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Open Access Publications from the University of California


The concept of the Vertebrate Pest Conference originated in early 1960 from discussions among representatives of the University of California; the California Dept. of Fish & Game; the California Dept. of Agriculture; the California Dept. of Public Health; and the Branch of Predator and Rodent Control, Bureau of Sport Fisheries and Wildlife, U.S. Fish &  Wildlife Service.  The original participants recognized that few published documents on vertebrate pest control were available, as such information was typically contained within in-house reports of the various agencies that were largely unavailable and unable to be cited.  Dr. Walter E. "Howdy" Howard of UC realized that having a conference would permit a Proceedings to be published, in which this information could be made widely available.

To plan such a conference, the organizing group, chaired by Dr. Howard, became the Vertebrate Pest Control Technical Committee, which arranged and hosted the first "Vertebrate Pest Control Conference" held in Sacramento on February 6 & 7, 1962.  The planning committee formally became an incorporated non-profit entity in 1975, and the Vertebrate Pest Conference is now held in late winter or early spring every two years.  It is the most widely-recognized conference of its kind worldwide.

Detailed histories of the development of this Conference are found in these publications:

Marsh, Rex E.  2008.  A History of the Vertebrate Pest Conference.  Proc. Vertebr. Pest Conf. 23:310-326.

Gorenzel, W. Paul.  2004.  Opening Remarks - A Retrospective Look at the Vertebrate Pest Conference.  Proc. Vertebr. Pest Conf. 21:1-2.

Howard, Walter E.  1982.  Twentieth Anniversary of Vertebrate Pest Conferences in California.  Proc. Vertebr. Pest Conf. 10:235-236.

Howard, Walter E.  1962.  Opening Remarks – Vertebrate Pest Control.  Proc. Vertebr. Pest Conf. 1:1-7.


Opening comments - Eighth Vertebrate Pest Conference - and the stability of vertebrate populations in man-modified habitats

In addition to welcoming Conference participants, the author expresses his philosophy of the need for vertebrate pest control activities. Too few people understand that a highly stable animal-plant-soil equilibrium exists where man has not markedly altered the environment. In temperate regions, the balance of nature in natural habitats is little affected even when a large number of individuals of any one or several species of vertebrates are removed by man. The naturally evolved species that are present have acquired great resilience to offset various climatic and other catastrophes. In contrast, the type of habitat modification done by homeowners, farmers, and the like nearly always causes some vertebrates to become pests. Some conservationists, through protectionist zeal founded on ignorance of the population dynamics of vertebrates in altered environments, indirectly force many farmers to practice an undesirable form of biological control of vertebrate pests--clean farming. The farmers cannot afford to keep hedge rows and riparian vegetation because they will foster serious pest problems unless some other control is practiced. At this Conference the speakers will illustrate how they are seeking the most ecologically desirable protection of mankind's food, fiber, and other resources, including wildlife in general. All of the papers will shed light on the role that vertebrate pest control is playing in managing modified environments in perpetuity in a healthy manner.

Vertebrate pest control, where from here?

The legal and regulatory problems confronting the vertebrate pest control profession have mushroomed in recent years. The causes, the groups responsible and a suggested action plan for meeting the problem is outlined.

World bird damage problems

There is a lack of information on bird-caused economic losses on a worldwide basis. Some estimates are available for specific problems in the United States, Canada, and parts of Oceania and Europe, but loss estimates are almost totally lacking in Latin America, Asia, and Africa. To justify development of control programs, it is desirable that reliable data on losses be obtained. Such data are helpful at all levels of decision-making about bird control, from research to implementation. Bird damage situations throughout the world are similar, involving many of the same crops and genera of birds. This report summarizes major damage problems reported for each continent in tabular form. Agricultural problems are emphasized; other examples are given including bird hazard to aircraft, predation by undesirable species, urban and rural roost problems, birds as carriers or transmitters of disease, and beneficial aspects of some species. Control methods are not reviewed.

Chopped cabbage baits for ground squirrel control in Nevada

Effectiveness of four cabbage baits was tested on Belding (Spermophilus beldingi) or Townsend (S. townsendi) ground squirrels. Ground squirrel activity reduction and number of above ground deaths/ 100 lb. bait applied were as follows: 0.00625% sodium monofluoroacetate - 94 1/2%, 2-1/3; 0.29% strychnine alkaloid - 86%, 17; 0.19% strychnine alkaloid - 73 1/2%, 10. A 0.8% zinc phosphide bait was not well accepted; activity was reduced 39%. Two cottontail rabbits (Sylvilagus nuttalli) and one badger (Taxidea taxus) were found dead in treatment fields after treatment.

The changing rodent pest fauna in Egypt

The most serious known rodent pests in agricultural irrigated land are: Rattus rattus, Arvicanthis niloticus and Acomys sp. Occasionally there are rodent outbreaks in agricultural plantations. The changing agro-ecosystem in the present and future agricultural plantations is expected to affect the status of the following potential rodent pest species: Spalax ehrenbergi aegyptiacus, Nesokia indica, Jaculus orientalis, and Gerbillus gerbillus gerbillus. Basic studies are needed to quantify damage including water loss, which is caused by rodents, forecast of rodent outbreaks, and integrated control of rodents in agricultural projects.

Recent developments in bird damage control chemicals

A number of actions are under way which could reduce or severely restrict the availability of chemicals presently available for controlling bird damage. The current status of 17 federally registered chemicals, representing approximately 57 products, is discussed with regard to registration, re-registration, or de-registration actions that are pending. The developmental status of a number of new chemicals or new uses for existing chemicals is also discussed, along with an appraisal of the effects of current federal registration requirements on the eventual availability of these compounds.

Bird damage research at the University of California, Davis

The University of California, Davis, starling research program was broadened in 1976 to encompass agricultural pest birds in general. Under new direction there were a number of applied problems studied. The effects of feeding cattle only between 1600 hours and 0800 hours on cattle weight gain was studied with results indicating slower weight gains and lower meat quality when compared to cattle fed ad lib. Feed component selection by starlings (Sturnus vulgaris) was also studied finding that a starling selected diet contains a higher percentage of the high protein components than present in a commercially prepared dairy feed ration fed to them. References are given to papers on a damage assessment technique for grapes, a field test of methiocarb as an avian repellent to protect figs, and a field test using Avitrol treated seed to control house finches (Carpodacus mexicanus). An overview of continuing research activities and a status report on the bird damage specialist position is discussed.

Control of the multimammate rat, Mastomys natalensis (A. Smith) in the irrigated fields of the Republic of Burundi

Irrigated cultivations have been developed in Burundi with the aid of the European Fund for Development. Three major rodent species are considered pests, but one of them is far more important and can survive flooding: Mastomys natalensis, the multimammate rat. The biological cycle of the species is well identified, with peak populations generally in the July-October period. A first attempt to prevent the damages consisted of slight changes in the timing of some cultivations. The second step was to find a rodenticide and a bait that could have practical use in that country. Corn paraffin blocks poisoned with chlorophacinone appeared to be convenient. 80-95% control is obtained with 2-3 kg. bait per hectare.

Population modeling as aid to rodent control in the field

Forecasting the damages by voles on plant crops depends on a good forecast of vole population density. Biological work in Vendee from 1959 til 1968 has furnished the fundamentals of a population model. Further work on the relationship between breeding and climate enabled us to set up a practical forecasting model. This is applied by the Plant Protection Service, and the damage prevention system consists of a test trapping in winter, a population forecasting in early March, and, if necessary, poisoning in March-April. Generalization of the system is in progress.

Rid-A-Bird perches to control bird damage

Rid-A-Bird wick perches, using 9.4% endrin or 11% fenthion, may be used on a variety of structures for control of house sparrows, starlings, and pigeons. Installations take advantage of a bird's propensity to perch briefly before feeding or entering roost or nesting structures. Applications may be made to a variety of structures but are restricted from food storage or preparation areas. Additional toxicity and use research is needed.

Improvements in the use of 4-aminopyridine for protecting agricultural crops from birds

In 1976 and 1977, studies to improve the use of 4-aminopyridine (4-AP), a chemical frightening agent for protecting crops from blackbird damage, were conducted in sunflower in North Dakota, corn in Ohio, grain sorghum in Kansas, and sprouting rice in Arkansas and Texas. Because of the high vulnerability of sunflower, much of the effort was concentrated in this crop, despite the 1976 federal registration of a 4-aminopyridine product, Avitrol® FC Corn Chops-99S, in 14 midwestern states. Hand baiting the perimeter of fields appeared effective in protecting sunflowers from damage by three species of blackbirds, but was ineffective in protecting grain sorghum being damaged by cowbirds. A 1:33 dilution ratio of 4-AP was more effective than the registered 1:99 dilution ratio in protecting field corn. A concerted effort to bait the most vulnerable sunflower fields in a 7-township area with small tractors on baiting lanes did not provide the degree of protection anticipated. In this study about 38% of radio-equipped blackbirds frightened from ripening sunflower fields fed next in equally vulnerable sunflower fields. Good to excellent results were obtained in initial trials with 4-AP for protecting sprouting rice fields. Fair success was obtained using 4-AP formulations for protecting corn and sunflowers from parakeet damage in South America and rice and millet from damage by weavers in Africa.

Management of blackbird and starling winter roost problems in Kentucky and Tennessee

Blackbirds and starlings in winter roosts create conflict problems in five major categories: 1) Public Health, 2) Agricultural Crop, 3) Wildlife Competition, 4) Structural, 5) Safety. After identification of problems created by an individual roost and roost site, problems are solved by one or a combination of seven methods: 1) No Action, 2) Move the Roost, 3) Alteration of Agricultural Practices, 4) Bird Proofing, 5) Move Birds from Feeding or Loafing Site, 6) Population Reduction at Feedlots, 7) Population Reduction of Roosts.

County programs for vertebrate pest control in California

Vertebrate pest control is an important function which has been performed for many years by County Agricultural Commissioners. Since 1917, control materials have been prepared and distributed to assist farmers in the control of rodents and pest animals. Our authority for these programs comes from the California Food and Agricultural Code. It explains why this aspect of pest control is conducted by Agricultural Commissioners.

Vertebrate pest control in urban/suburban areas

Urban/suburban vertebrate pest control problems present unique challenges because of the people-afflicted environment in which they occur. People are a major consideration in effective urban/ suburban vertebrate pest control because of their emotions and changing values. Those responsible for today's vertebrate pest control must anticipate and consider this element of increasing importance and use it to their advantage rather than let it become a liability.

A public information program on predator damage control

A public information and education program was developed in Oregon to defuse a controversy between environmentalists and livestock growers over management of predator damage control. Emphasis was placed on involving special interest and leadership/influential groups in the program and participation was high. Attempts were made to involve the "general public" but response to solicitation and participation were low. Participating groups thought the program was of high value and expressed the need for additional information. Attitudes and beliefs of the special interest groups were changed little by the program, but constructive communications between the groups increased and the controversy dwindled. A 17-month survey of livestock losses to predation was conducted as part of the program. Loss rates of livestock to predation (3.9 percent of lambs, 1.6 percent of ewes, and 0.7 percent of calves) agreed with those of studies in surrounding states and provided another perspective for objective evaluation of the predator control controversy by participating groups.

Granivorous birds in sunflower crops

Bird communities visiting and causing damage to sunflower crops were studied in western Switzerland. The greenfinch is the main pest species. A population study of that species was carried out in Changins, near Nyon, and crop protection techniques, including an ultrasonic device, were tested.

Biology, damage and control of the edible dormouse (Glis glis L.) in central Italy

The remarkable increase in the number of colonies of edible dormouse (Glis glis L.) registered in the litoranean industrial cultivations of Pinus pinea L. in northern Tuscany over the last ten years and the grave damage to the production of pine-seeds consequent on it has created the necessity of studying systems which may reduce the dormouse menace. Going on what has previously been discovered about the habits of the species in this particular habitat, three different methods of control were experimented: direct capture in their nests, which were in this case cavities in the tree trunks which woodpeckers' activities had made accessible to the dormice; capture by means of specially built artificial nests; distribution of bait composed of pine seeds poisoned with chlorophacinone. All three systems - the first two of which can be conveniently used together - are worth further investigation and experiment, considering their results, to examine their individual advantages.

Control of the house mouse (Mus musculus L.) in the Netherlands

Rodent control in the Netherlands is carried out by local authorities, extermination companies or the owners of infested premises. The control of the house mouse, especially in food-handling establishments, is a problem that has existed for some years. Testing in the laboratory indicates a warfarin resistance although the application of new rodenticides like bromadiolone, calciferol and difenacoum has given good results. A "manual" for the control of suspected warfarin resistant house mice is given.

Electromagnetic repellers: Fact or fiction?

The effectiveness of devices that supposedly repel a large number of invertebrate and vertebrate animals by emitting oscillating electromagnetic impulses is investigated. While scientific support that electromagnetic forces affect biological systems exists, these data are based on animals confined under higher intensity fields than are seemingly produced by commercial units. A number of instances of field use of the devices is discussed. These indicate little objective support for the units.

Ground squirrel damage and control in Montana

The Columbian ground squirrel (Spermophilus columbianus), Richardson ground squirrel (Spermophilus richardsoni), and blacktail prairie dog (Cynomys ludovicianus) cause millions of dollars of loss to Montana agriculture each year. Montana's ground squirrel and prairie dog control programs are based upon local organization and operation with technical assistance being provided by the Montana Department of Livestock Vertebrate Pest Control Bureau. The results of field research programs using zinc phosphide, Compound 1080 and strychnine grain baits to control these species are reported.

Control of ground squirrels in California using anticoagulant treated baits

Anticoagulant treated grain baits have been used to control vertebrate pest depredations in California for over 30 years. The use of anticoagulant treated baits has increased 7 times in the past 7 years; the majority for the use of ground squirrel, Spermophilus spp., control. Since 1968-69, an average of 1,747,828 net over 5,700,919 gross acres per year has been treated for ground squirrel control. Current use patterns for ground squirrel control with anticoagulant treated baits include: (1) Repeated spot baitings, and (2) exposure of bait in bait boxes. Experimental work and many years of operational field use have proven that anticoagulant treated baits have a place in effectively suppressing ground squirrel populations in localized areas, with little hazard to non-target animals. However, these baits have not proven to be a practical substitute for current techniques of suppressing ground squirrel populations over large areas, such as in rangeland situations.

Pheromones: Their potential for ground squirrel control

Olfactory communication appears to be an important aspect of the biology of most ground squirrels. Several scent-producing glands have been described as having scent-marking behavior. Although the adaptive significance of these glands has not been determined, possible functions are discussed. The potential of using pheromones in an integrated ground squirrel management program is discussed.

Muskrat control in the Netherlands

Muskrats were introduced into Europe and have now spread over this part of the world. Their success as a colonizing species is discussed, as well as the problems they create in a man-made environment. Due to their successfulness, a strict control program has been changed to a management program in order to keep numbers below the level at which intolerable damage occurs.

Rodents as agricultural pests in Mexico National Rodent Campaign

Since 1973, through the Ministry of Agriculture and Water Resources, the Mexican Government has established a general campaign against the most important groups of vertebrate pests, which cause severe damage to growing crops, stored products and mechanical damage to agricultural and irrigation schemes. To achieve information on this subject, presently the main office of the program is engaged on several activities such as the evaluation of the damage, trapping, species involved, research on population structure (densities and fluctuations to prevent sudden increase of rodent population), sex proportion, pregnancy (number of embryos), bait formulation, distribution methods, etc. Sigmodon spp., Oryzomys spp., Peromyscus sp., Rattus spp., Mus sp., Microtus spp. and several members of the Geomyidae have been found to be of a great importance under field conditions.

Vacor, a new rodenticide: Its success in the field

Since VACOR® was first introduced to the market as a fast-acting rodenticide in 1975, it has been sold successfully throughout the United States. The VACOR line is sold over-the-counter as a ready-to-use bait for rats and mice. The DLP-787™ rodenticide line was introduced to the market for sale to professional users only. This line includes both bait and mouse tracking products. It has been well accepted by professional users even though DLP-787 is offered only as ready-to-use products. New products of the same type will be available for commercial introduction in 1978. This paper discusses the successful market entry of VACOR and DLP-787, their field use against commensal rodents, and the new products now on the horizon.

Rodenticidal activity of bromadiolone--a new anticoagulant

Bromadiolone, a new anticoagulant rodenticide, has been evaluated against laboratory rats and mice. Kill of both species was excellent, even when bromadiolone was offered for only one day in the presence of alternative food. Effectiveness against homozygous warfarin resistant rats was also demonstrated. Limited field trials on farms showed that after baiting for seven days with bromadiolone, warfarin resistant rat populations were substantially reduced although subsequent re-infestation occurred. Longer or continuous periods of baiting with bromadiolone would almost certainly prevent population increase, but government restrictions on the amount of bait approved for the trials did not allow this to be demonstrated.

Brodifacoum (Talon™ rodenticide), a novel concept

Brodifacoum, a new rodenticide, is described. This anticoagulant is shown to be of exceptional potency and capable of controlling resistant rodents as well as several non-commensal species. Results demonstrate that, in contrast to first generation anticoagulants, a bait concentration of only 50 ppm is adequate to give control and in only a single feeding for most species. In common with other anticoagulants, vitamin K1 is an effective antidote. In contrast with other acute rodenticides, symptoms are delayed and no bait shyness is observed. The results of laboratory and field trials from many parts of the world are summarized and comparisons of efficacy and specificity with other rodenticides are made. In all cases, brodifacoum is shown to be an exceptional rodenticide, the single feeding action of which offers novel rodent control applications.

Vexar plastic netting to reduce pocket gopher depredation of conifer seedlings

In 1976, we began a comprehensive evaluation of "Vexar" seedling protectors as a means of reducing damage to conifer seedlings by pocket gophers (Thomomys spp.). The protectors are cylinders of plastic netting that gradually decompose in sunlight. The evaluation is being conducted on four national forests in three western states. Three conifer species, lodgepole pine (Pinus contorta), ponderosa pine (P. ponderosa), and Shasta red fir (Abies magnifica var. shastensis), are under study. After two growing seasons, gophers have caused only 5 percent mortality among "Vexar"-enclosed seedlings compared to 20 percent mortality among unprotected seedlings. In addition, stocking and heights of protected seedlings are better than those of unprotected seedlings. Problems associated with the use of "Vexar" included compression of the protectors by snow, breakage of the plastic during subfreezing temperatures, and protrusion of seedling terminals through mesh openings; however, these problems have been minor thus far. Information on long-term effectiveness and cost efficiency is still needed before we can recommend operational use of "Vexar" protectors for pocket gopher damage control.

Establishing native forbs to reduce black-tailed deer browsing damage to Douglas-fir

Principal methods being used to alleviate browsing damage to Douglas-fir (Pseudotsuga menziesii) seedlings by black-tailed deer (Odocoileus hemionus columbianus) in the Pacific Northwest are animal repellents applied to foliage and plastic mesh cylinders around individual seedlings. As an alternate method, we demonstrated that prompt establishment of highly palatable native forbs reduced summer browsing on planted seedlings to the point that black-tailed deer were no longer a factor limiting Douglas-fir regeneration. We believe that establishing native forbs is a sound ecological approach to deer-reforestation problems; furthermore, it should have wide utility because it integrates forest- and wildlife-management objectives by promoting prompt regeneration of conifers and enhancing wildlife habitat.

Anticoagulant baiting for jackrabbit control

The jackrabbit, Lepus californicus, is properly called a hare rather than a rabbit, because the young are born fully furred and with eyes open. Hares differ from rabbits in anatomy and in the lack of burrowing, although individual hares often have a more or less regular retreat or "form" at the base of a bush or clump of grass. Jackrabbits rely upon speed and dodging to escape enemies. They live chiefly in open places, seldom inhabiting dense brush or woods. Black-tailed hares or jackrabbits are classed as game mammals by the California Fish and Game Code, but when found to be injuring growing crops or other property may be taken at anytime or in any manner by the owner or tenant of the premises. They also may be taken by employees of the Department of Food and Agriculture or by county employees when acting in their official capacities pursuant to the provisions of the California Food and Agriculture Code pertaining to pests. In recent years large roving populations of jackrabbits on airports have created serious problems to approaching aircraft. One such problem occurred at the Hayward Municipal Airport in Alameda County when jackrabbits caused a traffic hazard to approaching aircraft. The problem was compounded by domestic dogs chasing rabbits across the runways and dead rabbits being fed upon by scavenger birds such as gulls and turkey vultures.

Agricultural pest destruction movement in New Zealand

New Zealand could be regarded as an acclimatization laboratory, i.e., the consequence of a wide range of animal introductions in the period 1840-1907. Species introduced ranged from camels to hedgehogs, ostriches to sky larks. Fortunately, many failed to survive. The majority of these liberations were made by Acclimatization Societies or private individuals, often with Government approval and protection. The most damaging species were several species of deer, rabbits, Australian opossums, goats, pigs, tahr, wallabies, and chamois. Pastoral land development in the early days usually consisted of firing large tracts of indigenous forest and native grassland and this practice assisted the dispersion of some animals, particularly the rabbit. The impact of these animals was to upset the natural stability of habitat and damage soil and water values. Organizations constituted by Government with the responsibility of conducting control have in recent years made dramatic progress in reducing some animal populations to tolerable levels. This has only been achieved by positive policy changes over the years, plus the development and utilization of more effective control techniques, especially in the field of poisoning. Discussion of current species of concern includes the European rabbit, brush-tailed possum, rook, and wallabies. Control methods are briefly summarized.

Rodent population control for public health and safety

Rodent populations - particularly those that live in close proximity to man - constitute a perennial and often severe threat to man's health as reservoirs and often as direct sources of infection for a wide variety of viral, rickettsial, and bacterial disease producing agents. The following will discuss the place of rodent population reduction for the control of plague, a bacterial disease of rodents transmitted by fleas endemic in the western United States.

Influences on the science of animal damage control

The author discusses the complexity of animal damage control science and its research, methods development, and control applications. It is not the point here to discourse on the individual methodology used in animal damage control research. The discussion is to point out that many researchers, wildlife managers, bureaucrats, or advocates fail to understand the situation in the science of animal damage control and its attendant problems that need resolution. Scientists should not forget that animal damage control is a science and an art. It is devoted to the recognition, analysis, and evaluation of environmental resource damage problems caused by wild and feral animals. Those problems are extremely complex and cannot be left to advocates and revelationists. Given the state-of-the art in the science of animal damage control, the only way to resolve this problem is to change the philosophy on future research, methods development, and application.

Wildlife as vectors in diseases: approaches to solving these problems in the United Kingdom

Interest in wildlife diseases and their importance to man and his livestock has increased in the United Kingdom during the past decade. Reasons for this are given and particular reference made to the single occurrence of rabies outside quarantine in Britain, in 1969 (the first since 1922), and to the links between bovine tuberculosis in badgers and in cattle.

Vertebrate control chemicals: Current status of registrations, rebuttable presumptions against registrations, and effects on users

Pesticides federally registered for use against vertebrate pests are listed and discussed. Although the number of registered pesticides appears substantial, most are chemicals of questionable utility (e.g., naphthalene, mineral oil, bone oil, and sulfur dioxide), and are not considered as viable alternatives to more typical pesticides. The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) as amended is described in relation to vertebrate pesticides. Reregistration of all currently registered pesticide products, as now required by FIFRA, is discussed. Through cancellation and suspension procedures, known as Rebuttable Presumption Against Registration (RPAR), the Act authorizes the removal from the market of registered products purported to cause unreasonable adverse effects. The author discusses pesticide labelling, application certification, Experimental Use Permits (EUPs), and emergency use and state restrictions. Regarding vertebrate pest control chemicals, the author views some of the inter-related positive and negative impacts of amended FIFRA and as enforced by the EPA as follows: 1. Land managers will be forced to absorb more losses caused by vertebrate pests due to the lack of chemical tools and higher costs of fewer pesticides. 2. Higher costs are inevitable; the cost of bringing a new chemical on line has risen from $1 million in 1956 to $8 - $10 million. 3. Research & development and registration time-frames of new chemicals have doubled, leaving much less time to achieve a profit under 17-year patent protection. 4. The probability of finding new vertebrate pest chemicals is extremely low. 5. A trend toward usage of less toxic or persistent products is in progress, even if effectiveness and low cost are sacrificed. 6. The recognized need for highly selective and safer products presents a cost and registration quandary. The author concludes that the pendulum of public emotion regarding pesticides has swung from blind commitment to all forms of progress to another extreme. The pendulum has not yet swung back to a position many of us consider reasonable.

Present and historical bobcat population trends in New Mexico and the West

Bobcat (Lynx rufus) populations throughout the West have reportedly decreased from the high levels of the early sixties. This decrease is also reflected in the annual New Mexico bobcat take of the U.S. Fish and Wildlife Service when based on a bobcat trapped per man-year of effort relationship from 1916 through 1976. Bobcat populations in New Mexico were comparably low from 1916 through 1948. In 1949 through 1950 populations began to increase to triple their highest pre-1948 levels by the late fifties. New Mexico bobcat populations began to decrease in the early sixties to present levels typical before 1948. The same New Mexico bobcat population trends reflected by this data are also reflected throughout the West in the combined bobcat take totals for the U.S. Fish and Wildlife Service in the western states. The bobcat population decrease from the early 1960's was not caused by habitat loss, fur trapping, or predator control. The unprecedented bobcat increase in the early fifties was in direct response to the general reduction of coyote numbers throughout the West by the use of sodium monofluoroacetate (1080) as a coyote control tool. After several years, coyotes began to increase their numbers, and bobcat numbers responded inversely by a decrease of their numbers down to present lower levels. Bobcat, skunk, fox, and badger numbers have all responded inversely to that of coyote numbers due to the coyote's role as an efficient competitor and predator upon these other carnivores.

Reproductive inhibitors for coyote population control: developments and current status

Coyote depreciation often causes severe losses of livestock and wildlife in many areas. The use of toxicants is banned for coyote control in the United States necessitating the consideration of alternative methods of control of these predators. This review deals with a class of possible alternatives for population control (reproductive inhibitors) and the conditions associated with selection and application of reproductive inhibitors to the target species.

Coyotes, sheep and lithium chloride

The use of LiCl-treated baits and carcasses has been advocated as a means of controlling coyote predation on sheep through a process known as "aversive conditioning or taste aversion." While some investigators have made well publicized claims of damage reduction through the use of LiCl on sheep ranges, other researchers have experienced difficulty establishing prey aversion in captive coyotes. The conflicting results suggest a need for extensive, carefully controlled research in both pen and field situations before valid conclusions can be reached regarding aversive conditioning as a depredations control method.

The toxic sheep collar for control of sheep-killing coyotes: A progress report

The toxic sheep collar is the most selective method known for killing coyotes that prey on domestic sheep. The concept dates back to the early 1900's and has been studied at the Denver Wildlife Research Center (DWRC) since 1974. Field tests with sodium cyanide (NaCN) in 1975 were unsuccessful due to repellent properties of the toxicant and to the apparent reluctance of coyotes to attack tethered lambs wearing bulky collars. Coyotes attacked one or more tethered, collared lambs in 7 of the 19 test pastures. In all, 14 collared lambs were attacked. Eight of the collars were punctured but no dead coyotes were recovered. A smaller collar containing diphacinone was field tested in 1976. The diphacinone-filled collars were readily accepted by coyotes and lethal to them, but the slow action (5-16 days between dosing and death) of diphacinone made it difficult to assess the effectiveness of these collars under field conditions. Target flocks containing 1 to 12 collared lambs plus uncollared ewes were placed in 15 fenced pastures from which the larger ranch flocks had been removed after repeated coyote predation. One or more collared lambs were attacked in 11 of the 15 tests. An unknown number of coyotes were killed, and in most tests the subsequent incidence of predation was lower than that before the test. Captive coyotes continued to kill sheep for 4 or 5 days after they received a lethal dose of diphacinone; therefore a faster-acting toxicant is needed. This research has shown that problem coyotes can be killed with toxic collars, but further studies are needed to determine the feasibility of this approach compared with traditional means of control. In most tests to date the frequency of coyote predation has been too low and too irregular to permit effective use of the collar; target flocks were in the field for an average of 10 days before being attacked. The known disadvantages of the method include the need to sacrifice live lambs, the human hazards associated with the use of toxicants under field conditions, and the costs of managing target flocks and other sheep in the problem areas.

Sheep depredation by golden eagles in Montana

A limited study on two ranches near Dillon, Montana, near the end of the lambing season in 1974 revealed that 44 domestic lambs were killed by golden eagles (Aquila chrysaetos). This was 76 percent of all deaths recorded during the short study. Using an average docking percent of 90 (based on years before severe eagle problems developed), the 76 percent eagle predation, and the 1974 docking percentages, the ranchers estimated an eagle kill of 1,092 lambs valued at about $38,000. The U.S. Fish and Wildlife Service live-trapped and removed 249 golden eagles from the ranches during the next three springs. During 1975, when 145 eagles were removed, docking percentages were even lower than in 1974, and the ranchers estimated a loss of $48,000. During 6 hours on one ranch in 1975, I found 15 fresh eagle kills. Less severe eagle problems occurred during 1976 and 1977, and the docking percentages improved. The effect of the trapping program on predation could not be evaluated. Lamb losses were greatest during the years of greatest trapping success. Decreasing lamb losses in 1976 and 1977 may have resulted from increasing populations of jackrabbits (Lepus spp.) throughout the West. Juvenile and subadult golden eagles caused most of the predation. A decline of jackrabbits may have caused these young birds, which had no established territories, to concentrate on the lambing grounds. As numbers of sheep decline on western ranches, eagles may take a greater percentage of lambs from the remaining herds. With golden eagles totally protected, increasing predation on lambs should be expected, especially when natural prey is scarce. Because of the expense and the relative scarcity of qualified personnel, the trapping and moving of depredating eagles is not a practical operational procedure. Non-lethal methods of eagle management show little promise for alleviating lamb losses. Experiments should be conducted combining scare tactics, including shooting near the birds, with limited killing for reinforcement. Illegal control may endanger juvenile bald eagles (Haliaetus leucocephalus) and result in the killing of many golden eagles if ranchers are not assured of aid when a serious depredation problem occurs.

Changing status of mountain lion in California and livestock depredation problems

The California Department of Fish and Game studied depredation by mountain lions on livestock from 1971 through 1977 to determine the scope of the problem. Information was needed on the physical characteristics of a stock killer, the frequency and trend of predation, the livestock types preyed upon, and the geographic distribution of incidents. Department of Fish and Game verified 134 incidents of mountain lion predation on livestock which occurred between April 1971 and December 1977. Forty-five mountain lions (28 males and 17 females) were killed on depredation during this time. Approximately 42 percent of the predation incidents involved sheep, 22 percent goats and 16 percent cattle, with horses, pigs, poultry and pets composing most of the remaining prey. California's south coast region from Santa Clara to Ventura County reported 44 percent of the predation incidents, 28 percent from the Sierra Nevada, 20 percent from the north coast from Napa and Sonoma counties to Humboldt County and nearly 8 percent from southern California. There does not appear to be a stock-killer profile of common sex, age or health factors. Present depredation policy appears adequate to handle the problem, but efficiency could be increased by coordinating incident verification investigations and available depredation resources, such as U.S. Fish and Wildlife Service and county predator control agents.

The black-breasted lark (Melanocorypha bimaculata), a pest of sorghum in Butana region, Gezira Province, Sudan

Attempts were made to investigate and account for some aspects of the present status of the black-breasted lark (Melanocorypha bimaculata) as a pest of sorghum in one of the rain-fed semi-desert areas of the Sudan. Also some observations were conducted to understand the behavior and the feeding habits of the pest in relation to crop damage phenology. Problems encountered in the application of some control techniques were discussed and evaluated in order to suggest sound control strategy.

Some problems concerning the control of bird damage in south-western Nigeria

The problems of controlling bird damage, especially to crops, may be both social and practical. The practical problems are subject to environmental and ecological factors. The social problems relate to lack of adequate biological knowledge of the pest species, lack of confidence between farmers and researchers, persistent government red tapes, and human feelings. Damage is often as a result of feeding and nesting activities. Control measures include both prevention of contact between birds and crops by erection of barriers, use of chemical repellents and scaring devices, and attempted reduction in numbers of pest species, by shooting and trapping. None of the control methods is satisfactory. Local farmers have resulted to the use of 'juju' -- a mystified composition of no scientific qualification yet surrounded by lots of taboos and to which huge successes have been ascribed. It is pertinent in our stage of development to encourage and continue detailed biological research of the local fauna.

Warfarin baits bagging to control the population of cotton rats in field crops in Sinaloa, Mexico

Tests were conducted using 0.05% warfarin baits which were put into polietilinized paper bags with corn oil as attractants, in order to control cotton rats (Sigmodon hispidus major) through-out 4,000 ha. of crops in the Sinaloa State. Both the effectiveness of the warfarin bait and the security and efficiency of the handling of the polietilinized paper bags was demonstrated. Furthermore, the tests showed that there were economic advantages in using the warfarin baits instead of the zinc phosphide baits; to the extent of a 46.67% saving in the control expenses.

Damages caused by cotton rat, Sigmodon hispidus zanjonensis, on sugar cane in San Pedrosula, Honduras

Technical assistance was given to Compañía Azucarera Hondureña, S.A. (Agro-Industrial Co.), Honduras, Central America, to determine if a campaign against noxious rodents to agriculture crops was needed. Several trappings were carried out at different places using snap traps to determine the population structure of rodents associated with the crop, and live traps to determine the index or density of the Sigmodon hispidus rat population, which was identified as being responsible for the damage to sugarcane. Results were 43.24% adult males, 14.86% young males, 31.41% adult females, and 10.47% young females. Of the adult females captured, 54.83% were pregnant with an average of 3 to 4 embryos per rat. A control demonstration combat was carried out at one of the experimental stations with a bait prepared with 2% zinc phosphide in a place where it had been previously determined there was a population of 39 rats per hectare. After such control, the population was reduced to 18 rats per hectare, which represents an efficiency of 53.85%. An evaluation of damages was also measured at different places to determine the degree of loss caused by the rats, which proved to be 22.79% damage. The size of the sample was estimated in 3 samples per hectare, with a level of confidence of 95%.

Biological control of conifer seed damage by the deer mouse (Peromyscus maniculatus)

This paper describes the development of a biological technique that successfully controls conifer seed damage by the deer mouse. Eleven experiments have been conducted on three study areas at the University of British Columbia Research Forest, Maple Ridge, B.C. Populations of deer mice have been monitored in all experiments with data from 56,000 trap nights. The technique involves a mixture of conifer seed (Douglas fir) with sunflower seed and oats which is uniformly distributed on logged areas in the late winter-early spring. Survival of conifer seed with these alternate foods was excellent, compared with control Douglas fir by itself, for an 8-week period during this time of year. Populations of seed-eating birds and chipmunks are not present on clearcut areas from late October to early April. In addition, deer mice are at their lowest density during the spring. Thus, the use of alternate foods with Douglas fir seed in a direct-seeding operation at the appropriate time of year will result in successful regeneration of cutover forest lands.

Aversive conditioning tests of black bears in beeyards failed

This study evaluated the effectiveness of emetic compounds (lithium chloride and cupric sulfate) in honey baits as a technique for preventing black bear damage in fenced beeyards. LiCl and CuSO4 in honey baits did not reduce black bear damage at beeyards. Our experience indicates that LiCl is not a suitable emetic for producing taste aversions in free-ranging black bears.

The potential of compound U-12171 as an avian repellent

Tests of the effectiveness (primarily reduced plant damage) of U-12171 to repel linnets from, or reduce the amount of feeding damage on, Gem hybrid broccoli suggest that: 1) concentrations above 1.50 lb./acre deterred avian depredations whereas lower concentrations did not; 2) the "hop-scotch" feeding pattern of linnet groups may have contributed to repellency since high concentrations in one area may act as a barrier to other areas; and 3) U-12171 efficiency may be markedly affected by chemical coverage of the plant, the number of applications made, and application timing relative to crop maturity.