelter, combined with other local protective methods in the cultivated areas of Nahar hold promise of reducing the pest animal populations. The experiment is likely to establish one approach for dealing with the specific problem in Haryana. This paper discusses agricultural crop-raiding by locally overabundant populations of nilgai (Boselaphus tragocamelus) and blackbuck (Antilope cervicapra) in several districts of Haryana and the possible management strategies that can limit or reduce the conflict. Based on these strategies, a management experiment is being conducted in one of the districts, namely, Nahar, and its results are presented in this paper.

Over the last 30 years the wild hog population control program at Great Smokey Mountains National Park has experienced steady growth. The evolution has been relatively slow, and it was not until the latter part of the 1980s that sufficient funds were available to make a serious attempt at control measures. Over the years, the research program has focused on the biology of the wild hog; its reproductive rate; feeding and movement patterns; and its impact on the fauna, flora, and soils of the park. In addition, a major project was conducted to evaluate attractants and baits to increase the trapping success rate in the park. Finally, a population model has been developed to guide management as to the resources necessary to control the population at a satisfactory level. Based on lessons learned, the overall program is reviewed and recommendations are made for a more efficient and effective control program for the 1990s.

Information concerning vertebrate pests of beekeeping was gathered from state and provincial apiary inspectors through a questionnaire. Forty-eight states and 9 provinces responded. Additional pest information has been assembled from published articles. Bears represent the major vertebrate pest based on severity of damage to colonies. Total estimated losses reported amounted to $623,000 annually. Loss estimates for the various pest species are probably grossly underestimated because many states with problems could not or did not provide loss estimates. Skunks and house mice represent the next most important species from a damage point of view, with annual damage averaging $423,050 and $100,450, respectively. Skunk and house mouse damage, although less severe than that of bears, is far more frequent and widespread. The principal method of damage prevention is the use of electric fencing for bears while trapping is the most used method for control of skunks. Exclusion is considered the best means of resolving house mouse problems. These and a variety of minor vertebrate pests are discussed along with methods or techniques used for their prevention and/or control.

One hundred dogs were placed with sheep producers in Idaho, Oregon, Washington, and Wyoming during summer 1987 through summer 1988 as part of the APHIS-ADC livestock guarding dog program. Mortality as of February 1990 from culling and accidents is 39% and was evenly split between the first and second year of life. The 60 dogs currently working were rated as follows: 78% good, 12% fair, and 10% poor. All dogs rated good or fair were judged to have reduced predation or helped to keep predation minimized. Success of the dogs was breed-related but did not differ between pasture and rangeland sheep operations. About 50% of the producers who participated in the program either have purchased or plan to purchase additional guarding dogs.

In recent years, wildlife agencies in California have concluded that predators are limiting factors to the recovery of several endangered species, namely the San Joaquin kit fox (Vulpes macrotis mutica) , California least tern (Sterna antillarum browni), and desert tortoise (Xerobates agassizii). As a result, separate control programs for the protection of these species have been undertaken by U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Animal Damage Control (ADC) in cooperation with State and Federal agencies. Aspects of control activities of avian and/or mammalian predators of each project are discussed.

Competing concerns between conservation and sheep-growing interests in South Australia over problems associated with the naturalised dog, Canis familiaris dingo, prompted the development of a policy for the management of this subspecies. The background to the development of this policy is outlined. The policy provides for a compromise between the need to protect the livestock industry while ensuring the continued survival of the dingo as a wildlife species.

The coyote is highly adaptable in exploiting man's livestock production systems and, indeed, thrives in such situations. Recent research by the Denver Wildlife Research Center has drawn upon earlier studies to focus effort on priority needs of the U.S. Department of Agriculture's (USDA) cooperative Animal Damage Control (ADC) program. Substantial improvements have been made in some control methods and several new methods or effective modifications have become available for use by ADC and by producers. Additional developments have occurred in improving chemical delivery systems and in understanding the ecological requirements for effective control programs. With the substantial investments being made by USDA in test facilities and personnel to meet new regulatory requirements, prospects for the development and registration of new control methods and materials have greatly improved.

This paper will discuss strides taken to limit or eliminate use of the leghold trap and will explore recent trends in the animal rights movement's attack on fur and traps. A current legislative effort in Ohio, which seeks to protect wearers of fur and other animal products, as well as retailers, will be examined. Finally, the outlook as to what the future holds for the anti-trap debate and what we must do as responsible conservationists is discussed.

Seven types of breakaway snares were evaluated for breaking strength and variability using a universal testing machine. Maximum tension before breakage for individual snares ranged from 142 to 486 pounds. Sheet metal locks which ripped out, and S-hooks which straightened, provided the least variable results. Coyotes (Canis latrans), mule deer (Odocoileus hemionus), domestic calves, and lambs were tested to determine the tension loads they applied to snares. Differences in tension toads among coyotes and nontarget species should allow for the development of snares that will consistently hold coyotes and release most larger nontarget animals.

The use of dogs and calls to take coyotes (Canis latrans) around dens and resting areas has been used by the U.S. Department of Agriculture's Cooperative Animal Damage Control program for many years. This technique, when properly employed, is highly selective, humane, and very effective. In more remote, inaccessible areas it is one of the most cost-effective control methods currently available. Current and future public sentiment, as expressed in Legislative mandate, may oblige ADC to depend on methods perceived as more humane and selective. Dogs may become a more important control tool in the not-so-distant future. This technique and its applications are described.

Lamb predation in Patagonia, Argentina, is considered by ranchers as the cause of one of their greatest losses and limits sheep production. Patagonian red fox (Dusicyon culpaeus) is the main predator and the magnitude of the problem reflects its distribution and abundance. Since 1979, the Bariloche Experimental Station of the Instituto Nacional de Technologia Agropecuaria (INTA) has performed 8 studies, totaling 1,717 lamb necropsies, with the purpose of determining the relative importance of predation and other causes of lamb mortality. This paper analyzes the causes of lamb mortality, with special reference to red fox and carnivorous bird predation. Red fox predation pattern is also discussed, based on the analysis of 157 cases of red fox kills.

Efficacy of Compound 1080 LP Collars was studied under pen and field conditions. Coyotes poisoned themselves by attacking collared sheep and biting the collars. In 54 pen tests where 1 or 2 captive coyotes had opportunity to attack 1 collared lamb, 41 lambs were attacked and 26 collars were punctured. Of 25 different coyotes offered lambs with collars containing 5 or 10 mg sodium fluoroacetate (FAC)/ml, 23 coyotes attacked and 21 died after collars were punctured in their first (n = 17), second (n = 3), or fifth (n = 1) test. For 11 captive coyotes that punctured rubber collars, the average time to death was 217 min (range 115 to 436 min). Collars were placed on approximately 3 percent of the sheep on 4 Idaho and 7 Montana sheep ranches. Coyotes attacked 67 uncollared and 68 collared sheep, punctured 32 collars, and may have punctured 2 other collars that were not found. Documented rates of collar puncture were 48% for all attacks on collared sheep and 64% for neck-throat attacks. Eight collars were punctured on fences, thorns or brush. All coyotes that punctured collars probably died, but only 3 dead coyotes were found. Adverse impacts on humans, domestic animals, and nontarget wildlife were not seen. The LP Collar is a safe, effective, and selective technique for removing coyotes that attack sheep.

With U.S. Environmental Protection Agency's approval of certification and training of sodium monofluoroacetate (Compound 1080) Livestock Protection Collar applicators by the Texas Department of Agriculture in April 1988, use of collars by ranchers was made possible. This paper presents data from 1988 and 1989 on use of Livestock Protection Collars to protect domestic sheep and goats subject to coyote (Canis latrans) predation. Information concerning coyote puncture of collars, loss of collars to other factors, and targeting strategies used by ranchers are discussed. Success of collar use is compared to other predator control methods used by ranchers.

Tracerite®, the chemical marker used in M-44 cyanide capsules, contains cadmium which the Environmental Protection Agency identified as an inert ingredient of toxicological concern. An alternative nontoxic marker was identified and tested. In a weathering test, capsules with Day-Glo® performed as well as those containing Tracerite, and presence of potassium chloride in the capsules did not improve capsule function. Day-Glo was further tested by allowing captive coyotes to discharge M-44s containing sodium cyanide and various colors of Day-Glo. Twelve of 13 coyotes that died or were euthanized soon after recovering from sublethal doses had obvious marks in their mouths for 4 to 5 weeks. On the basis of these tests, the registered formulation for M-44 capsules was changed; Tracerite and KCl were deleted and Day-Glo Blaze Orange was added.

Seasonal responses of captive coyotes (Canis latrans) to 9 chemical attractants (W-U lure, TMAD, SFE, FAS, CFA, artificial smoked fish flavor, artificial beef liver flavor, yeast autolysate and decanoic acid) were evaluated. Twenty-six additional attractants were tested only during the summer. W-U lure and FAS produced the greatest total response times from coyotes during all seasons of the year. FAS and smoked fish flavor evoked the most lick-chew-bite and pulling behaviors during the summer and have potential for improving the performance of M-44 devices in warm weather.

From several centers of domestication, cats and dogs have become the near-ubiquitous companion of man. Their dependence on man is such that when abandoned in a rural environment most succumb to malnutrition in combination with predation, diseases, parasites, and exposure. Where not subject to predation and where native or introduced prey is adequate, some survive to form feral populations. This applies on oceanic islands, in Australia and New Zealand. Elsewhere, as far as is known today, requirements for survival are met with in parts of the U.S. and Europe only, in remote wilderness areas in the case of dogs, and more widespread, with a tendency to fall back on surplus and waste products of man during hard times in the wild, in the case of cats. Where vermin populations, such as those of rabbits, rats and mice are dense, cats provide inadequate control; they can be useful in keeping small vermin populations small. Away from oceanic islands and desert areas, where their impact on native animals can be disastrous, this makes them sufficiently useful for damage to wildlife (notably to lizards, small marsupials and some birds) to be outweighed, without providing a clear-cut case for a need for control of either roaming, stray or feral cats in rural areas. On the other hand, dogs are potentially destructive animals, whether roaming, stray, or feral; they demand strict control.

We examined the feeding behavior of red-winged blackbirds (Agelaius phoeniceus) and European starlings (Sturnus vulgaris) on ears of corn (Zea mays) artificially infested with corn earworms (Helicoverpa zea). In 30-minute aviary tests, redwings and starlings directed 39 to 79% more feeding responses to ears of corn with worms than to ears without worms but they damaged the same proportion of ears with and without worms. In 3-hour aviary tests and a field evaluation, birds damaged more ears with worms than without worms. In spite of more feeding responses directed to ears with worms, the overall damage (number of kernels eaten by birds) was similar in both groups of ears in aviary tests. Our findings indicate that earworms can influence feeding behavior by redwings and starlings on ears of corn. The results generally support the hypothesis that by reducing insect populations in cornfields, one can make the fields less attractive to birds. Also, because redwings and starlings actively sought earworms in corn ears, these abundant birds have the potential for reducing populations of these insect pests in cornfields.

Bird damage to early-ripening Florida blueberries was estimated to be approximately 17% in 1988 (2 sites) and ranged from 17% to 75% in 1989 (3 sites) when a late winter freeze severely reduced expected yield. Monetary loss due to bird damage in 1989 may have exceeded $4500/ac at one site. In Florida, birds appear to have a significant impact on the early-season fresh market blueberry industry. The problem is likely to worsen as the planting of high-value, early-ripening varieties spreads to other parts of the state and ripening times overlap with wintering frugivorous birds.

Bird deaths resulting from toxic materials in containment ponds are causing authorities to insist that action be taken to eliminate this hazard to avian wildlife. Bird control at containment pond sites is achieved by two well-known but poorly understood aversion techniques: hazing systems (sound/visual) and stretch wire. The limiting condition of either approach is that resident birds rapidly habituate while some migrating species are totally unaffected. Consequently, one must be able to accept degrees of control with an understanding of the behavior of the species involved. Birdproofing is achieved by covering an entire pond with bird net. This presentation discusses several aspects of bird netting including selection of net, with consideration of UV degradation, weather conditions and species, design of support systems, installation procedures, attachment techniques, abrasion limitations, and a brief summary of hanging and stretch-wire techniques.

Compound DRC-1339 is a restricted-use, slow-acting avicide that is registered to control a number of avian pests. It is unique because of its selective high toxicity to most pest birds, low-to-moderate toxicity to most mammals and predatory birds, and lack of known secondary hazards when used on baits. The most widely known product containing DRC-1339 is Purina Mills' Starlicide Complete®, a pelleted bait used to control blackbirds and starlings in feedlots. Other DRC-1339 registrations are held by the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (USDA/APHIS), for the use of nonpelletized baits at feedlots and for the control of gulls in or near their nesting colonies. Over 20 State Special Local Need 24(c) registrations have also been issued to APHIS for special DRC-1339 uses. To consolidate these registrations, APHIS has submitted data to amend its feedlot registration for blackbirds and starlings, and applied for three registrations for control of 1) raven and crow depredations on livestock and for wildlife protection, 2) pigeons in and around structures, and 3) blackbirds, starlings, and crows at preroosting staging areas. Because most of the submitted data were collected in the 1960s and 1970s, none of it was produced under the Environmental Protection Agency's (EPA) Good Laboratory Practices (GLP) regulations; therefore, new data will probably be needed to support these registrations. Future data needs and procedures for collecting valid information for DRC-1339 are suggested.

The use of trained falcons and hawks for dispersing pest birds has been mainly limited to airports in Europe and, to a lesser extent, in North America to prevent bird/aircraft strikes. The peregrine falcon (Falco peregrinus) and the goshawk (Accipiter gentilis) are the raptors used most often. These trained birds can effectively disperse gulls (Larus spp.) and a variety of other pest bird species, although other bird-scaring methods are often equally or more effective and economical. Because of the scarcity of trained raptors and handlers, their use is limited to special situations such as airports where the incidence of bird strikes is potentially high and all possible measures must be taken to assure aircraft safety.

One technique for repelling or excluding birds is to stretch wires, monofilament lines, or nylon strings across sites needing protection. Wires or lines spaced at various intervals and in various configurations have successfully repelled birds such as ring-billed (Larus delawarensis) and/or herring (L. argentatus) gulls, and brant (Branta bernicla bernicla) from reservoirs, sanitary landfills, fish hatcheries, nesting areas, public places, or farm fields. Black thread has been suggested for repelling small birds such as sparrows (unspecified) from garden seedlings and bullfinches (unspecified) from fruit trees. Recent observations in New Mexico indicated that monofilament lines spaced at 30-cm (1-ft) intervals repelled house sparrows (Passer domesticus) and other birds from various feeding sites and barn swallows (Hirundo rustica) from nesting sites. Experiments in Nebraska have tested size (1.8-, 5.4-, and 9-kg test), color (clear and fluorescent golden), orientation (north-south, east-west, horizontal, vertical) and/or spacing (30 and 60 cm) of monofilament lines in a grape vineyard and at feeding stations. Results of food consumption and bird count data indicate that all treatments repelled house sparrows. Although the reasons lines repel certain birds is not fully understood, it appears that they have probable applications for excluding or repelling certain terrestrial as well as aquatic species.

The bushfowl (Francolinus bicalcaratus bicalcaratus L.) is a major avian pest on planted maize seeds. Maize seeds coloured green and normal white seeds were planted at different depths of 2.5 cm, 5.0 cm, 7.5 cm, 10.0 cm, 12.5 cm, and 15.0 cm in three different trials between 1987 and 1988. The effect of planting depth was highly significant. Damage occurring to seeds planted at a depth of 2.5 cm was significantly higher than all the other depths, even though there was not significant damage among the other depths.

At 3 sites in Chambers County, Texas, the estimated sprout loss in 1-ac plots sown with clay-coated rice seed averaged 17.0% compared to 36.5% in adjacent 1-ac control plots. In one field, bird use of the control plot was 14 times that of the treated plot. Average feeding rates of red-winged blackbirds (Agelaius phoeniceus) were 1.5 seeds/min and 8.4 seeds/min in the treated and control plots, respectively. Roadside counts of territorial male redwings and evening flightline counts of birds going to roost indicated a depredating population consisting mainly of nonbreeding, roosting birds early in April with increasing proportions of breeding birds as the rice-planting season progressed. The results of this study are consistent with previous laboratory findings and with predictions from foraging theory. Further development and field testing of the seed coating will be required before the technique becomes generally available as a method for reducing bird damage to sprouted rice.

Roosting behavior is common to most avian pests of agriculture. Movements from highly aggregated distributions in roosts to highly dispersed distributions on foraging grounds determine pattern and severity of avian pest problems. This research seeks an understanding of bow roosting behavior influences the dispersion of avian agricultural pests and the damage they cause. My focus is on why birds form communal roosts and how communal roosting influences the selection of foraging sites. I document patterns of roosting behavior in European starlings (Sturnus vulgaris) through population level studies, followed by analysis of individual behavior using radio telemetry. Starlings maintain long-term fidelity (up to 130 days) to the same diurnal activity center (DAC), while using a variety of roosting sites at night. DACs tend to be at the center of the distribution of roosting sites used by individual birds. These and other results contradict expectations based on the most widely held explanations for roosting behavior and have led us to a new interpretation based on an association between large roosts and high-quality feeding sites (e.g., agricultural fields). Examination of previous attempts to manage avian pest problems in light of these new findings helps explain some earlier successes and failures, and may also promote development of new more efficient approaches to avian pest problems.

Bird repellents that are effective have tended to be toxic, while those that are relatively nontoxic have tended to be ineffective. There is a need for repellents that work well and safely. Interest has focused on the natural chemical defenses used by plants to defend themselves from herbivores. Preferences of bullfinches in orchards for different pear cultivars were correlated with biochemical differences between cultivars. A class of plant secondary compounds has been isolated and shown to be physiologically active against bullfinch and pigeon gut enzymes, and also to deter feeding in the laboratory. The physiological and biochemical mechanisms responsible for their repellency are under investigation.

From 1988 through early 1990 alpha-chloralose (A-C) was successfully used in the United States to immobilize and remove 70 Canada Geese (Branta canadensis), 315 mallard, domestic and hybrid ducks (Anas platyrhynchos), and 348 coots (Fulica americana) from 17 commercial and residential sites including golf courses, pools, and ponds. Field trials and baiting techniques with bread and corn are described. The optimum dose of A-C for geese, ducks, and coots, using orally administered bread and corn baits, was about 20-30 mg/kg. We are currently pursuing registration of A-C as a bird control chemical with the U.S. Food and Drug Administration.

A 2.2-ha cedar and mixed deciduous tree woodlot in Crawford, Mississippi, harboring 330,000 blackbirds (Icterinae) and European starlings (Sturnus vulgaris) was aerially sprayed by helicopter the night of 1 March 1989 with 1050 I. of a CPT-avicide formulation at a rate of 49 kg CPT/ha. Most mortality occurred within 36 h of treatment. Mortality in the roost was 3% of the pretreatment population. No reliable technique to estimate out-of-roost mortality was identified. Pilot misapplication and probable CPT volatilization of the spray formulation contributed to the low mortality. Only 1 of 37 radiotagged blackbirds using the roost the night of the spray was verified as a CPT-related mortality. Pre- and post-treatment numbers of hawks and owls in and near the roost did not differ (P > 0.05). Dead nontarget animals found in and near the roost included 10 cardinals (Richmondena cardinalis), 1 robin (Turdus migratorius), and 1 least shrew (Cryptotis parva). Additional research is needed to develop methodologies for evaluating the efficacy of slow-acting toxicants.

From 30 August to 18 September 1985, sunflower and corn mixed baits (75% sunflower meats and 25% cracked corn) treated with 1.50% CAT, (N-(3-chloro-4-methylphenyl) acetamide) were evaluated for reducing blackbird populations near Churchs Ferry, North Dakota. Baits were applied on baiting lanes in sunflower fields with an electric seeder mounted on an all-terrain cycle. Three noncommercial (decoy) sunflower fields were baited with CAT-treated baits diluted 1:9 with similar mixture of untreated bait at a rate of 50 lbs/lane acre (9.3 total treated acres). Based on total bait consumption, the estimate of blackbirds killed by the CAT treatment ranged from 13,266 to 30,650. The total amount of CAT-treated mixed bait consumed was 62.1 pounds. The predominant species causing damage in the test fields was the red-winged blackbird (Agelaius phoeniceus). Overall, redwings constituted an average of 73% of all birds observed in test fields, yellow-headed blackbirds (Xanthocephalus xanthocephalus) 23%, and common grackles (Quiscalus quiscula) 4%. Peak number of blackbirds feeding in test fields during observation periods varied from 2,250 to 10,635. Peak roost counts for roosts near test fields ranged from 60,000 to 90,000 blackbirds. Baits treated with an acutely toxic pesticide were evaluated as part of the bait mix and singly on sunflower rows as a toxic-marker. Birds and small mammals did not become immobilized and die close to ingestion sites. These results precluded the use of this toxic marker baits for estimating the number of birds accepting CAT baits. This technique does not appear promising as a technique for reducing local populations and associated sunflower loss.

New Zealand horticulturists are experiencing increasing damage to a variety of crops from a number of introduced bird species. With the advent of the increasing problem there is a need for carefully planned control operations most of which, by necessity, will be carried out by the growers themselves. This means that a variety of baits and toxins is currently being evaluated for control purposes. Growers are being trained in the use of those toxins as well as how to get more effective use from a range of bird-scare devices. Control agencies continue to carry out control of certain bird species and monitor bird damage where possible.