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:
Volume 9, 1980
The author’s keynote address touches on a number of issues and trends that affect the field of wildlife management, including a growing anti-hunting sentiment in the U.S., the public’s changing attitudes toward hunting and trapping, and the role of predator control in wildlife management.
Research into the biology and control of pest birds in Somalia has continued intermittently since 1971 under UNDP funding of four projects. Data have been gathered on the identification, distribution, and status of the principal pest species to agriculture. These species include the red-billed Quelea (Quelea quelea), of which northern and southern races occur, and several other ploceid weavers (Ploceus spp. which may damage cereal crops. The movements, food habits, and corresponding impact of these species on agriculture in Somalia are discussed in detail. As a result of the information obtained during these years of research, emphasis has recently shifted to developing the indirect control capacity of the Bird Control Unit and evaluating methods for directly protecting a crop. Scouting teams for locating concentrations of pest birds have been organized and initial control operations undertaken. Trials of frightening and scaring devices and techniques, physical barriers, and chemical repellents have been evaluated, but only on a limited scale and with variable results. The whole arena of managing bird pests is new in Somalia and progressing slowly. However, the necessary framework is being established upon which a crop protection strategy, integrating methods of indirect and direct control, can be implemented.
In an effort to reduce damage by house finches (Carpodacus mexicanus) to grapes, field trials were undertaken in two red winegrape (Pinot Noir and Pinot Chardonnay) vineyards in California using prebait (rape seed and canary grass seed) followed by baiting with these same seeds treated with a hydrochloric acid and 4-aminopyridine (Avitrol) solution. Seed was placed in V-shaped troughs placed 1-3 feet above the vines; treated seed was blended in a ratio of 2 untreated seeds to 1 treated seed, and 3 parts canary grass seed to 1 part rape seed. Prebait seed was replaced with treated seed when estimated maximum house finch visitation occurred, and was exposed from 1 to 4 days, with removal when house finch feeding from troughs ceased; the prebait and treatment schedule was then repeated as necessary until harvest. Bird counts were made throughout the trial, and winegrape damage assessment was conducted. In one test vineyard, early in the trial damage in the treated plot was assessed at 3% while damage in the control plot was insignificant, and house finches abandoned the test site. In the other test vineyard, the treatment plot received 7% damage while the two control plots received 17% and 13% damage, respectively. As a result of the treatment, grape damage was reduced approximately 50% as compared to bird damage the previous year. Data support the conclusion that Avitrol-affected house finches may stimulate an avoidance reaction among other flock members.
Levels of bird damage to sorghum in the Awash Basin of Ethiopia and the effects of the control of quelea nesting colonies (1976-1979)
Quantitative assessments of bird damage to lowland sorghum (Sorghum bicolor) were made annually from 1976 through 1979 in the major growing areas associated with the Awash River Basin. Results indicated that the red-billed quelea (Quelea quelea) can be an important limiting factor in the overall production of this cereal, and that damage can be locally severe. Lethal control of quelea breeding colonies found along the Awash River and at Lake Zwai was undertaken in September/October of both 1978 and 1979. Subsequent assessments showed substantially less bird damage in both years and overall losses were minimal.
Measures to exclude gulls from two coastal domestic water supply reservoirs in Orange County have included the use of shotguns, exploding shell cartridges and carbide cannons. Alternative methods were explored which hopefully would prove more effective and less costly than the harassment techniques being employed. The installation of a network of spaced wire over the reservoir water surface has successfully excluded gulls from these bodies of water.
Four studies were conducted in January 1977-79 in Kentucky and Tennessee. Two of these studies were to determine the feasibility and effectiveness of selectively reducing starlings from mixed blackbird/starling winter roosts by baiting their congregating areas with Starlicide Complete® pellets. The two remaining studies dealt with determining bait preference of starlings and nontarget birds for two formulations of pelleted baits (Layena and corn). Starlicide baitings were fairly selective for starlings, but nontarget hazards were encountered. Starlings showed no significant preference for either type of pelleted bait, but nontargets preferred corn over Layena pellets. Methods are suggested to minimize nontarget hazards from baiting starling congregating areas.
Frightening devices and other methods of dispersing roosting blackbirds and starlings are described along with the techniques for their proper application. In a study in the southeastern United States, exploding shotgun shells and noise bombs were used to disperse roosts of up to 1 million birds. Five roosts containing up to 1 million blackbirds and starlings were 96 to 100% dispersed by two to five people during three to eight evenings of harassment. Dispersal cost between $80 and $535 per roost.
Several methods were evaluated for protecting polrethylene irrigation pipes against pecking damage caused by the Syrian woodpecker (Dendrocopos syriacus). Only by burying the pipes in the ground damage was effectively prevented. Other methods studied, the use of the game repellent Arbinol, covering the pipes with polyethylene sheets, and growing a weed cover, though reducing the rate of the damage, proved not to be sufficiently effective as an economic solution of the problem.
Factors responsible for the successful establishment of exotic avian species in southeastern Florida
Presently southeastern Florida has at least 24 established exotic avian species from both New and Old World families. This much man-modified region of Florida is characterized by the Atlantic Coastal Ridge in Palm Beach, Broward, and Dade Counties and the Florida Keys of Monroe County. Because of the draining of the Everglades to the west, the filling of the mangroves on the seaward side, and the accompanying urban-suburban sprawl, many exotic plant species have invaded the Ridge thus preparing the environment for introduced birds. The red-whiskered bulbul, Pycnonotus jocosus, illustrates this point. Host exotic avian species have appeared and colonized within the last 20 years, probably the result of a developed preconditioned environment and improvement in the transportation of exotic wildlife. Birds which have succeeded are generally those which are non-migratory, gather in communal roosts in the non-breeding season and are not obligate but generalized feeders. The exotics may be filling niches not presently filled in Florida's depauperate avifauna.
Considerable effort has gone into developing and testing the various management methods for keeping blackbirds out of cornfields, but little work has been directed at understanding the relationship of the birds or the damage control methods to the other organisms within cornfields. This report shows that in a number of cases insects may influence bird-damage control programs. It points out the complex interaction among organisms that can occur in agricultural crops and the importance of considering pest control from an integrated view instead of from a single-species basis.
The general public in the state of Georgia is faced with at least 45 kinds of vertebrate animal damage control problems. Their questions asking for problem solutions are often directed to Georgia Cooperative Extension Service agents in 156 counties. County agents in the Atlanta Metropolitan Area receive an average of 325 requests for vertebrate pest control information a year. Agents in the Coastal Plain Area receive an average of 140 questions per year as does the Extension Wildlife Specialist. The combined total of vertebrate animal damage control questions received by all agents is approximately 60,000 per year. Typically difficult questions are referred to the wildlife specialist while common questions are handled by local agents. The most frequent requests concern problems in homes, other structures, and yards. Requests concerning agricultural losses in gardens and on farms ranked next. Requests to solve predator damage problems ranked last. Extension information is very effective when applied to problems with simple solutions. Vertebrate pest problems with complex solutions usually need the direct involvement of a specialist to be effectively solved.
This report lists toxicants and repellents for birds, tracking powders for rodents, chemosterilants, deer repellents, dog and cat repellents, fumigants, etc.
The control of roof rat Rattus rattus involves not just chemical and physical suppression, exclusion, and sanitation in an integrated environmental manipulation approach, but in order for the environmental manipulative technique to work, the environmental-behavioral habits of the individuals living in these roof rat infested areas must be modified. Once a target area of known rodent infestation has been initially impacted and environmentally improved upon, the task by the homeowner to continue to practice environmental manipulation must be ongoing. Continued maintenance of the environmentally improved area by staff knowledgeable in environmental manipulation and behavioral modification is the only way to insure that the area will continue to have such reduced carrying capacity so as not to allow roof rat reinfestation. Without continued maintenance, roof rat populations will return to an environmentally improved (manipulated) area in four years' time.
Recent developments in anticoagulant rodenticide resistance studies: Surveillance and application in the United States
Since anticoagulant rodenticide resistance was first discovered in the United States in 1971, it has become apparent that the phenomenon is widespread. In cooperation with the Center for Disease Control, a nationwide surveillance program was initiated in 1977 to obtain statistically valid samples of rats from federally funded projects of the Urban Rat Control Program. A summary is given of the basic sampling, testing, and analysis components of this study. Problems encountered in all aspects of the first three years of the program are discussed along with results from the 40 completed samples. The 16 cities with significant Anticoagulant Resistance Problem Areas are distinguished from those in which resistance has merely been observed. Levels of resistance in various rat populations are discussed and recommendations are made in support of integrated pest management programs. Recent findings from retesting resistant rats, half of which die, are presented with regard to application of the surveillance program.
Plague studies in California--The roles of various species of sylvatic rodents in plague ecology in California
The status of our knowledge of the roles of various sylvatic rodents in plague ecology in California is reviewed. Two theories, Pavlovsky's doctrine of focality of zoonotic diseases and Baltazard's proposal that plague is maintained in nature in resistant rodent species, form the framework for our understanding of the occurrence and persistence of plague. The concepts of resistance, reservoir species, susceptibility, and recipient species are defined and discussed. The ecological attributes that appear to enhance the role of certain rodent species as reservoirs are proposed, and the ecological features that appear to produce epizootics are briefly outlined. Based on current information, the roles of individual species of rodents, rabbits, and some insectivores are presented and discussed in relation to epizootic potential and the epidemiology of human infection. Man's role in plague ecology leading to greater exposure to sylvatic plague is emphasized.
The systematic study of vertebrate pests in agriculture in Nigeria spans only two decades. The species composition of vertebrate pests has been determined in crops like cocoa, oil palm, maize, and rice. The ecology of a few important pest species has been studied. Because of its devastating destruction of many graminaceous crops over most parts of Africa, the red-billed quelea (Quelea quelea) has been studied more intensively than other avian pests. Other avian pests include the village weaverbird and the bush fowl. The ecology of some mammalian pests has also been studied: a research programme has been started at the University of Ibadan on the management, domestication, and breeding of one of the most notorious rodent pests, the cane rat (Thryonomys swinderianus). The present report presents an up-to-date knowledge of the identity of those mammals and birds that cause damage on farmlands and in stores.
From the fall of 1977 through late spring of 1979, periodic examination of female ground squirrels in the low oak woodlands of southern Tulare County revealed that as much as 20 percent of the reproductively active females bred a second time within a given breeding season. This began to occur 50 to 80 days after the beginning of the breeding season. Evidence of litter loss from abortion was inapparent in 1979, but grossly obvious uterine inflammation was seen in 2 percent of the females in 1978. Neonatal losses were undetermined. Rebreeding appeared to occur in the older females, 2 years and older, and considering that older females probably constitute 35 percent of the breeding females, 20 percent breed-back would seem to be quite significant.
Damage to conifer seedlings by pocket gophers (Thomomys spp.) is a major factor limiting reforestation in the western United States. To control gopher populations and reduce damage, the U.S. Forest Service annually treats thousands of hectares with strychnine alkaloid bait. Because an underground application of strychnine bait could pose a threat to other species, we monitored small mammal populations before and after a baiting operation conducted in 1979 on the Targhee National Forest, Idaho. Although two deer mice (Peromyscus maniculatus) recovered within baited areas were killed by strychnine, live-trapping revealed no differences in small mammal populations before and after baiting. Thirty yellow pine chipmunks (Eutamias amoenus) and one northern flying squirrel (Glaucomys sabrinus) were fitted with radio transmitters before treatment. Twenty-four of the chipmunks, and the flying squirrel, survived to the end of the study. Transmitter signals were lost on three chipmunks before treatment and they were unaccounted for. Two chipmunks died during the study and contained strychnine residues in body tissues. The remaining chipmunk appeared to have been killed by a predator.
The black rat (Rattus rattus) causes severe damage to coconut (Cocos nucifera) crops in Colombia. These rodents climb to the crown of producing palms and often nest there. Damage results from the rats gnawing the shells of the coconuts until they penetrate to the endosperm; the perforated nuts will fall within a period of 15 days and are unsuitable for harvest. Since 1972, the Colombian Agricultural Research Institute (Instituto Colombiano Agropecuario or ICA), through its Vertebrate Control Program, has been conducting a series of investigations to obtain information about the characteristics of this damage and the best means of reducing it. Damage surveys in several of the principal coconut-producing areas reveal a high percentage of crop loss (e.g., Tumlaco - 20%, San Andres Island - 34%, and Gorgona Island - 60%) and illustrate the seriousness of the problem. The lack of water (i.e., rainfall) during the dry season seems to be associated with increased damage. In some areas, such as San Andres, the planting density is excessively high. Hence, physical barriers such as metal bands on the trunk are ineffective -- the proximity of the palms allows the rats to transit easily among adjacent trees on overlapping fronds. Our observations indicate that chemical control using anticoagulant baits placed in the palm crowns, significantly reduces damage. The effect of a single baiting can last up to six months, with the length of the effect dependent upon cultural practices implemented after treatment (e.g., maintaining cleanliness of area, weed control, etc.). At present, chemical control and associated cultural practices is the program recommended by ICA for reduction of rat damage to coconut crops in Colombia.
Although bait shyness has long been recognized as a problem to be overcome in the control of vertebrate pests, it has recently been suggested that the phenomenon might be turned to an advantage and used as an alternative, non-lethal form of control. Unfortunately, this technique has not proven to be as useful as hoped, as the work which has been done on coyotes is inconclusive at best and some recent work on rodents has cast serious doubts upon the method's potential. However, an extensive literature dealing with the formation of poison-based food aversions now exists, and insights gained from these studies can be used to increase the efficacy of traditional, lethal control techniques. For example, the efficacy of pre-baiting may be greatly increased if the pre-bait is treated with a nontoxic flavor which mimics the flavor of the subsequently used toxin, even if this non-toxic flavor decreases the acceptability of the pre-bait.
Vacor (RH-787), a relatively new rodenticide, was evaluated for the control of Rattus rattus rufescens. The symptoms of paralysis in hind limbs were observed after feeding it to rodents. The susceptibility to this rodenticide in Rattus rattus increased with the increase in its concentration. Experimental observations revealed that RH-787 bait with 0.0125% concentration affects the reproductive biology of the rats. Bait with 0.025% Vacor proved sublethal and within 5 days 70% mortality was observed, while 100% mortality was observed when rats were fed with 0.05% Vacor
A brief review of deratization carried out in Budapest (2 million inhabitants) is given. As a result of an extensive eradication project initial infestation level of premises amounting to 331 decreased below 0.5%. Materials and techniques employed for the preservation of a rat free state as well as the method how to determine the size of the remainder of the rat population are described. "Idealized premises" were introduced allowing comparison between rat infestations of various areas. Report on the relationship between rat population and temperature, on the areal dispersion of population and on how re-infestation occurs. Finally, conclusions are drawn based on the favorable results achieved.
The collared pika, Ochotona rufescens, has been recorded as a serious pest in apple orchards in the uplands valley of Ziarat in Baluchistan. In the winter, when the natural vegetation is lacking, the pikas debark the apple tree trunks or branches resulting in the killing of the tree and reduced fruit production. In summer, damage to wheat, corn and potatoes is also very severe. It is estimated that pikas cause hundreds of thousands of dollars (US) in annual apple production losses. The apple production in Baluchistan accounts for about 35 percent of the total provincial income through food production. During the six years (1974-1979), the winter of 1973-74 was noted for heavy damage to apple trees and thereafter it declined steadily. The control measures evaluated were of various kinds among which repellent "Ostico" was very effective in protecting the trees. Poison baiting with brodifacoum (0.005%), Vacor (1%) and thallium sulphate (1%) were also effective in reducing the pika population. To alleviate damage caused by pikas, the farmers also practice some traditional protective methods which in some cases are quite effective but very laborious.
Mountain beavers (Aplodontia rufa) cause considerable damage to forest trees in the Pacific Northwest. Feeding injuries result in mortality, growth losses. deformity of trees, and understocked plantations. Losses are most severe in new plantations with significant damage problems also occurring in sapling stands. Trapping, and placing physical barriers around individual trees, are the most common methods of control. Both methods are costly but effective in reducing damage.
Two acute rodenticides, zinc phosphide and Vacor, at different concentrations were tested on the rice field rats (Rattus argentiventer) and the bandicoot rats (Bandicota indica) with a choice-feeding procedure. It was found that zinc phosphide at 0.5%, 0.8%, 1.6% caused 30%, 30%, and 60% mortality, respectively, to R. argentiventer, and at 1.6% caused death only 30% to B. indica, whereas Vacor at 0.5%, 0.8%, 1.6% caused 70%, 60% and 80% mortality, respectively to R. argentiventer and this compound at 1.6% killed 60% of B. indica. Five anticoagulants, Actosin-P, warfarin, Racumin, brodifacoum, and chlorophacinone also were tested on R. argentiventer and only brodifacoum was tested on B. indica at an appropriate concentration with a non-choice feeding procedure. It was found that with-one day consumption of the poisoned bait brodifacoum 0.005% is the only anticoagulant that caused 100% mortality to R. argentiventer and B. indica, whereas, Actosin-P, warfarin, Racumin, and chlorophacinone killed 20%, 20%, 30%, and none of R. argentiventer, respectively.
The vital question, as to the cause of the permanent increase in field rat populations throughout most tropical and subtropical areas, has been the subject of researchers and fieldmen during the past years, in the hope of finding an answer to this problem. Man has made his way through history wherein he was gradually able to renounce nature and establish his own man-made cultural frame. Unlike other mammals, man has no natural instincts to guide him through life. Brain and spirit have to compensate for lack of physical capabilities and instincts. Man was forced to change his natural surroundings in order to serve his special and ever-growing needs. Survival meant not only using nature but more so changing it in order to develop his culture. The field rat has become man's "cultural treader"! Myomorpha is the largest suborder of the Order Rodentia. Of the 1700 rodents known to man, more than 1100 belong to this group. The greater part of the Myomorpha species are found within two families, which are Cricetidae with about 567 species and Muridae with about 475 species. Most of these rodents live either in trees or under the ground. They rarely collide with man's interest. Only a few rodent species have become "field rats" and seem to dwell in and utilize man's cultural steppe. Some species have even become cosmopolitan and are found in Europe. Asia, Australia, Africa, South, Middle, and North America. leaving only Madagascar and New Zealand without infestation. Field rats are considered the most successful mammals including man. This is due to their fine balance of curiosity and caution, to their instructive behavior and to their well-balanced, often highly developed social structure. The field rat finds, in the man-made or man-modified environment. an almost ideal habitat. Subsistence farming, when looked upon from an ecological viewpoint, has little impact in harming the natural environment. Nature's equilibrium is maintained with this method. Field rats have but a meek chance to dwell within the frame of the traditional farming system.
The habits and influence on the environment of the old world porcupine Hystrix cristata L. in the nothernmost part of its range
The crested porcupine (Hystrix cristata L.) has been shown to have considerably increased in numbers and to have occupied new territories in Tuscany, which is the northernmost part of its range. New data on its ecology and biology, and the negative effects of an excessive density of these rodents on the rural and natural environment are reported. Since this species is protected by law in Italy, because of its high value from the faunistic point of view, some possible techniques, to be improved upon, for the capture and redistribution of live specimens are discussed.
Population studies on gerbils of the western desert of Egypt, with special reference to Gerbillus andersoni DE Winton
Population studies on the gerbil, Gerbillus andersoni, were carried out in Omayed in the Western Desert of Egypt during the period from July 1976 through August 1978 inclusive. Studies included determination of the sex ratio in the different age and weight groups, as well as seasonal changes in this ratio. The mean weight and age at the onset of maturity and the reproductive activity of both sexes were determined. The study also included seasonal changes in mean body weights of both sexes, those of the testes in relation to body weights, as well as changes in the length of the testis and of the cauda epididymis. Changes in the age structure of the population were also studied.
Woven-wire fences, 2.4-m-high, have proven to be deer-proof and economically feasible for some apple orchards planted to semi-dwarf and dwarf trees, under high-density planting systems. The factors included in a benefit-cost analysis are described, and a formula is given to facilitate a decision about the economic feasibility of investing in a fence of this type.
The nine-banded armadillo (Dasypus novemcinctus) has been successful in extending its range throughout the southeastern states. It occupies such a diverse range of habitats that its effects on its surroundings depend largely on where it is located. It offers benefits from its burrowing and eating patterns by creating dens for furbearers and destroying large quantities of injurious insects and their larva. Those same activities in urban and suburban areas are now being recognized as a source of considerable nuisance and moderate damage. Damage is most severe from July through early November. They have been recognized in connection with several diseases of public health importance. Control is possible in urban areas by use of live traps of various types. Rural control is possible through a wider variety of methods. The armadillo's position in American culture and social life offers a challenge for future management which should not be ignored.
Because of the limited resources of most Latin American countries, an ecological strategy for controlling bovine rabies through elimination of vampire bats is proposed instead of attempting total eradication. The strategy is essentially a combination of one or more of the anticoagulant control techniques applied with knowledge of the epizootiology of vampire rabies. Since rabies outbreaks in vampire bats are migratory, each outbreak is studied to determine the direction and velocity of its course, then an area is selected in its path where vampires are eliminated, forming a barrier and resulting in elimination of the outbreak.
The changes in a feral pig population associated with 1080 poisoning were examined. There was a 58.1% reduction in population size after poisoning with no age-specific effect. The population size increased over 11.5 months after poisoning at an observed instantaneous rate of increase per year of 0.57. The results are discussed relative to feral pig control.
The red kangaroo is the dominant native grazing herbivore over much of the arid rangeland area of Western Australia, where the species exists side by side with introduced livestock. The numbers are such that red kangaroos can be utilized as the basis for a commercial harvesting industry provided the population is managed on a sustained yield basis. The WA Management Programme is designed to take account of the need for conservation of the species and for protection of the livestock industry and the rangelands on which both kangaroos and the livestock industry depend.
This review summarizes executive and other actions relating to cancellation of the predacides in 1972 and related events. A chronology of these actions and events is appended (Appendix A). Predator damage control operations. and research findings over the past decade, are briefly reviewed and related political decisions are discussed.
Conditioned food or flavor aversion has been proposed as a method to stop coyote predation on sheep. The method entails treating sheep carcasses or meat baits with an emetic, lithium chloride (LiCl), and scattering them on sheep ranges. Theoretically, coyotes eat the baits, become ill, and subsequently desist from killing and eating sheep because they associate sheep flavor with sickness. In recent studies, coyotes have not formed prey aversions. Coyotes avoided baits because of LiCl flavor rather than prey flavor and prey-killing aversions were not found. We conducted a study designed to find the best LiCl-prey flesh concentration to produce bait aversion in coyotes, and to test the transfer of bait aversion to a prey-killing aversion. Baits with 1 g LiCl per 500 g prey flesh produced the strongest aversion to untreated baits, but coyotes conditioned to avoid prey baits made at this concentration killed and ate live test prey as frequently as coyotes with no conditioning. The lack of transfer from bait aversion to prey-killing aversion suggests that LiCl bait aversion will not prevent coyote predation on livestock.
Data about the efficacy of predator damage reduction programs are shown for predation loss studies with control, loss studies without control, complaint resolution or success rates, and predation predator-capture sequences. This combined evidence indicates that animal damage control programs are reducing predation on livestock.
This paper examines and evaluates the use of strychnine baits and cyanide guns for coyote (Canis latrans) control by livestock producers in Alberta. Livestock predation occurred almost exclusively during spring, summer, and fall; livestock predation was negligible during winter. In contrast, use of toxicants was negligible in spring, distributed rather evenly through the summer and fall, and most intense in mid-winter. Forty-eight percent of the producers set toxicants in response to predation, and 1/2 of these apparently resolved their predator problems. Fifty-five percent of the producers set toxicants for preventive control, predominantly during October-February when the effectiveness of control was probably negligible or at least minimal. Overall, the program may be less than 30% effective. The producer-training program must be re-examined in an effort to make coyote control more effective. Preventative control with toxicants, where necessary, should be conducted immediately prior to the whelping season or no more than a month in advance of anticipated livestock losses. Changes in livestock management must be emphasized.
In laboratory tests with adult coyotes (Canis latrans) a pyrotechnic fumigant containing two active ingredients, sodium nitrate and charcoal, was found to be just as effective as the U.S. Fish and Wildlife Service Gas Cartridge that contains six active and two inactive ingredients. The two-ingredient cartridge produces high concentrations of carbon monoxide. Field tests with cartridges containing 240 g of 65% sodium nitrate and 35% charcoal produced a 96% mortality rate in coyote pups. A cartridge containing 65 g of 65% sodium nitrate and 35% charcoal was effective in both laboratory and field tests on wild Norway rats (Rattus norvegicus). In field tests conducted at a rat-infested cattle feedlot, there was a 77% average (35% to 95% range) reduction in numbers of reopened burrows after fumigation as compared to pretreatment figures. Sodium nitrate and charcoal are not dangerous chemicals. The acute oral LD50 for both sodium nitrate and charcoal is greater than 3,000 mg/kg in rats, and there was no potentiation when given in combination at 3,000 mg/kg. No signs of secondary toxicity were observed in bobcats (Lynx rufus) fed rats killed by fumes from burning sodium nitrate and charcoal. Since gas cartridges are used underground, potential hazards to humans and the environment are nil. When the cartridges are used properly, they are effective devices for controlling vertebrate pests such as coyotes and rats.
Of New Zealand’s exports, 80% are agricultural products, and therefore important to the nation’s economy. The Agricultural Pests Destruction Council’s function is to protect agricultural production from damage caused introduced vertebrate pests, in particular, the European rabbit (Oryctolagus cuniculus); Australian opossum (Trichosurus vulpecula); hare (Lepus eurpaenus); and two species of Australian wallaby, the Damma or (Macropus eugini) and red necked or bush (Macropus rufogrisea). Staff training and public relations are the two main approaches to ensure that we can use toxins, particularly 1080, safely and with the minimum of restriction. The staff training program and public relations efforts are described in detail.