Vertebrate Pest Research Articles

Strength and persistence of conditioned taste aversion in rats: evaluation of 11 potential compounds

Conditioned taste aversion (CTA) occurs when animals associate the taste of a food with illness and subsequently avoid that food. CTA can be experimentally induced by adding an undetectable, illness-inducing chemical to food. The use of CTA has been suggested as a humane, non-lethal method for vertebrate pest control. The present study tested the ability of the following 11 chemicals to generate CTA in laboratory rats Rattus norvegicus after a single oral administration: thiabendazole, levamisole hydrochloride, xylazine, copper sulphate, caffeine, ipecacuanha, nicotine, aspirin, fluoxetine hydrochloride, clotrimazole and nifedipine. Thiabendazole, levamisole, fluoxetine, and clotrimazole induced strong, long-lasting CTA. No extinction of the aversion was observed over 14 weekly food presentations after an initial administration of thiabendazole. An attenuation of the aversion was noted for rats dosed with levamisole and fluoxetine, although the average food consumption of these groups remained significantly lower than that of controls. Persistence of CTA was negatively related to pre-conditioning food consumption by individual rats.

Management of wildlife-human conflicts in Israel: a wide variety of vertebrate pest problems in a difficult and compact environment

Although Israel is a small country, it sits at the junction of three continents, and has an especially rich diversity of ecotones and wildlife. In addition, Israel serves as a narrow land-bridge on the major migratory route for millions of birds between Eurasia and Africa. Competing with all this wildlife for living space is a relatively dense human population. Israel is quite conservation-minded with strict wildlife protection laws and very little hunting. All these factors contribute to a situation in which there is much human influence over whatever available habitat is left for wildlife. Consequently, wildlife-human conflicts are common and diverse, but are dealt with mainly with non-lethal methods. Millions of migratory birds cross through Israel and share Israel’s small airspace with the Israeli Air Force (IAF). Israel is especially active in Bird Aircraft Strike Hazard (BASH) issues, which are controlled by a variety of means, including real-time radar information of migratory birds, habitat management, and use of border collies at airfields. Wildlife in Israel are vectors for human diseases (e.g., leishmaniasis, rabies, and West Nile fever). To prevent rabies epidemics, Israel has recently begun successful use of oral rabies vaccination (ORV) for jackals (Canis aureus) and foxes (Vulpes vulpes).

Vertebrate pest management in Victoria -- managing community expectations

Author(s): Regan, Kerry | Abstract: The impact of mammal pest animals, including the rabbit, fox, wild dog, feral pig, and feral goat, is one of the most significant threats to biodiversity, community values, and the economy in Victoria, Australia. The management of these pests is a complex issue involving all land types and land tenures. Both the Victorian Government and the community have expectations relating to the management of these pests; sometimes these expectations differ and finding solutions is difficult. To overcome this, the Victorian Government, through the Department of Natural Resources and Environment (NRE), has provided constructive debate on animal welfare issues and developed the Victorian Pest Management Framework (VPMF) to provide a consistent, strategic, and partnership-based approach to pest management, including mammal pests, on both private and public lands and waters. A key principle of the VPMF is that pest management is the responsibility of each land and water manager. Government only becomes involved where the action results in public benefit, incorporates shared investment principles, meets “duty of care” responsibilities, involves all stakeholders, and is consistent with State or Regional Catchment Strategies or Regional Action Plans. Government involvement also includes an accepted responsibility by public land managers to address damage caused to the community by pests that originate on public land and disperse onto adjacent private land. This responsibility is met through the Government’s “Good Neighbour Program.” The clear definition of expectations of community and Government detailed in the document has provided an agreed basis for all land and water managers to work together to develop and implement long-term, effective, safe and integrated management processes that protect and improve Victoria’s biodiversity and natural values and protect its productivity base.

Chemotherapy for Ecosystems: Use of Selective Toxins to Control Invasive Vertebrate Pests

A wide range of anthropogenic disturbances accompanied the spread of European settlement across Australia after 1788. They included widespread land clearance, changed fire regimes, harvesting/persecution of native biota, hydrological change through damming and irrigation, and the introduction of new species (Lunney et al. 1997; Calver et al. 1998 and included references). In concert, these changes have contributed to the extinction of 17 mammalian species (Recher & Lim 1990), representing over 6% of the original mammalian fauna and about half of mammal extinctions worldwide in the last 200 years (Dickman et al. 1993). It seems unlikely that the situation has stabilized, because over 17% of extant Australian mammal species have suffered range reductions since colonization (Dickman et al. 1993). Garkaklis et al. (1998, 2000) highlighted that the extinct mammals included many burrowers and diggers, so a suite of species involved in soil turnover, nutrient cycling, and plant propagule dispersal have disappeared. The disruption of such critical processes in the face of anthropogenic stressors is a critical tenet of health theory and suggests a loss of health in the as a whole (Costanza et al. 1998; Rapport 1998a,b). Recent experimental evidence confirmed the significant role of the invasive predators the red fox (Vulpes vulpes) and feral house cat (Felis catus) in the decline of several extant mammals (e.g., Kinnear et al. 1998; Risbey et al. 1999; Risbey et al. 2000 and, by implication, in the extinction of related species. Control of invasive predators is now a major part of recovery plans for a range of Australian mammals (Maxwell et al. 1996), primarily by baiting with the toxin sodium monofluoroacetate (commonly referred to as compound 1080, pronounced 'ten-eighty') (see Twigg & King 1991 for a major review). However, wildlife advocates are often uneasy about poisoning campaigns, so delicate public relations issues are involved (Calver & King 1986; Temple 1990; Marks et al. 2000). Cancers in human health are a tempting metaphor for the destruction wrought by invasive vertebrates to health (Robert Colona, quoted in Stokstad 2000; Stone 2000. In the case of cancers, there is evidence that physiological or psychosocial distress may depress immune system function and contribute to the onset of disease. Malignant cells then proliferate and may disperse, disrupting normal functioning and causing death. Similarly, anthropogenic disturbances may predispose to invasion by alien species, which displace indigenous species or modify processes and disrupt health. Furthermore, the metaphor can be extended to embrace treatments for cancer, with the use of toxins to eradicate or control invasive species seen as for ecosystems. Several authors have explored the parallel between human health and health (e.g., Ehrenfeld 1995; Rapport 1998a. Others have noted the power of such metaphors to encourage community involvement in environmental issues (O'Laughlin 1996; Calver 2000). In this paper, we extend the concept of the human health/ecosystem health metaphor as an educational tool, using the Australian case study of controlling destructive invasive predators by poison baiting. The destructive invasive species can be regarded as cancer cells in the and the poison baiting as to eradicate or contain them. The metaphor may allay community disapproval of poisoning as a control method by relating it to a familiar form of medical treatment used to protect human health. We develop the metaphor by: (1) overviewing the nature of human cancers and the applications, side effects, and limitations of human (2) overviewing characteristics of species introductions and the applications and limitations of chemical control of invasive species, with special reference to predator control in Western Australia as an example of ecosystem chemotherapy; (3) assessing the validity of the ecosystem chemotherapy metaphor by applying it to a range of and commenting on its potential in community education. The discussion reveals that the for ecosystems metaphor is robust in some cases and has potential as an educational tool. It is especially useful in highlighting the value of prevention, as opposed to cure, in the case of invasive species and emphasizing the importance of allowing local communities to make decisions about local health.

Determination of the sodium monofluoroacetate in serum by gas chromatography

Sodium monofluoroacetate (NAFAc) has been widely used for vertebrate pest control, such as rabbits in Australia. However, NAFAc is extremely toxic to all vertebrates and its use is restricted. Although this compound is stringently restricted, the occurrence of accidental and homicidal poisoning is na ever-present possibility.

Review of ecological restoration programme on subantarctic Macquarie Island: Pest management progress and future directions

Summary The establishment of exotic species of vascular flora and vertebrate fauna on subantarctic Macquarie Island since its discovery in 1810 has resulted in major changes in the biota. A management programme aims to reduce the numbers of exotic plant and animal species and assist with the recovery of pre‐existing communities and processes. This paper reviews the integrated vertebrate pests management programme on Macquarie Island since 1974 and outlines future management considerations. As part of this programme, the responses of some native and exotic species of vascular flora and vertebrate fauna were monitored following control of European Rabbit (Oryctolagus cuniculus) numbers. Changes in the vegetation recorded over 10 years showed that approximately half of all the vascular species had benefited from rabbit grazing, including several which formed a major part of the rabbit’s diet. After rabbit control, some adversely affected plants responded rapidly to a reduction in grazing pressure while others will require an almost total cessation of grazing in order to re‐establish their former distributions. With the decrease in rabbit numbers it was also necessary to control Feral Cats (Felis catus) due to their increased predation on native burrow‐nesting birds. Feral Cat predation on introduced fauna also increased, one result of which was the eradication from the island of the introduced Weka (Gallirallus australis scotti). Reduced rabbit grazing is leading to re‐establishment of the native Tall Tussock (Poa foliosa) grassland and with it the spread of the introduced Ship Rat (Rattus rattus). This review indicates that an integrated approach to pest management, with monitoring of the responses of both target and non‐target species, is the most effective way to restore pre‐existing communities and processes.Key words grazing pressure, introduced species, predation, recovery, vertebrate pest management.

Managing Vertebrate Pests: Rodents J Caughley, M Bomford, B Parker, R Sinclair, J Griffiths and D Kelly (1998). Bureau of Resource Sciences and Grains Research and Development Corporation: Canberra, c 130 pp. Paperback. Obtainable from, The Publications Officer, Bureau of Resource Sciences, PO Box Ell, Kingston, ACT 2604, Australia; and www.brs.gov.au (ISBN 0642283796). Price AS29.95 (plus tax).

Managing Vertebrate Pests: Rodents J Caughley, M Bomford, B Parker, R Sinclair, J Griffiths and D Kelly (1998). Bureau of Resource Sciences and Grains Research and Development Corporation: Canberra, c 130 pp. Paperback. Obtainable from, The Publications Officer, Bureau of Resource Sciences, PO Box Ell, Kingston, ACT 2604, Australia; and www.brs.gov.au (ISBN 0642283796). Price AS29.95 (plus tax). - Volume 10 Issue 1

On-farm evaluation of the establishment of clonal rubber in multistrata agroforests in Jambi, Indonesia

Perennial tree crops are often grown in complex multistrata systems that incorporate natural vegetation. These systems contribute simultaneously to sustaining rural livelihoods and to the conservation of biodiversity, but their productivity is usually low. Introduction of high yielding germplasm, usually selected in monocultural plantations, is a potential way to increase productivity, but a critical requirement is that such plants can be established in a competitive multispecies environment. The establishment of clonal planting stock in the jungle rubber agroforests of Indonesia was explored through participatory on-farm research. The trial involved four farmers who grew clonal rubber trees in a total of 20 plots, constituting five replicate experimental blocks spread across four farms. Unexpectedly, vertebrate pest damage by monkeys (Presbytis melalophos nobilis) and wild pigs (Sus scrofa) was the most important influence on establishment, explaining almost 70% of the variation in rubber tree growth. The amount of labour invested in weeding was also positively correlated with rubber tree growth. Farmers generally decided to completely cut back vegetation between rows of rubber trees, including potentially valuable trees, rather than weeding within the rows and selectively pruning trees in the inter-row. Farmers thought that the inter-row vegetation would harbour vertebrate pests and compete with the clonal rubber, and they had access to fruits, firewood and other non-timber forest products from other land. Thus, contrary to expectations, when offered clonal germplasm, farmers opted to use plantation monoculture methods to protect what they considered a valuable asset, rather than maintain the traditional multispecies strategy they use with local germplasm.

Bait shyness in possums induced by sublethal doses of cyanide paste bait

Cyanide paste covered in a flour-based lure is commonly used to control populations of the Australian brushtail possum, New Zealand's foremost vertebrate pest. When possums were given sublethal amounts of a standard paste bait, most ate it initially, but 75% refused it 7 days later, having become bait-shy. Most possums were able to discriminate between the toxic paste and the harmless flour-based lure. A less concentrated formof the paste was less effective in killing possums, in contrast toearlier data on the lethality of cyanide. A lower sublethal dose led to a weaker and less persistent bait shyness. Further refinement is therefore required to obtain the optimum concentration that balances reduced shyness and maximum kill. Surviving possums were offered cyanide paste again after 90 and 300 days and only 13 and 17% respectively succumbed, indicating a longlived shyness, as has previously been demonstrated after sublethal poisoning with 1080 baits. The shyness did not generalize towards 1080 paste or pellet baits, or cholecalciferol gel baits. Sustained control of possums is therefore unlikely to be achieved by repeated use of cyanide paste, but changing to other types of toxic bait should provide more effective long-term control.

Vertebrate pest damage to wrapped, baled silage in Ireland

The scale of damage caused by vertebrates to the plastic wrap on baled silage was evaluated on Irish farms. A survey was conducted on 300 farms representative of farming systems and geographical locations throughout Ireland. The scale of damage was classified as farms with 0%, 1-10%, 11-50% or 51-100% of bales with holes in the plastic wrap caused by birds. The proportion of farms within these four classes with damage caused by birds during the short interval between wrapping and removal from the field to storage was 47%, 37%, 15% and 1% of the total, respectively. Correspondingly, during the subsequent storage prior to feedout, bird damage was 37%, 50%, 12%, and 1%. Similarly, the proportions for damage throughout long-term storage due to cats were 71%, 23%, 6% and 0%, while the incidence of damage caused by rats, dogs and farm livestock was comparatively small. The stored bales were fenced against livestock on 86% of farms, while netting, bale painting and other protection methods were used to discourage damage on 2%, 17% and 9% of farms, respectively. The damage caused by birds was more prevalent on farms where the bales were stored on their curved side rather than their flat end, more than twotiers high and in farmyards rather than in fields. Cats damaged the sides and shoulders of the peripheral bales within bale collections, particularly where wrapped bales were stored in the farmyard.

The ecological challenge of immunocontraception: editor's introduction

1. The problems of vertebrate pests are greater now than ever before, with vertebrate control constrained by problems of humaneness, scale and environmental impact. However, immunocontraception involves a conceptually ideal solution. Although not intrinsically novel, its delivery in baits or by a self-spreading vector and its effectiveness in pest control, are now the focus of growing international interest. 2. Major ecological questions correspond to the two forms of delivery: baits and vectors. First, given an effective immunocontraceptive, inserted into a bait and eaten by a pest, would the resulting level of sterilization in the population effectively suppress densities? Secondly, given that the immunocontraceptive agent can be inserted into a microparasitic or macroparasitic infective vector, would the modified vector persist at sufficient prevalence in the host population, and hence suppress densities to the required extent? 3. The papers published in this Special Profile focus on behaviour following sterilization or they model the likely impact of viral-vectored immunocontraception. They highlight advantages and disadvantages of immunocontraception and some general, novel and specific issues. These include the possibility of behaviourally mediated population responses to fertility control; the possible advantages of a mixed baiting and vector strategy; the competitiveness of a modified vector; the appropriateness of immunocontraception for controlling invasive vertebrates on islands; and the need for a ‘pay-off’ methodology for assessing genetic modifications against alternatives. 4. The findings offer significant benefits for management and policy: they will inform decisions on whether to pursue immunocontraception as a control option, and they provide evidence about efficacy and risk in applications to release genetically modified vectors. 5. Although many of the problems in developing immunocontraception technology are biotechnological, questions about the effectiveness of immunocontraceptive pest control are ultimately in the domain of ecologists.

Behavioural Adaptation of Brushtail Possums(Trichosurus Vulpecula)to Captivity

AbstractBrushtail possums,Trichosurus vulpecula, are New Zealand's most serious vertebrate pest, facilitating the spread of bovine tuberculosis to livestock, and causing severe damage to native flora and fauna. Possum control has become a national research priority, involving the use of large numbers of captive possums. Successful adaptation of these animals to captivity is important for the welfare of the possums and for the validity of experimental results. The objective of this study was to determine, by behavioural means, the time individually caged possums required for adaptation to captivity. We used a simple behavioural measure - a possum's daily response to a caregiver at feeding (a feeding test) - to assess changes in the behaviour of possums after arrival in captivity. We also recorded changes in possum body weight throughout this period. Initially most possums ‘avoided’ the caregiver, but within 7 days more than 80 per cent of animals no longer avoided. ‘In den’ and ‘approach’ behaviour rapidly increased for the first 14 days in captivity, after which den use became less common as more possums ‘approached’ the caregiver. By day 29 of captivity, more than 80 per cent of the possums ‘approached’ the caregiver. The possums’ body weight did not change significantly during the first 14 days in captivity, but had increased significantly by day 28, and continued to increase for at least 6 weeks after capture. These data suggest that most possums adapt to captivity within 4 weeks. For the welfare of possums and the reliability of experimental results, we recommend that possums are not used in experiments until at least 4 weeks after capture.

Controlling Vertebrate Pests in Vegetables

Controlling Vertebrate Pests in Vegetables

Molecular ecology and biological control: the mating system of a marsupial pest.

Many studies in molecular ecology have focused on the use of repeat DNA markers to determine the nature of mating systems in a wide variety of animal species. Whilst these studies typically have focused on important issues such as the evolutionary consequences of fitness variation among males, genetic studies of mating systems are potentially also important because they can generate information of significance to wider issues in wildlife management. For example, genetically modified, sexually transmitted viral diseases have been suggested as potential agents for the control of vertebrate pest species. An understanding of the epidemiology of such agents requires an intimate knowledge of the sexual contact rates between individuals of the target species. Here, we report the use of minisatellite DNA profiling to reveal the mating system in two New Zealand populations of the introduced Australian brushtail possum. The brushtail possum is New Zealand's most important mammalian pest and a species for which control by a sexually transmitted immunocontraceptive has been proposed. Encouragingly, we report considerable variation in the reproductive success of males at both study sites, with one male siring offspring from four females in one year (mean no. of offspring/reproductively successful male/year at the two sites is 1.95-2.15), while many sired none. This bias in the pattern of reproductive success among males will probably facilitate the spread of an immunocontraceptive agent and thereby increase the power of this approach to biological control.

A comparative assessment of potential conditioned taste aversion agents for vertebrate management

A conditioned taste aversion (CTA) is acquired through an association between the taste of a food and a feeling of illness experienced after ingestion. It can be induced deliberately by the addition of an undetectable illness-inducing chemical to food. Harnessing the CTA response could provide humane and effective means of controlling vertebrate pest problems. For field use, the ideal illness-inducing chemical should induce a robust CTA after a single oral dose, at which it must cause neither chronic illness nor persistent detrimental effects in the target or any non-target species at risk of exposure; it must also be undetectable and physically stable in the bait substrate. At present, no compound that satisfactorily meets all of these criteria has been identified. 17α ethinyl oestradiol meets most but, as a synthetic oestrogenic hormone, it can affect reproductive processes. The ability of two potentially safe compounds, cinnamamide (160 mg/kg) and thiabendazole (100 and 200 mg/kg) to generate a CTA in the laboratory rat Rattus norvegicus to a novel food was assessed and compared to that of 17α ethinyl oestradiol (4 mg/kg). All compounds induced a CTA after a single dose, which lasted for at least two post-treatment tests, but no CTA was as persistent as that induced by 17α ethinyl oestradiol, which lasted in some rats for >11 post-treatment tests (6 months). Thiabendazole at 200 mg/kg induced the next best CTA, persisting for five post-treatment tests. Cinnamamide and thiabendazole could provide safe alternative CTA agents to 17α ethinyl oestradiol for field use; the use of a second dose of these compounds to improve longevity of the CTA warrants further study.

Lesser-known vertebrate pests of almonds in California

Author(s): Pearson, A. Britt; Gorenzel, W. Paul; Salmon, Terrell P. | Abstract: During a three-year study to assess the effectiveness of broadcast distress calls on American crows (Corvus brachyrhynchos) in almond orchards, we had the opportunity to identify other vertebrate pests, some of which are not well documented. We describe the damage caused by these lesser-known species and in selected cases estimate the crop loss from these other pests in eight orchards in the Central Valley of California. In addition to crows and California ground squirrels (Spermophilus beecheyi), we recorded the presence of seven other vertebrate pests: scrub jays (Aphelocoma coerulescens), yellow-billed magpies (Pica nutalli), common ravens (Corvus corax), deer mice (Peromyscus spp.), western gray squirrels (Sciurus griseus), wild pigs (Sus scrofa), and beaver (Castor canadensis). Jays and magpies were found in six of eight orchards and caused damage of at least $56/ha at one site. Jays and magpies showed a preference for the soft-shelled Nonpariel variety of almond and tended to damage trees throughout the orchards, as opposed to concentrated damage along the edges. Ravens and wild pigs were found only in two Fresno County orchards located next to wildlands of the Coast Range Mountains. We could not specifically identify nor value damage by ravens as they may have reacted to the broadcast crow distress calls and abandoned the treated orchard. Nut loss from pigs amounted to $17/ha. Pig damage could be identified from tracks, broken branches, and the smashed appearance of damage nuts. Deer mice were the most serious pest in the two Fresno County orchards with damage of up to $51/ha. Signs of deer mouse damage included small, fine incisor marks around the edge of the hole in the nut, small shavings from the hull and shell, and a concentration of damaged nuts in the crotch of the tree and around the base of the trunk. Tree squirrels were the most serious pest in one orchard with damage of $46/ha. Tree squirrel damage was concentrated on particular trees in the orchard and damaged nuts were opened in a characteristic manner. Beavers felled almond trees at one orchard located next to a watercourse. We speculate the presence and abundance of a vertebrate pest relate to local habitat conditions, geographic location, the adaptability of species, and the dynamic nature of wildlife populations.

Investigation of sodium monofluoroacetate (1080) bait shyness in wild brushtail possum (Trichosurus vulpecula) populations

Bait shyness is a significant threat to the sustainable control of vertebrate pests. New Zealand's foremost vertebrate pest is the introduced brushtail possum (Trichosurus vulpecula). Bait shyness was identified in two wild possum populations by comparing the consumption of two non-toxic bait types before and after each population was presented with one of the bait types containing the toxin sodium monofluoroacetate (1080). Before poisoning, approximately 60% of total bait consumption was of the type which 1080 was later presented in, whereas after poisoning this bait type made up only 2-4% of total consumption. This shyness persisted for at least 11 weeks in one of the populations. No individual component (bait base, cinnamon lure or green dye) of the toxic bait could be isolated as the primary cue eliciting bait shyness as the response. Possible means of overcoming bait shyness are discussed in light of these findings.

Exposure of non-target wildlife to anticoagulant rodenticides in California

Author(s): Hosea, Robert C. | Abstract: The California Department of Fish and Game collected and analyzed tissue samples from non-target birds and mammals for anticoagulant rodenticides from 1994 through 1999. Many of these animals were collected in recently urbanized areas adjacent to wildlands where they were either found dead or trapped and euthanized as vertebrate pests. The results of the analyses indicate a high frequency of exposure to the anticoagulant rodenticide brodifacoum. Fifty-eight percent of the animals examined had been exposed to brodifacoum, 19% to bromadiolone, 9% to diphacinone, and 8% to chlorophacinone. All of the identified anticoagulants are registered for use to control commensal rodents found in and around structures and are available for sale over-the-counter for homeowner use. Brodifacoum and bromadiolone are registered exclusively for commensal rodent control. This paper assesses the frequency of anticoagulant rodenticide residues in tissues of non-target mammalian and avian wildlife and the possible impacts.

A vision for wildlife management

Author(s): Howard, Walter E. | Abstract: My vision that vertebrate pest control is applied ecology has come a long way since my first field baiting for rats in 1939. Three events are especially important. First, the Vertebrate Pest Conferences were established to provide published information and exchange of views about animal control. Second, on December 19, 1985, the Denver Wildlife Research Center, in the Department of Interior, was transferred to the Department of Agriculture and became the National Wildlife Research Center. Third was when the Wildlife Management Institute finally allowed The Wildlife Society to hold separate annual meetings. This led to the Society recognizing the ecological importance of animal damage control in human-modified environments where the outcome must be managed-not left to nature.

Pocket gopher (Orthogeomys hispidus hispidus) damage in sugarcane fields in the state of Veracruz, Mexico

Information concerning hispid pocket gopher (Orthogeomys hispidus hispidus) damage to sugarcane and the efficacy of sodium monofluroacetate (Compound 1080) treatments for control of this pest were obtained for the State of Veracruz, Mexico. Pocket gophers represent one of the major vertebrate pests based on the severity of economic losses caused to the sugarcane industry in this state. Pocket gophers cause significant damage in over 200,000 ha of sugarcane fields. In this study, a total of 66,560 stalks were examined for damage. Total percentage damaged was 20.67. Economic loss caused by pocket gopher was estimated at approximately $951 in one grower processor’s crop based on the 1998-99 price for raw sugar ($25 dollars/ton). Losses due to this pest species are probably underestimated because many sugarcane industries could not or did not provide loss estimates.