Aerial baiting and wild dog mortality in south-eastern Australia

Abstract ContextWild dogs, including dingoes and dingo cross-breeds, are vertebrate pests when they cause financial losses and emotional costs by harming livestock or pets, threaten human safety or endanger native fauna. Tools for lethal management of these animals currently include aerial baiting with poisoned baits. In New South Wales (NSW), Australia, aerial baiting was previously permitted at a rate of 40 baits km−1 but a maximum rate of 10 baits km−1 was subsequently prescribed by the Australian Pesticides and Veterinary Medicines Authority. The efficacy of these baiting rates has not been quantified in eastern Australia, undermining the value of the policy and rendering adaptive management efforts difficult, at best. AimTo quantify the mortality rate of wild dogs exposed to aerial baiting at historic and currently approved rates, i.e. 40 baits per kilometre and 10 baits per kilometre, respectively. MethodsWild dog mortality rates were measured at sites in mesic north-eastern NSW, where aerial baiting was applied to control wild dogs and contrasted with sites and individuals where no baiting was undertaken. In total, 132 wild dogs were trapped and fitted with GPS-VHF telemetry collars before annual aerial baiting programs. Collars were used to locate animals after aerial baiting and to determine the fates of individuals. Key results90.6% of collared wild dogs exposed to aerial baiting at 40 baits km−1 died, whereas only 55.3% of those exposed to 10 baits km−1 died (Welsh’s t=4.478, P=0.004, v=6.95). All wild dogs that were not exposed to toxic baits survived during the same periods. ConclusionManagers using aerial baiting to maximise wild dog mortality in mesic south-eastern Australia should use 40 baits km−1 rather than 10 baits km−1. ImplicationsWild dog population reduction for mitigation of livestock and faunal predation requires the application of efficacious control. The currently prescribed maximum aerial baiting rate of 10 baits km−1 is inadequate for controlling wild dog populations in mesic forest environments in NSW.

Canine rabies in Australia: a review of preparedness and research needs

Australia is unique as a populated continent in that canine rabies is exotic, with only one likely incursion in 1867. This is despite the presence of a widespread free-ranging dog population, which includes the naturalized dingo, feral domestic dogs and dingo-dog cross-breeds. To Australia's immediate north, rabies has recently spread within the Indonesian archipelago, with outbreaks occurring in historically free islands to the east including Bali, Flores, Ambon and the Tanimbar Islands. Australia depends on strict quarantine protocols to prevent importation of a rabid animal, but the risk of illegal animal movements by fishing and recreational vessels circumventing quarantine remains. Predicting where rabies will enter Australia is important, but understanding dog population dynamics and interactions, including contact rates in and around human populations, is essential for rabies preparedness. The interactions among and between Australia's large populations of wild, free-roaming and restrained domestic dogs require quantification for rabies incursions to be detected and controlled. The imminent risk of rabies breaching Australian borders makes the development of disease spread models that will assist in the deployment of cost-effective surveillance, improve preventive strategies and guide disease management protocols vitally important. Here, we critically review Australia's preparedness for rabies, discuss prevailing assumptions and models, identify knowledge deficits in free-roaming dog ecology relating to rabies maintenance and speculate on the likely consequences of endemic rabies for Australia.

Reintroducing the dingo: the risk of dingo predation to threatened vertebrates of western New South Wales

Context The reintroduction of dingoes into sheep-grazing areas south-east of the dingo barrier fence has been suggested as a mechanism to suppress fox and feral-cat impacts. Using the Western Division of New South Wales as a case study, Dickman et al. (2009) recently assessed the risk of fox and cat predation to extant threatened species and concluded that reintroducing dingoes into the area would have positive effects for most of the threatened vertebrates there, aiding their recovery through trophic cascade effects. However, they did not formally assess the risk of dingo predation to the same threatened species. Aims To assess the risk of dingo predation to the extant and locally extinct threatened vertebrates of western New South Wales using methods amenable to comparison with Dickman et al. (2009). Methods The predation-risk assessment method used in Dickman et al. (2009) for foxes and cats was applied here to dingoes, with minor modification to accommodate the dietary differences of dingoes. This method is based on six independent biological attributes, primarily reflective of potential vulnerability characteristics of the prey. Individual-attribute scores were used to derive an overall risk score. Key results Up to 75 (94%) of the 80 extant species were predicted to be at risk of dingo predation (71% at high risk) regardless of any effect dingoes might have on foxes or cats. Up to 17 of the 21 (81%) locally extinct species were predicted to be at high risk of dingo predation using this approach. The re-establishment of even low-density dingo populations may have negative effects on at least 22% of extant threatened vertebrates. Conclusions The generic risk-assessment method was insensitive, and experienced difficulty in describing the true nature of canid predation risk. Despite this weakness, however, it is clear that several threatened vertebrates are susceptible to dingo predation. Prior to the re-establishment of dingoes, we recommend that dingo predation risks to all vertebrates (threatened or otherwise) be assessed using more sensitive and descriptive techniques, and we strongly caution against the positive management of dingoes under current ecological conditions. Implications The results of this study imply that dingoes present similar levels of direct risk to threatened species as foxes and feral cats, and dingo predation of threatened species should be formally considered in any proposal encouraging dingo populations in western New South Wales.

A strategic approach to mitigating the impacts of wild canids: proposed activities of the Invasive Animals Cooperative Research Centre

Wild canids (wild dogs and European red foxes) cause substantial losses to Australian livestock industries and environmental values. Both species are actively managed as pests to livestock production. Contemporaneously, the dingo proportion of the wild dog population, being considered native, is protected in areas designated for wildlife conservation. Wild dogs particularly affect sheep and goat production because of the behavioural responses of domestic sheep and goats to attack, and the flexible hunting tactics of wild dogs. Predation of calves, although less common, is now more economically important because of recent changes in commodity prices. Although sometimes affecting lambing and kidding rates, foxes cause fewer problems to livestock producers but have substantial impacts on environmental values, affecting the survival of small to medium-sized native fauna and affecting plant biodiversity by spreading weeds. Canid management in Australia relies heavily on the use of compound 1080-poisoned baits that can be applied aerially or by ground. Exclusion fencing, trapping, shooting, livestock-guarding animals and predator calling with shooting are also used. The new Invasive Animals Cooperative Research Centre has 40 partners representing private and public land managers, universities, and training, research and development organisations. One of the major objectives of the new IACRC is to apply a strategic approach in order to reduce the impacts of wild canids on agricultural and environmental values in Australia by 10%. In this paper, the impacts, ecology and management of wild canids in Australia are briefly reviewed and the first cooperative projects that will address IACRC objectives for improving wild dog management are outlined.

The impact of rabbits on a grazing system in eastern New South Wales.1. Ground cover and pastures

Although there have been a number of studies that have examined the effects of rabbits on pasture, the relationship between rabbit density and pasture degradation caused by rabbits has never been quantified. An experiment was conducted at Cowra, New South Wales, from October 1984 to October 1987, to determine the impact various densities of rabbits have on pasture composition, indices of pasture biomass and ground cover. Using plots set stocked with the equivalent of 8 sheep/ha (the district average) and 4 densities of rabbits as treatments, 0,�24, 48 and 72 rabbits/ha, the consequences of rabbit grazing were investigated.Pasture composition changed with season, year and rabbit density. Cumulative effects were also evident. Rabbits severely depleted improved pastures of legumes (subterranean clover particularly), with grass cover increasing proportionate to rabbit density. In the final year of the experiment, the rabbit-free treatment had 31% legumes and 25.2% grasses, whereas the highest rabbit density treatment had 6.2% legumes and 47.4% grasses. Indices of pasture biomass were highest in the zero rabbits/ha treatment and lowest in the 72 rabbits/ha treatment. More bare soil was exposed in the highest rabbit density treatment. Once seasonal and year effects were accounted for, the relationship between rabbit density and percentage damage was positive.

Ground-Placed Baits for the Control of Wild Dogs: Evaluation of a Replacement-Baiting Strategy in North-Eastern New South Wales

Abundance indices for wild dogs (Canis familiaris familiaris and C. familiaris dingo) were calculated from their visitation to stations containing non-toxic baits before and after a replacement-baiting programme (conducted in January-February 1993). The programme, where 1080 (sodium fluoroacetate)-impregnated baits removed by target animals were replaced each day, achieved a mean reduction of 76.1% in the index of dog abundance. The replacement-baiting strategy removed all resident animals that would accept baits and the probable reductions in the populations of dogs were greater than the reductions reported in previous studies. The indices of the abundance of sympatric red foxes (Vulpes vulpes) were also reduced (90.8%) by the replacement-baiting programme. Minimum numbers of dogs and foxes using roads and tracks in the study area were estimated by index-manipulation-index methodology. The risk of this replacement-baiting programme to populations of non-target animals was insubstantial. The effects of the manipulation of canid populations on the management of populations of non-target animals are discussed.

Indices for Measuring the Efficacy of Aerial Baiting for Wild Dog Control in North-Eastern New South Wales

The efficacy of aerial baiting with 1080 poison (sodium fluoroacetate) for the control of wild dogs (Canis familiaris familiaris and C. familiaris dingo) in the temperate rangelands of north-eastern New South Wales was studied. In each year from 1991 to 1993, 2 indices of the abundance of dogs, one a raw count of sets of footprints per km of transect (SF) and the other an ln-transformed frequency corrected for sightability of signs (CI), were used to quantify the changes in abundance caused by aerial baiting. Abundance of dogs at a nil-treatment site was estimated concurrently. The SF index found the 1991 baiting to be efficacious. Both measures of abundance showed baiting to be efficacious in 1992 and 1993. Reductions of 66.3-84.5% in the abundance of dogs at the treatment site were found for the CI measure. The SF measure displayed abundance changes of 76.1-91.1%. The indices of abundance measured prior to the annual baiting in 1992 and 1993 were similar, indicating that populations returned to their initial abundance within 1 year.

Evaluation of the Efficacy of 1080 Poisoning of Red Foxes Using Visitation to Non-Toxic Baits as an Index of Fox Abundance

Visits of foxes to non-toxic baits were used to derive fox abundance indices at 4 sites in north-eastern New South Wales. A 1080 (sodium fluoracetate) poisoning campaign resulted in a mean population reduction of 69.5% (s.d. = 4.9). Fox densities before baiting, calculated using the index-removal-index method, ranged from 4.55 to 7.16 foxes km-2. Visitation to non-toxic baits is recommended as a reliable estimate of relative density. This study investigated the efficacy of 1080 baiting as a technique for the control of foxes in tableland environments. The implications of the estimated fox densities and population reductions on fox control in agricultural areas and in the context of rabies are discussed.

The Cost of Aerial Baiting for Wild Dog Management in North-Eastern New South Wales

Aerial baitjng for the management of wild dogs in north-eastern New South Wales is carried out in nine Rural Lands Protection Board districts covering coastal and tablelands environments. A survey of participants in the 1988 aerial baiting programme costed the total operation at $106,152. Labour ($36,418) and helicopter hiring charges ($35,693) accounted for over 70 per cent of the costs borne by local and regional control authorities. A total of 24,285 kg of meat (approx. 105,500 baits) valued at $21,018 was used. The average cost of the programme was $4.21 per kg of bait used. Total baiting costs can be accurately predicted from bait quantity. The cost, to individual producers, of aerial baiting for wild dogs, when compared with expected livestock losses without this form of management, suggests that aerial baiting is cost-beneficial.

Temporal Decline of 1080 Within Meat Baits Used for Control of Wild Dogs in New South Wales

Short- and long-term trials were conducted to determine the rate of decline of 1080 (sodium fluoroacetate) in meat baits used for poisoning wild dogs. Baits were injected with 0.2 ml of standard 1080 solution (nominal dose of 6.00 mg of pure 1080 per bait) and placed in the field. In the long-term trial, 10 baits were collected at 7 intervals between 3 h and 226 days, and analysed for residual 1080 by liquid chromatography. The recoverable 1080 content declined greatly over the first 48 days, although at 226 days all 10 baits retained some 1080. By 42.4 days the mean residual level of 1080 in the baits was predicted to be less than the theoretical LD99 for wild dogs. At the time of distribution, baits contained less than the LD50 for an average-sized eastern quoll. The LD99 for domestic cattle-dogs was predicted to be still present in baits at 72.9 days. Loss of 1080 from these baits was not correlated with rainfall, temperature or humidity. In the short-term trial, 10 baits were collected at 11 intervals up to 200 h. The recoverable 1080 content decreased by 3.09 mg (61% of the injected dose) within the first hour after injection and declined to a low of 2.70 mg at hour 50. The level of recovered 1080 then rose to 73% of the injected dose at hour 150.

Predation of livestock by wild dogs in eastern New South Wales

A monthly survey involving officers from eastern New South Wales Pastures Protection Boards was conducted over four years from 1982 to 1985. Information was collected on the number and type of livestock attacked within each board district, sightings of wild dogs, the number of wild dogs kiied, the method by which they were kiied and the locations at which the observations occurred. A total of 25,644 livestock animals were reported killed or wounded from four regions; the North-East Coastal Region, the North-East Tablelands Region, the Central-East Region and South-East Region. Sheep were the most commonly attacked domestic animals followed by cattle and goats. Regional differences were apparent in the type of livestock killed and seasonal patterns of predation were evident. We recommend that annual control programmes be brought forward from June/July to late April in order to precede predation peaks.

Effect of Presentation on the Attractiveness and Palatability to Wild Dogs and Other Wildlife of 2 Unpoisoned Wild-Dog Bait Types

Factory-prepared beef crackle cubes and fresh meat baits are routinely used with the poison 1080 to prevent or reduce predation by wild dogs, Canis familiaris. Four field trials totalling 674 bait nights per bait type were conducted in southern Queensland to assess the relative attractiveness and palatability of the two baits to wild dogs and non-target animals. Buried meat and surface-laid meat baits were also compared to assess the effect that bait presentation can have on control programme efficiency and non-target hazard. Fresh meat was found to be significantly more palatable to wild dogs than factory baits. Factory baits, despite being equally attractive to wild dogs as fresh meat, had significantly more visits by wild dogs where baits were not eaten. Fresh meat was significantly more attractive and palatable to non-target species than factory baits. Buried baits were equally attractive and palatable to wild dogs compared with surface-laid meat baits, yet had greatly reduced non-target bait take. The significance of the results is discussed with regard to the potential 1080 hazard to birds and reptiles (which removed 28% and 10% of baits, respectively) and the influence that non-target removal of baits may have on the efficiency and design of wild-dog control programmes. Extra keywords: Compound 1080, poison, SEA, sodium fluoroacetate.

Flying-fox (Chiroptera: Pteropodidae) on the north coast of New South Wales: damage to stonefruit crops and control methods

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