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Open Access Publications from the University of California


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

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

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

Salmon, Terrell P. 2012. VPC: Fifty Years of Progress? Proc. Vertebr. Pest Conf. 25:3-6.

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

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

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

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


Changing times for animal damage control

At present, the USDA’s Animal and Plant Health Inspection Service (APHIS) is in the process of taking over the national animal damage control program from the U.S. Fish & Wildlife Service. I discuss the history of the federal animal damage control program with the U.S. Department of Agriculture beginning in the late 1800s. Once USDA assumes full control of the present program, the areas of emphasis will be cooperative operational control, research, and informational and educational efforts. For the first time, the program will have a Secretary’s advisory committee on ADC. An interdepartmental policy committee chaired by APHIS will involve other USDA agencies: Forest Service, Extension Service, Economic Research Service, Agricultural Research Service, and Cooperative State Research Service. Details of future efforts in research, and in information and education, are discussed.

The status of bromadiolone in the United States

The anticoagulant rodenticide bromadiolone is used throughout the U.S. under a number of trade names. An expanded research program is underway within Chempar to examine the use of bromadiolone in commensal and field rodent control. Data are presented herein on the toxicology, metabolism, secondary hazards, efficacy, and formulation developments with bromadiolone. A new Maki 0.001% liquid bait is being tested and excellent control results obtained against Norway rats (Rattus norvegicus), roof rats (R. rattus), and house mice (Mus musculus). New Maki paraffin blocks containing 50 ppm bromadiolone have been developed and are soon to be on the market. Bromadiolone biodegradability in the field and in animal tissues offers promise for expanded label claims for use in urban and field situations.

A review of brodifacoum efficacy in the U.S. and worldwide

In this extensive review, we note that brodifacoum has been successfully evaluated against most small mammal pests around the world, and in a variety of both commensal and agricultural situations. Brodifacoum offers reduced rodenticide requirements to lower costs and hazard, and makes new baiting strategies, such as pulsed baiting, practical for large-scale use. Broad spectrum activity enables effective control with mixed-species infestations and against those normally tolerant of other anticoagulants, such as house mice. Useful against warfarin-resistant commensal rodents, brodifacoum gives effective control in urban and other situations where first-generation anticoagulants have previously been extensively used. It has the same mode of action and antidote (vitamin K) as other anticoagulants, providing the advantages of delayed action. We include exhaustive appendices of brodifacoum’s toxicity to a wide diversity of rodents worldwide, as well as listings of previous published research on this new compound.

Recent research on red squill as a rodenticide

Red squill has been used in rodent control for several hundred years but in the United States its use has decreased since the 1950s. However, there is now a recognized need for rodenticides with different kinds of toxic activity. Red squill is being investigated as an acute rodenticide and an economic crop for the southwestern states. Clones from a prior USDA collection have been assayed by high-performance liquid chromatography and selections are being propagated in California and Arizona. The major toxicant, scilliroside, is relatively fast acting, causing convulsions and death to rats and mice. This glycoside is also strongly emetic to humans, cats and dogs, affording a safety factor uncommon to high-toxicity rodenticides. Our chemical, processing, agronomic, and toxicological studies are a technical basis for further developing this potentially superior rodenticide.

An urban roof rat control program in Orange County, California

A program to control roof rats (Rattus rattus) has been conducted by the Orange County (CA) Vector Control District since 1975. Located in southern California just south of Los Angeles, urbanization takes up about ½ the total area of the county, and it is mainly a semi-desert situation with <15 inches which is used by rats as harborage and s a food source. The roof rat is a difficult animal to control. Our program is basically a complaint/response program; we have tried neighborhood surveys and inspections and found them not to be cost-effective. When we receive a service request, a technician visits the property to inspect for rat sign, harborage, food sources, and entrances into structures. The technician provides the landowner with written recommendations and an educational pamphlet. With the landowner’s permission, rodenticide bait, if needed, will be placed on the property by the technician; however, it is the owner’s responsibility control rodents within a residence himself or by hiring a pest control operator. The program emphasizes public education, environmental management, and chemical control. The program also conducts ectoparasite and disease surveillance; however, if fleas are rare or absent on roof rats, then in most cases there is little justification for rat control to be done by a public agency.

An integrated pest management approach to roof rat control in oceanfront riprap, Ventura County, California

During the summer months of 1979, public agencies in Ventura County, CA, received complaints which pointed to a rodent infestation of campground areas along the north coastal strip. Investigations revealed a widespread infestation of oceanfront riprap by roof rats (Rattus rattus). Visual surveillance, trapping, baiting and population-estimating techniques and results are described and discussed. Implementation of integrated pest management practices resulted in the reduction of rat populations to a no-complaint level and provided a framework for a long-term maintenance program.

Results of eight years' examination of the habitats of residual urban Norway rat populations after eradication

In Budapest (population 2 million), 33 out of 100 buildings were rat-infested in the early seventies. Thus general deratization was decreed to cover the whole of the city in 1971 to 1972. As a result of the global eradication method applied, the rate of rat-infested premises could be reduced below 0.5% annually. After control the sparsely occurring rats could freely choose any of the habitats released for settling. The habitats of Budapest most preferred by Norway rats are presented after a wide-ranging investigation carried out over 8 years. Our examination data support and in some cases reveal the requirements of Norway rats living in Central European large cities as regards to the environment as well as their ethological features. This knowledge may help in improving deratization and especially maintenance operations, thus increasing the efficiency of the fight against rats.

New potential diagnostic methods for identifying anticoagulant rodenticide poisoning in dogs and other nontarget animals

Use of the enzyme-linked immunosorbent assay (ELISA) to detect anticoagulant compounds in non-target animals (companion animals, livestock, and wildlife) is described. Such immunoassays are sensitive to the presence of anticoagulants in the ng/mL range, which is parts per billion (ppb) of biological material. This assay strategy is explained, as is progress to date in detecting diphacinone and chlorophacinone.

An evaluation of the acute oral toxicity of brodifacoum to birds

Single acute doses of the rodenticide brodifacoum were administered orally to 13 species of birds which are at risk from accidental poisoning during rabbit or possum control operations. Median lethal dose values from less than 1 to more than 20 mg/kg were obtained for some species. Gulls and Canada geese appear to be particularly susceptible. Several species, particularly the gulls, waxeyes, sparrows, mallard ducks and harrier hawks, seem to be vulnerable to lead poisoning.

Intoxication of domestic and wild animals by anticoagulant rodenticides--a synthesis of data from the French National Veterinary Antipoison Center

During the period from 1980 to 1985, the laboratory of toxicological analysis associated with the National Veterinary Antipoison Center received 1,343 samples for research of anticoagulant rodenticide (e.g., 14.1% of total samples): 79% concerned animals, 31% baits. Six compounds marketed in France were investigated (warfarin, chlorophacinone, bromadiolone, difenacoum, coumachlore, coumatetralyl). In two-thirds of the samples, none of these substances could be found. Warfarin was by far the most incriminated rodenticide (23.1%), and dogs represented the most affected species (65.7%). However, its occurrence decreases regularly. The other compounds were found with a very low frequency (1 to 3%). In 70% of the cases, baits were prepared with criminal intention of killing animals other than rodents.

The complexities at the interface among domestic/wild rodents, fleas, pets, and man in urban plague ecology in Los Angeles County, California

Bubonic plague was first found in Los Angeles County in 1908. The largest epidemic of pneumonic plague in the United States occurred in the county in 1924, and the last cases of plague associated with domestic rodents in the United States occurred here in 1925. Sporadic plague activity was recorded from 1925 to 1975. Since 1975, plague has been found annually and is now endemic in the San Gabriel Mountains and the interface, that area where suburban encroachment intermingles with wilderness areas along the southern edge of these mountains. Within these two areas, plague is amplified and is a risk to humans when it occurs in the California ground squirrel, Spermophilus beecheyi. This rodent has been implicated directly in two human cases and is now peridomestic throughout most of the interface area. A domestic cat was implicated with another case; the role of domestic pets in plague ecology is discussed. Although large populations of Rattus rattus exist within the interface, they currently play no role in plague ecology due to the virtual absence of fleas. The oriental rat flea, however, is seasonally very abundant in Rattus norvegicus living adjacent to the interface area and poses an alarming potential for epidemics if plague ever was introduced into this host population. The plague surveillance program in Los Angeles County centers on an active intelligence network to report signs of plague activity and on the combined use of serologies taken from wild carnivores and S. beecheyi. Early detection by these means plus active flea and ground squirrel suppression programs have been implemented to reduce plague activity and prevent human cases.

An integrated approach to bubonic plague control in a southwestern plague focus

Plague is widespread among rodents and their fleas in the western United States, but most human cases occur in several definable, ecologically unique, and geographically limited high risk areas in the Southwest and Pacific Coast states. Control strategies to prevent human cases in high risk areas must vary from one epizootic focus to another, depending on such basic ecological factors as rodent/flea species involved; their distribution, abundance, seasonality, and relationship with the plague organism; climatic factors that affect transmission; the lifestyles of human residents; and others. This paper briefly summarizes preliminary results of a long-term program to define human risk and develop effective surveillance and control measures against plague in a north-central New Mexico plague focus.

Potential of vegetation management for ground squirrel control

Manipulation or alteration of habitat vegetation is used frequently with integrated pest management of certain vertebrate pest species. However, it has been less than satisfactory with ground squirrel species in many situations. Special plantings of tall grasses and broadleaf species were experimentally explored in an effort to make levee habitat less suitable for the California ground squirrel in the Sacramento Valley. The experimental plantings failed to achieve that objective for a variety of apparent or suspected reasons and, in fact, in some grass plots the number of ground squirrels increased over what was present prior to planting. Other problems associated with these experimental plantings, including aggressive tendencies of some species, are discussed.

Bait preference field study for the California ground squirrel

A bait preference field study of the California ground squirrel (Spermophilus beecheyi beecheyi) was performed involving the comparison of the following untreated bait formulations fed ad lib: oat groats, Ramik Green, and ZP Rodent Ag Bait. The study was performed on rangeland at California Polytechnic State University, San Luis Obispo, California, from March 11, 1984, to September 15, 1984. Poor bait quality problems occurred in the early period of the study (March 11 to May 17), resulting in poor acceptance of both Ramik and Ag Bait. A descriptive analysis of this period is discussed. The statistical analysis of relative bait consumption (June 3 to September 15) determined a significant difference between the consumption of oat groats versus Ramik and Ag Bait; no significant difference between Ramik and Ag Bait; the acceptance of all three baits was good; and the use of any of the three would result in control of the ground squirrels. There was a strong correlation between overall bait consumption and the ground squirrels observed.

Population dynamics and expansion rates of black-tailed prairie dogs

The purpose of this review is to describe population dynamics and annual rates of increase of black-tailed prairie dogs (Cynomys ludovicianus) and to determine annual expansion rates of uncontrolled populations. Their reproductive characteristics, including social behavior are examined as they relate to these factors. In this analysis, the first step is to determine the average number of male and female prairie dogs of breeding age that are present at each burrow system before and after the reproductive cycle. From this determination the total number of prairie dogs is determined, based on the average density of active burrows for a specific geographic area. Then specific natality and mortality rates are determined to establish the total population. These data are essential to management decisions regarding expansion of prairie dog colonies and related control programs.

The effectiveness of strychnine laced alfalfa on pocket gopher activity in Diamond Valley, Nevada

The Townsend pocket gopher (Thomomys townsendii) poses a serious economic threat to alfalfa production in Diamond Valley, Nevada. Many control methods have been practiced with only limited or seasonal success. Application of strychnine-treated alfalfa hay has been an effective control method; however, the relationship between strychnine concentration and pocket gopher kill has not been examined. This study was conducted to evaluate the effectiveness of three concentrations (0.5%, 1.0% and 1.7%) of strychnine-treated alfalfa hay baits. The three strychnine levels and untreated control were replicated three times on twelve 0.8-ha (2.0-ac) plots. Plots were located on a 6-year-old stand of sprinkler-irrigated alfalfa. Pocket gopher activity, (mound count census method), was monitored pre- and post-treatment to estimate bait effectiveness. Data were evaluated by regression analysis of variance. Average percent changes in gopher activity were +24%, -40%, -78%, and -69% for treatments 0%, 0.5%, 1.0%, and 1.7%, respectively. There was a significant (P<0.01) negative effect of strychnine concentration on pocket gopher activity.

The house mouse in poultry operations: pest significance and a novel baiting strategy for its control

Enclosed and insulated commercial poultry buildings provide ideal habitat for supporting unusually large populations of the house mouse (Mus musculus L . ). Mice cause damage to various structural and operational components of poultry facilities; thus, they are of economic significance as well as general nuisances. Effective mouse control programs in poultry operations are often difficult. complicated, time consuming, and inefficient due to various environmental and operational factors intrinsic to commercial poultry facilities. The significance of the house mouse as an economic pest in poultry operations is discussed via the results of a rodent control survey of 161 commercial poultry operations in Indiana. Survey data are presented concerning mouse problem incidence and severity, mouse damage, and mouse control tools and methods operators judged most successful. A research project aimed at developing more cost-effective and efficient methods of controlling mice in commercial poultry operations was begun at Purdue in 1985. The project involves the development of a novel rodenticide baiting strategy utilizing customized PVC anticoagulant bait stations, second-generation anticoagulant baits, and a "time-pulse" baiting strategy. Preliminary field trials of this baiting technique have produced population reductions of 78.8% and 74.4% in two poultry houses following a one "pass" application rate. Research addressing additional application rates is continuing as well as investigations into modifications of this baiting strategy for application in other types of poultry and livestock operations.

Wildlife damage in conservation tillage agriculture: A new challenge

Conservation-tillage farming systems have changed agriculture and brought new challenges to the wildlife damage field. Associated minor problems may result from the presence of rattlesnakes (Crotalus viridis) or badgers (Taxidea taxus), but sprout-pulling damage by birds has not been reported. Rodents dig and consume newly planted corn. At least 14 small mammal species have been captured in no-tillage cornfields, some species throughout fields and others primarily at edges. Deer mice (Peromyscus maniculatus) generally have been the most abundant, comprising 71 to 93% of total captures. Small mammal populations in no-tillage fields are generally no higher than in conventionally tilled fields, but they may be more diverse, and possibly more stable. Rodent damage to newly-planted corn is variable among fields and years but is at times substantial, possibly resulting in annual losses of up to $16 million in Nebraska. Six rodent species have been implicated in the damage problem but the overall amount of damage caused by each species is unknown. Currently, there are no satisfactory control methods. A new zinc phosphide grain bait is being developed; other potential controls include cultural methods, alternate feeding, and repellents. Benefits of small mammals such as their consumption of crop-damaging cutworms should be considered in control decisions. Wildlife damage problems in conservation-tillage systems, particularly rodent problems, challenge further research to better quantify associated impacts and to develop appropriate control measures.

Anticoagulant translocation and plant residue studies in crops

Three types of assessment techniques explore the possible environmental hazards of two anticoagulant compounds currently used for rodent control. In the first, rheological methodologies were used to assess the ability of pelletized baits to withstand precipitation. From these data, objective information was developed to assist agricultural producers to select a proper bait for a specific climatic period. Bioanalytical evaluations of chlorophacinone indicated that the compound decomposes when exposed to ultraviolet light into four nontoxic elements. Hence, if translocation were to occur, the elements--not the parent compound--would be the likely candidates. Finally, radioactive (14C) bromadiolone was tested for translocatability. From the preliminary data developed to the date of this report, little, if any, translocation occurs.

Advances in the integrated control of the European rabbit in South Australia

In South Australia, success in control of the European rabbit has been based on an understanding of rabbit biology and behaviour. Drastic population reduction is obtained by use of Compound 1080. This method is much more effective when carried out during midsummer to late autumn. At this time, territorial boundaries are relaxed and the young have been weaned and are feeding aboveground. To ensure that the greatest number of rabbits can receive a lethal dose, it is necessary to pre-feed the population with unpoisoned bait over a period of 8 to 10 days. Oat grain has been chosen as the preferred bait material because of its acceptability and to minimize possible off-target effects. As warrens are an essential factor in rabbit survival, warren destruction is a vital part of any effective control programme to prevent a resurgence of the population. Poisoning followed by ripping of warrens and then fumigation provided effective control in the most cost-efficient manner. Warrens can be destroyed with minimal disturbance to areas of valuable native vegetation. By promoting this system of integrated control and by explaining to landholders the biological reasons for its effectiveness, the major rabbit problems of South Australia's agricultural lands have been overcome. In addition to the improvements in farm productivity in both the short and long term, rabbit control often appears to be an essential tool in the management of native vegetation and native herbivores. In the low-rainfall parts of the state, the low productivity of the land makes it difficult to justify this system of integrated control in terms of cost-efficiency. Ripping of warrens by itself has been shown to provide reasonable control in hilly country with 250 to 300 mm of rainfall, when control takes place late in summer when rabbit numbers are low. However, biological control in the form of myxomatosis provides the most likely means of keeping rabbit numbers at a low level throughout the low-rainfall areas. European rabbit fleas from the arid parts of Spain are expected to be introduced soon to help spread myxomatosis more effectively in the arid parts of South Australia.

Specifications for wire mesh fences to exclude the European wild rabbits from crops

The sizes of hexagonal and rectangular meshes needed to exclude all age classes of rabbits (Oryctolagus cuniculus) were 31 mm and 50 x 25 mm, respectively. In an enclosure, fences 0.75 m high excluded >90% of adult rabbits, a similar percentage to that obtained using the commonly accepted height of 0.9 m. In a subsequent field experiment using fences with a mesh size of 31 mm and heights of 0.9 m and 0.75 m, the numbers of rabbits seen on protected fields were reduced by about 80% for each height and therefore the 0.75-m-high fence was more cost-effective.

Comparison of fumigant gases used for rabbit control in Great Britain

The two most commonly used fumigant formulations, one generating hydrogen cyanide (HCN) and the other phosphine (PH3), were compared in paired field trials using the spoon-gassing technique. The two formulations were equally effective in reducing rabbit numbers seen in spotlight counts. The PH3-generating formulation was more convenient and slightly cheaper to use. Safety and humaneness aspects of the two formulations are discussed and alternative formulations (generating HCN and PH3) are considered. The potential usefulness (for rabbit control) of some other fumigant gases is briefly reviewed.

Approaches to small-holder rodent control

In spite of the clear need for rodent control at the village level, few countries have implemented effective rodent control programs directed at small-holders. Scientists tend to blame this on administrators but, in reality, many proposed programs are simply not practicable in developing countries. When small-acreage farmers have attempted to control rodents on their own, even when their neighbors do nothing, rodent damage can be achieved, but farmers may easily become discouraged by the prolonged effort involved. An alternative is to adapt control methods to the organizational constraints. Much simpler control methods are needed, which can be carried out through the coordinated efforts of large numbers of farmers. Some examples of such projects have been described earlier; here, we summarize the results of three further projects that illustrate progress towards integrated management programs.

Efficacy of a carbon monoxide gas cartridge against field rodents

Efficacy data of a gas cartridge are reported. The gas cartridge contains 50 g of potassium nitrate (27.5 g, 55%) mixed with sawdust (22.5 g, 45%). When ignited, it generates large amounts of carbon monoxide (avg. 23.46%) and carbon dioxide (avg. 26.26%). A mimic field trial was carried out on a winter day. The air temperature averaged 1.2°C, ranging from -3.3°C to +5°C. Sixteen adult albino rats were killed within 3 minutes exposure in a man-made burrow system, 200 cm long, with an inside diameter of 8 cm. Field trials were conducted in different parts of China, and there were no survivors in the 108 burrows treated. Upon excavation 144 dead rodents were recovered. The first test was carried out in Zhengding, Hebei Province. (The site was along a sunning ground where cereals are dried.) Each of 53 burrows was treated with a 50-g gas cartridge. When the burrow systems were excavated, 81 dead rodents were found: Cricetulus barabensis, 38 (46.9%); C. triton, 28 (34.6%); Mus musculus, 14 (17.3%); and Apodemus agrarius, 1 (1.2%). The second trial was carried out in a sugarcane field near a ditch in Zhangjiang, Guangdong Province. Fifty-five dead rodents were dug out of the 50 burrows treated: Rattus flavipectus, 26 (47.3%); Bandicota indica, 18 (32.7%); R. losea, 7 (12.7%); and Suncus murinus (Insectivore), 4 (7.3%). The third trial was conducted in a high mountain grassland pasture above 3500 m in Qinghae Province. Five marmot burrows were each treated with a dose of 600 g of gas cartridges per burrow. Eight dead Marmota hymalayana were found near the burrow entrance.

Field evaluation of single and multiple dose anticoagulant rodenticides in reducing rodent populations and damages in coconut plantations

Comparative efficacy of brodifacoum, bromadiolone (second-generation single-dose anticoagulant) was evaluated in a coconut crop on Minicoy Island. Pre- and post-rodent control relative levels of rodent populations and damages were recorded as indices for assessing effectiveness of different concentrations and different bait formulations of three rodenticides. The black rat, Rattus rattus (Linnaeus), constituting a new record for Minicoy Island, was the predominant rodent species infesting the coconut crop. On an average, application of brodifacoum (.005% and .002%), bromadiolone (.005% and .002%) and warfarin (0.025% ) reduced rodent populations by 74.5, 73.58, 79.1, 69.16 and 68.44% respectively, resulting in reduction of rodent damages to nuts by 74.93, 70.26, 78.24, 69.53 and 61.9% respectively. However, brodifacoum (.005% ) impregnated with rice and coconut oil controlled rodents by 86.88% with reduction in damages by 82.85% . It was followed by bromadiolone (.005%) mixed with rice and coconut oil giving 86.48 and 83.33% control of rodents and damages, respectively. Except in the case of brodifacoum (.005%), where pulse baits were more effective than ragi baits, the effectiveness of baits followed the order of rice>ragi>pulse. Similarly, coconut oil proved to be best attractant followed by groundnut oil and palm oil. Results of these field rodent control studies are compared with field/ laboratory evaluations of respective rodenticides on Rattus rattus.

Plagues of the house mouse in south eastern Australia

Plagues of the house mouse (Mus musculus) occur at irregular intervals throughout the agricultural regions of south-eastern Australia. This paper discusses these phenomena in terms of their impact on agricultural production, previous attempts to reduce damage and levels of infestation, and associated environmental implications. Consideration is also given to the accurate prediction of mouse plagues and the control strategies which need to be in place if effective management is to become a reality.

Agriculture and forest rodent problems and control in Italy

Rodent pest problems and their control in Italy are reviewed. Two rats, Rattus norvegicus and Rattus rattus, and the field mouse, Apodemus sylvaticus, are often important pests both in rural and forestry areas. Other species, such as voles, Microtus arvalis and Microtus (Pitymys) savii, in orchards and in horticulture, and Sciurus vulgaris and Myoxus (Glis) glis in forestry, sometimes represent serious problems. For each species the kind of damage and control is recorded, and additional considerations are supplied to the public and private organizations responsible for rodent control.

Rodent problems of the West Indies

The commensal rodents as we know them are an introduced species into the West Indies. They came with the first explorers from Europe and the first slaves from Africa and were spread not only in the West Indies but North and South America as well. The first record of attempts at their control was in Barbados in the 1700s when two pence was paid for each rat caught. Active control has been going on in the islands since the 1960s and 1970s with only partial success. The Pan American Health Organization is now assisting many of the governments with their problem and programs.

Rodent control in East Africa

The East African nations of Ethiopia, Somalia, Kenya, Uganda, Tanzania, Malawi, Mozambique, and Zimbabwe encompass a widely varied topography, and climate from tropical to temperate. Where soil and rainfall permit, agricultural crops are grown. For the most part, farming is of a subsistence nature being small single family plots, which make up about 90% of the farming in these nations. Large farms in Kenya and Zimbabwe are generally confined to the temperate uplands, and elsewhere there are large government agricultural schemes growing food crops like rice and sugar cane. Almost all of the nations of East Africa have chronic food shortages. The impacts of the most economically important rodent species, including the multimammate mouse, grass rat, Norway rat, roof rat, and house mouse, as well as these species biology, are summarized. A 2-year rodent control program in Somalia, funded by FAO, began in 1981 and is briefly described, as are recent rodent control projects in other East African countries. A positive outcome of these projects is that they have incorporated education for responsible national staff who in turn will train fellow workers. Long-term support for such efforts is needed.

Strychnine-salt blocks for controlling porcupines in pine forest: efficacy and hazards

Strychnine-salt blocks were evaluated for effectiveness in killing porcupines (Erethizon dorsatum) in pine forests in Oregon and California. Radio-collared porcupines were exposed to strychnine-salt bait located on trees and on the ground in covered bait stations called "cubbies." Bait blocks placed in trees and in cubbies were poorly accepted by porcupines. Only 4 of 32 marked porcupines exposed to bait were poisoned. Two died at cubbies and two died at trees. Other wildlife found poisoned at cubbies were seven unmarked porcupines, seven yellow-pine chipmunks (Tamias amoenus), five Nuttall's cottontails (Sylvilagus nuttallii), four deer mice (Peromyscus maniculatus) three golden-mantled ground squirrels (Spermophilus lateralis), and one Douglas' squirrel (Tamiasciurus douglasii). Fewer nontarget animals--two unmarked porcupines, two yellow-pine chipmunks, and one northern flying squirrel (Glaucomys sabrinus)--died at tree sets. Bioassays with caged porcupines further indicated that strychnine alkaloid is an ineffective toxicant for porcupines.

Pocket gopher damage to conifers in western forests: A historical and current perspective on the problem and its control

Pocket gophers (Thomomys spp.) damage or destroy regeneration on hundreds of thousands of acres of forestland in the western United States each year. Despite years of research, poisoning the offending animals--a technique developed around the turn of the century on agricultural land--is still the most prevalent practice for controlling damage on western forests.

Protection with Vexar cylinders from damage by meadow voles of tree and shrub seedlings in northeastern Alberta

Vast areas of land will require reclamation and reforestation following oil sands development in northeastern Alberta. Greenhouse-grown tree and shrub seedlings used in reforestation may be clipped or girdled by meadow voles, especially during periods of high population density. The impact of partial girdling, the most common form of damage, varies among species. Reduced survival rates in seedlings girdled over as little as 50% of their circumference and reduced growth rates in seedlings girdled over as little as 25% of their circumference, have been noted. Plastic mesh cylinders (tradename Vexar) have proven effective in preventing seedling damage and durable in the climatic extremes occurring in northern Alberta. Growth and survival rates of all species of protected seedlings have been at least equal to unprotected seedlings and substantially greater in some. The purchase and installation cost of Vexar cylinders is approximately 25% of the cost of growing and planting a seedling.

A five-year evaluation of the silvicultural treatments for the control of squirrel damage in Taiwan

The Formosan red-bellied tree squirrel (Callosciurus erythraeus) is a pest animal that causes serious damage to many conifer plantations in Taiwan. Poisoning has been the major means to control the damage. The feasibility of forestry control through habitat manipulation has been evaluated during the past 5 years. The objective of this study was to investigate the effects of forest-tending operations on the activity and damage by squirrels. Forest-tending conducted included weeding and thinning. Test sites were at three Japanese cedar (Cryptomeria japonica) plantations located in Chitou. The results of this study revealed that squirrel activity in the treated plots was greatly reduced. It was found that new damage done by the squirrels in treated areas was also reduced. This was particularly significant during an abnormal weather period when there was a continual rainstorm lasting for about 3 months. The treatments of weeding and thinning showed more significant effects on the reduction of squirrel activity than the reduction in the occurrence of new damages.

Why do possums survive aerial poisoning operations?

Major causes of failure of aerial poisoning operations against possums identified were: sublethal toxic loading, undersize sublethal baits, nonlearned behavioural aversion to 1080, and failure to encounter bait. Dislike of bait was not a major cause of failure. Progress has been made towards solving these problems, but failure to encounter bait remains a likely major reason for possums surviving aerial poisoning. Improvements in the aerial sowing of bait are essential if the full benefit of this progress is to be realised.

The mechanical control of bushpig, Patamochoerus porcus, in Zimbabwe

Bushpig, Potamocheorus porcus, occurring naturally in the high rainfall areas of Zimbabwe, have become a major threat to maize producers in the country. Traditional means of control including hunting have been unsuccessful in keeping the numbers to a tolerable level owing to the secretive and cunning nature of the animal. The use of poisons has been discouraged because of indiscriminate use and problems of secondary poisoning, so alternative methods of mechanical control were sought. Several methods evolved during experimentation, producing a strategy to control bushpig throughout the year.

Implications and management of feral mammals in California

"Feral" is defined. For each of the principal species of feral mammals in California, we note the broad ecological implications they have on the environment and the potential or actual management approaches being followed. The main emphasis of this paper, and all of the slides shown, was on how wild horses and burros, two controversial feral species, are managed in California and in other western states. The feral pig is about to become the number one big game animal in California, and muskrats (Ondatra zibethica (L.)), which were introduced or escaped into the Sacramento Valley--hence locally feral--are the state's number one furbearer. Except for these species, the other feral mammals are, for the most part, much less desirable.

ntegrative models of poisoning vertebrate pests

Strategies for the control of vertebrate pest are identified using mathematical models of poisoning. The models integrate aspects of foraging ecology and toxicology in a probabilistic framework. The structure, assumptions and control implications of the models are presented. Variables (control parameters) influencing the probability that a pest animal dies in a poison programme are identified and classified according to their degree of operator control. Control strategies suggested by the models are identified, and practical means of applying them are discussed. The models suggest that the probability that an animal dies is a function of 15 to 17 control parameters, of which operators have direct control over a maximum of 4: poisoned bait abundance, poison bait dispersion, the time over which poisoned bait is available, and poison concentration.

An economic threshold model for house mouse damage to insulation

Commensal rodents have become increasingly troublesome and damaging pests in insulated structures. Modern poultry and livestock confinement buildings in the Midwest often have insulated walls and ceilings. These buildings usually provide an optimum habitat for rats and mice; the rodents gnaw, tunnel through, and nest in the insulation, decreasing its insulative value. Such structures are known to be heavily damaged within a matter of months when commensal rodents have access to wall spaces and attics. We have developed an economic threshold model to help livestock producers or building managers decide when to conduct house mouse (Mus musculus) control in such situations. The model is based upon the cost of house mouse damage to commonly used types of insulation in walls, as measured in laboratory experiments. Components of the damage are 1) the cost of insulation replacement, and 2) increased heating costs due to damaged insulation. Damage costs are compared to the expense of conducting mouse control using anticoagulant rodenticides in permanent bait stations located throughout the structure. The model concludes that it is cost-effective to implement a baiting program for mouse control in nearly all insulated confinement buildings. The cost of control is usually very small when compared to the cost of potential mouse damage.

Enterprise budgets: a tool for vertebrate pest control decision making in developing countries

Semi-subsistence farms that predominate in developing countries have more complex goals than the strict profit motives of corporate farms. Small farm management decisions are commonly based on a desire to increase production while avoiding risks and reducing labor demands and operating costs. Enterprise budgets are a valuable tool for understanding diverse farming systems and farmers' decision-making processes. The preparation of enterprise budgets documents production expenses, labor requirements, and specific activities related to pest control, as well as sources of supplies and technical information. By identifying what resources are commonly used and the relative importance of farm labor, the preparation of enterprise budgets facilitates the development of appropriate rodent control techniques and effective extension programs.

An approach to the design of target-specific vertebrate pest control systems

Vertebrate pest control has the dual objectives of maximizing efficacy and minimizing nontarget hazard. The task in design is to make these objectives complementary, rather than mutually exclusive. Historically, vertebrate pest control has emphasized target control as a single objective, with nontarget impact a subsequent, secondary consideration. This sequence necessarily constrains the capacity of the design process to minimize nontarget impact. I describe a framework for the design of vertebrate pest control which is based on comparative evaluation of the socioecology of target and potential nontarget species. Using this approach, control systems are designed which focus on and exploit identified differences between target and nontarget species. This approach aids the design of control systems which optimize efficacy and nontarget impact. Further, it facilitates identification of needed research and development, specifies potential problems of nontarget impact, and enables system redesign and refinement prior to implementation. The approach is illustrated with the example of poisoning programmes for feral pig control in Australia.

Current changes to vertebrate pest management in New Zealand

Vertebrate pest control in New Zealand is changing as a result of a reduction in state funding. Monetary assistance for control programmes is being withdrawn at $0.8 million per year and currently is $5.4 million. This reduction affects several parts of the organization and the Agricultural Pests Destruction Council has initiated various programmes to rationalize control. The major effect of reducing assistance is that the landowners have to contribute more money. The necessity of blanket control of rabbits is now questioned and two investigations are underway to determine the extent of the areas where rabbit control is required and demonstrate the effects of withdrawing any form of control from certain land classes. A national recording scheme is being implemented and computerization with a common format will enable pest districts to pinpoint problems and the APDC to summarize the national scene. Changes in technology have enabled the work force involved in control to reduce from 1200 (1972) to 400 (1986) with no apparent increase in reported pest problems. These changes include increased mechanization of bait manufacture, improvements in ground-laying techniques from 4-wheel drive vehicles, motorcycles, and use of fixed-wing aircraft or helicopters. Increased reliance is placed on Rhodamine bait trials for deciding whether poisoning programmes go ahead and trials of anticoagulants for rabbit control are continuing. An Environmental Impact Report on the introduction of rabbit fleas and the virus myxomatosis was commissioned by the APDC but not submitted for audit because of public opposition, uncertainties in performance, and perceived technical problems relating to the establishment of the rabbit flea in parts of the problem areas.

Batproofing structure with birdnetting checkvalves

Denial of re-entry (batproofing) through structural modification is widely accepted as the most effective and ecologically sound method for eliminating commensal bats from structures. Such methods are clearly superior to lethal measures which have only questionable efficacy and may exacerbate bat/human interactions. However, since bats are able to enter small and obscure openings, conventional batproofing of all such openings is often not practical or economical. Further since this work must usually be done after bats have already begun roosting in a structure, the difficulty of high ladder work at night to seal exit holes can be discouraging to homeowners as well as to pest control operators. A few exclusion devices have been developed previously, but are not readily adaptable to the frequent situation where bats are using diffuse, large, and/or widely distributed exit holes. Polypropylene bird-netting has been field-tested over two seasons as a batproofing tool against little brown bats (Myotis lucifugus) and big brown bats (Eptesicus fuscus). In all cases the work was completed either before young were born or after they were able to fly. The netting is fitted as a checkvalve which allows bats to escape from a structure but prevents their re-entry; thus, the netting can be conveniently applied during daylight hours. At dusk, bats easily find their way out, do not become entangled, and are not driven indoors into the living quarters. At dawn, bats return in their typical swarming behavior, repeatedly land on the net, but are unable to find their way around or under it. Several checkvalves designs have been adapted to cover different patterns of exit holes associated with various architectural details. Specific application techniques with bird-netting checkvalves and responses of the bats are discussed in reference to overall bat management programs.

Application of a benefit:cost model to blackbird damage control in wild rice

From commercial fields near McArthur, California, we collected data on methods for controlling blackbird (Icteridae) damage to wild rice (Zizania aguatica). Using and expanding upon an economic model proposed by Dolbeer (1981), we derived economic comparisons of three control programs employing: 1. methiocarb, 2. shooting and propane exploders, and 3. all methods combined. Shooting and propane exploders used together were the most cost effective with a benefit:cost ratio of 2.16:1. Under the assumptions used in the model, methiocarb was least effective with a benefit:cost ratio of only 0.62:1. We discuss assumptions of the model and using basic initial data (cost and efficacy of control, average yield and value of the crop, anticipated damage level) illustrate a format to derive figures for the amount and value of crop to be saved at a given efficacy level, benefit:cost ratios, and net income after control.

Laboratory efficacy studies with strychnine baits on pigeons

Pigeons held under a fall and spring photoperiod-temperature regime consumed a maximum of 16.9 to 21.4 kernels of whole corn per hour with an average ranging from 7.6 to 12.4 kernels per hour. Peak consumption occurred during the first and/or next-to-last hour of the day with a secondary, but smaller, peak around noon. Corn consumption ranged from 91 to 112 kernels/bird/day and approximated daily consumption equal to 10% of an average bird's mass. The acute oral LD50 of strychnine alkaloid to pigeons was estimated to be 7.73 mg/kg (95% Confidence Interval of 6.75 to 8.85). The LD90 was 10.99 mg/kg (8.79 to 13.7) and the LD10 was 5,37 mg/kg (4.35 to 6.63). Time to death ranged from 5 to 39 minutes. Treatment of groups of 10 pigeons at 6-hour intervals beginning at 0600h with 7.73 mg/kg strychnine suggested that pigeons were more sensitive to intoxication at 1200h and 1800h than they were at 0600h. Laboratory tests of 0.2, 0.4, and 0.6% strychnine-treated whole corn bait with pigeons during the first hour of the day and at noon indicated that mortality from the 0.2% bait was insufficient for adequate control (17 to 33%). The 0.4% and 0.6% baits, however, produced acceptable mortality (48 to 71%). Pigeons killed by the 0.4% and 0.6% baits consumed from 11 to 21 kernels of corn depending upon the time of ingestion. Strychnine residues in the crop and gizzard contents of pigeons consuming 0.4% and 0.6% baits ranged from 455 ppm to 1500 ppm. Residues in birds fed the 0.4% baits were 37% that of those fed the 0.6% bait during the early morning, and 49% that of birds exposed at noon. Gizzard residues ranged from 16 ppm to 38 ppm and intestinal tissue residues ranged from 4.6 ppm to 9.2 ppm and were not correlated with treatment or treatment time. Strychnine residues in organs (heart, liver, and kidney) ranged from not detectable to 2.2 ppm and residues in muscle from 0.17 ppm to 0.56 ppm. These data indicate that a 0.4% strychnine alkaloid bait may be an effective substitute for the 0.6% bait now registered by the U.S. Fish and Wildlife Service (Pigeon Bait Poisoned Grain, Reg. No. 6704-42). The exposure of predatory and scavenger birds and mammals to potential secondary poisoning following the consumption of strychnine-treated pigeons could be reduced by 51% to 63% with the use of the 0.4% bait.

Barn owls and industry: problems and solutions

Three methods were explored to eliminate damage caused by owl pellets and fecal droppings: exclusion; trapping; and sound deterrents including abstract sound, biosonic sound, and high frequency sound. Initial successful results of various types of sound diminished with time to the point that owls adapted and ignored all sound repellents within a short period. Exclusion techniques were ineffective as owls would find ways around, through or between any non-permanent structure blocking entry through warehouse openings. Live-trapping and relocating owls was the only effective technique tested in this experimental program. Three trap methods were found effective, but trap success diminished with use of each method. Thirteen owls were trapped in one warehouse during this study using bal-chatri, goshawk and drop-net techniques. The details of each method are discussed.

Evaluating a pop-up scarecrow coupled with a propane exploder for reducing blackbird damage to ripening sunflower

A combination Purivox® Double-John carousel propane exploder and CO2 pop-up scarecrow operated in synchrony was evaluated in five ripening sunflower fields in 1981 and 1982, respectively, near Devils Lake and Westhope, North Dakota. In each field, this treatment was evaluated in an alternating off-on sequence of 5-day intervals for a period of 20 days. In 1981, devices were deployed at one unit per 8 to 10 acres and in 1982 at one unit per 4 to 6 acres. The degree of effectiveness for reducing bird damage in three of five fields that met selection criteria ranged from 71 to 87% with a mean of 78%. During the first 10-day cycle, damage on these three fields was reduced 70, 89, and 95% or a mean of 84%, while in the second cycle damage was reduced an average of 59%. In the remaining two fields in which blackbirds were well established, damage was only reduced 8 and 31% during the entire test period. This was attributed to well-established feeding patterns in the fields by large flocks of blackbirds from a nearby roost. The cost to operate one unit on 6 acres of sunflower was $14 per acre if prorated over a 10-year period (the expected unit life). Bird damage must be 18% or higher before a grower could expect a return on money invested with this device. The cost-benefit ratio in this study was 1:2.3 because damage exceeded the 18% level. Although the cost-benefits of the combination scare device indicated that for most growers in North Dakota the cost of control would exceed the dollars saved, it would be most useful in about 1.2% of the fields which annually get more than 18% damage.

Approaches to coot management in California

Coot depredations have been documented in California since 1886, and shooting has been relied on as the principal means of mitigating damage. Immobilizing agents continue to offer promise as useful nonlethal tools for population reduction programs. Exploration of the use of tribromoethanol in coot capture is described, and the potential for other bird management techniques is discussed.

Bird problems in California pistachio production

In 1984 studies were initiated to identify the bird species causing damage to pistachio nuts, quantify the losses, and explore possible methods for alleviating bird losses. The first year's field observations were made to identify and determine the level of activity of the various depredating bird species in the orchard. Field samples of nuts were collected to assess the levels of damage occurring in representative orchards. A mail survey of all commercial pistachio growers in California was conducted to determine which bird species growers believed were the cause of nut losses, the extent of damage they have experienced and what, if any, bird control methods they have used. The objective of the second year was to further evaluate production losses due to crows and scrub jays. During the damage season, evaluation of various types of baits for crows and scrub jays was made in several pistachio orchards. Finally, with most growers reporting the use of shooting to frighten and disperse the birds from the orchard, an initial effort to evaluate shooting as a control method was made.

The economic importance and control of vertebrate pests of graminaceous crops with particular reference to rice (Oryza sativa) in Nigeria--a review

Graminaceous crops, especially rice (Orzya sativa), have within the last years in Nigeria, surged to be of utmost economic importance, not in improving the economy but in depleting the country of fast foreign exchange. Attempts at improving and massively increasing the production and cultivation of rice (and other graminaceous crops) to meet the enormous demand have proved abortive. This is mainly a result of the ineffective control measures applied against destructive avian pests that sometimes reduce rice plantations to nothing. Much research is still needed to enhance better and effective control strategies.

Pest bird control with the avicide BCF 7000--Sun Oil refinery project, Tulsa, Oklahoma

The Sun Refinery at Tulsa, OK, presented a new and special type of problem that I had never faced before. The refinery is just across the Arkansas River from downtown Tulsa. Many species of protected birds roost and nest within the confines of the refinery proper and in the surrounding riverbank areas to the north, urban and manufacturing area to the east and southeast, rail yards to the south, and hills to the south and southwest. According to Sidney Cabbiness, Environmental Engineer for Sun, the following birds and other animals are known to make this area their home or feeding sites at least some time during the year: meadowlarks, scissortails, mallards, yellowthroat, killdeer, red-tailed hawks, sparrow hawks, red-winged blackbirds, mourning doves, mockingbirds, robins, grackles, magpies, crows, squirrels, red foxes, rabbits, raccoons, bobwhites, great blue herons, domestic cats, bald eagles, golden eagles, great white egrets, kingfishers, Canadian geese, blue geese, roadrunners, skunks, horses just outside the south fence, dairy cattle just to the west, and, of course, our pigeons, starlings and house sparrows. Hawks are prevalent year-round, and the eagles primarily winter at Keystone Lake, just west of Tulsa, and are known to feed up and down the river as well as occasionally on the tank farm. The problem species is starlings, more than 750,000, by my best estimate, along with about 3,000 to 4,000 pigeons. A few sparrows roost around the Club Room and on a loading dock, but they aren't the real problem. Regularly available registered products and techniques would have been either ineffective in solving the existing problem or too dangerous to use in such an environmentally sensitive area. Damage to the units from the droppings was extensive, but the potential health and safety hazards that the birds and their droppings presented to the employees were the primary factors in prompting Sun to seek outside professional help. The development of the avicide BCF 7000 and its use at this Tulsa site has provided a safe and effective solution for the problem. Starling reinfestation the following season (1985-86 winter) has been ZERO. No adverse comments or reactions were received by this office, or by anyone to my knowledge. Much work is still needed to acquire a federal registration, but we are well on our way to providing the pest control community with another much-needed tool.

Salmon poisoning disease: research on a potential method of lethal control for coyotes

Salmon poisoning disease (SPD) was tested as a potential method of lethal control for coyotes (Canis latrans). Fresh fish containing the agents for SPD was fed to 72 captive adult coyotes. Coho (Oncorhunchus kisutch) and steelhead salmon (Salmo gairdneri) from Oregon hatcheries were the principal species of fish used. Coyotes that ate the fish developed observable signs of SPD in a mean of 8 days. The overall rate of mortality was 50%, and death occurred in a mean of 20 days from consuming fish. Coyotes that died from SPD lost a mean of 32% of their body weight during the course of the disease. Other coyotes were fed preserved fish samples or administered oral or intraperitoneal treatments of lymph node matter from coyotes that died from SPD. In light of the relatively low rate of mortality observed, feeding coyotes fish to cause death from SPD appears to be a method of questionable value for controlling numbers of adult coyotes in areas of livestock production unless fish with a highly virulent strain of the SPD agent can be obtained.

Alternate toxicants for the M-44 sodium cyanide ejector

The M-44 sodium cyanide (NaCN) ejector is an important tool for coyote damage control. For greatest effectiveness, the ejected NaCN mixture must be a dry powder. NaCN readily absorbs and reacts with moisture to cause solidification or "caking" in M-44 capsules. Because it is difficult to seal the capsules water tight, caking has been a chronic problem ever since NaCN ejectors were introduced over 40 years ago. The toxicity and caking properties of three alternate compounds are reported in this paper. Comparative toxicity tests were made with M-44 ejectors containing NaCN, potassium cyanide (KCN), calcium cyanide (CaCN), and methomyl. Five to eight pen tests on coyotes or dogs were conducted with each compound. NaCN was tested on both coyotes and dogs. Except for one coyote that survived a dose of CaCN, each test animal died after pulling an M-44 and receiving a full charge of ejected toxicant. Average lapsed times from pull to first observed symptoms were 31 seconds for NaCN, 34 seconds for KCN, 63 seconds for CaCN, and 2 minutes for methomyl. Both NaCN and methomyl were lethal in all pen tests, yet coyote recovery rates (carcasses found/coyote pulls) in the field were 80% for NaCN and only 24% for methomyl. This difference was attributed to the faster action of NaCN. KCN and CaCN were not field-tested, but results from captive coyotes indicate that KCN would be about as effective as NaCN and CaCN would be less effective. None of the three alternate compounds offers enough advantage over NaCN to warrant the expense of registration, since NaCN is already registered.

Secondary toxicity of coyotes killed by 1080 single-dose baits

Carcasses and viscera of coyotes poisoned by Compound 1080 (sodium fluoroacetate) in single-dose tallow baits (SOBs) were fed to 3 coyotes, 3 domestic dogs, 4 striped skunks, and 15 black-billed magpies to determine if these species would be poisoned secondarily. Test subjects received no food other than tissues from poisoned coyotes for periods of 14 to 35 days. Total amounts of contaminated coyote tissues consumed by dogs, coyotes, skunks, and magpies, respectively, averaged 67, 152, 117, and 371% of body weight. Except for one skunk that refused to eat, no mortalities occurred, and no evidence of poisoning was seen. The average 1080 residue in tissues fed to nontarget animals from coyotes poisoned by one to three SDBs (5 to 15 mg 1080 per coyote) was 0.29, 0.30, and 0.31 ppm in muscle (n = 15 coyotes), small intestine (n = 13), and stomach tissue (n = 8), respectively. Highest residue levels observed were 0.66 ppm in muscle, 0.79 ppm in small intestine, and 0.76 ppm in stomach tissue. These concentrations were apparently too low to cause secondary poisoning in the species tested.

Private costs of predator control in New Mexico in 1983

A survey was conducted by the New Mexico Department of Agriculture in early 1984 to determine costs incurred by livestock producers to control predation on livestock during 1983. Out of a sample of 1,848 producers who were sent questionnaires, 706 (38%) usable responses were returned. The respondents reported having about 30% of the peak number of sheep and lambs and 19% of the peak number of range beef cattle and calves, respectively, estimated to have been in New Mexico in 1983. Total cost reported by 306 respondents who had costs, not including donations to the New Mexico cooperative Animal Damage Control program, was about $450,000. Trapping (including the use of traps, snares, and M-44 devices) accounted for 38%, coyote drives 15%, "other nonlethal" methods 14% (including predator-resistant fences, night penning, shed lambing, etc.), and aerial gunning 12% of total cost. Sight or trail dogs accounted for 5%, ground shooting 1%, guard dogs 5%, sheepherders 7%, and miscellaneous costs (generally included labor and vehicle or horse expenses to check for predator sign and kills) 2% of total reported costs. Lethal methods comprised 72% and nonlethal methods 26% of the total cost. Sixty-seven percent of the sheep producers who had costs for predator control reported spending money on one or more nonlethal methods; of these, 29% spent money on guard dogs, 22% on herders, and 52% on "other nonlethal" methods. A generalized approximation of the total costs incurred by livestock producers in New Mexico in 1983, based on the survey results plus private contributions to the New Mexico cooperative Animal Damage Control program, was $1.8 million. Adding this estimate to the total estimated value of sheep and cattle lost to predation brought the total economic impact of predation on the livestock industry in New Mexico in 1983 to $5.3 million. The data suggested private predator control costs are approximately one-third of the economic impact of predation on livestock producers.

Biological status of mountain lions in California

We review the history of management and present legal status of mountain lions in California, the political situation leading to the present status, and some of the biological factors that have been controversial, particularly relating to population status and trends. We summarize past and current research efforts related to mountain lions within California, noting that the amount of effort devoted to mountain lion studies in California is greater than has been recognized. We review population trends and estimates, and we describe past and current management methods, including bounties and other methods to resolve predation incidents. Human-lion encounters are discussed, including a history of lion attacks on humans within the U.S. We recognize that management of the mountain lion in California affects many individuals and interest groups and is therefore a political decision.

Trends of predator losses of sheep and lambs from 1940 through 1985

Mortality of sheep and lambs from all causes and from predator losses from 1940 through 1985 for the United States is presented including economic aspects. Lamb losses from all causes were 9% of the lamb crop in 1940 and were generally higher thereafter and reached a peak in 1978 of 14%. Losses of sheep 1 year old and older from all causes were 7.5% in 1940, remained somewhat higher through the '60s, and then declined to a low of 5.2% in 1985. Calculation of predator losses were based on an upward trend of lamb losses relative to sheep losses with increasing losses to predators. Estimates of predator losses were conservative and probably were underestimated. Predator losses were lowest in 1940 at 2.85%, increased during World War II, remained moderately high through the '50s, and then increased to a peak of 6.07% of all sheep and lambs in 1977. Losses declined following the advent of the parvovirus in 1978 to a low of 5.24% in 1981 and then increased to 5.69% in 1985. Monetary losses from predators showed a steady increase from $13 million in 1940, to almost $90 million in 1979, and almost $69 million in 1985. Total losses from 1960 through 1985 were $1.2 billion. Predator losses as a percent of net income increased from 23% in 1940 to 26% in 1960, and to 78% in 1979. After reduction in predator losses due to the parvovirus they were still 60% of net income in 1985. Obviously, predator losses have been a dominant factor in the decline of the sheep industry.

A changing approach to dingo control in western Australia

The traditional method of dingo control on sheep properties in Western Australia relied on labour-intensive trapping and baiting. A cost/price squeeze in the rangeland sheep-grazing areas around 1970 forced a revision of these practices. Research was conducted on dingo biology, habitat preference and use, movements, social organization, and damage to livestock. The data demonstrated the territorial nature of dingoes, that they usually occur in groups of 2 to 15, that long movements are rare, and that they quickly learn to harass and kill sheep. Aerial baiting trials using factory-manufactured baits and baits prepared from fresh meat demonstrated that an adequate level of control could be achieved in a buffer zone adjoining sheep-grazing areas to minimize the movement of dingoes onto sheep areas. Baiting success was higher for young and lone dingoes with the use of individual meat baits, and probably with a high-bait density and a low-prey population. The research findings have been largely incorporated in a refined strategy for dingo control based on the buffer zone concept at reduced cost for control. If the cost and results of the research are assumed to have led to the benefit of lower control costs over the next 20 years, a benefit:cost ratio of about 2.5:1 is indicated.

Eradication and control of feral and free-ranging dogs in the Galapagos Islands

On the Galapagos, as with other remote islands lacking native predator populations, selection for behavior in native species which leads to their avoidance of predators has been relaxed and island fauna are often at their mercy. The author describes the history of canid introductions to the Galapagos beginning in 1832. Feral dogs’ impact on endemic fauna is summarized. Eradication and control efforts, both in coastal areas and in highlands, is described in detail along with results of these efforts, which included shooting, use of both baits and water stations containing sodium fluoroacetate (1080), and capture and chemical vasectomy on males.

Predator damage control: 1980 to 1986

This discussion is an update from Wade (1980) which summarized executive and other decisions relating to cancellation of the predacides in 1972. This review continues that summary of major events from January 1980 to the present. Major political factors, predator damage control, and research findings during this period are briefly discussed. A chronology of administrative and judicial decisions and related events is appended (Appendix A).