Target-specific vertebrate pest control in complex faunal communities: feral pig baiting in the Wet Tropics of Queensland, Australia

Andrew Bengsen (2010). Target-specific vertebrate pest control in complex faunal communities: feral pig baiting in the Wet Tropics of Queensland, Australia PhD Thesis, School of Animal Studies, The University of Queensland.

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Author Andrew Bengsen
Thesis Title Target-specific vertebrate pest control in complex faunal communities: feral pig baiting in the Wet Tropics of Queensland, Australia
School, Centre or Institute School of Animal Studies
Institution The University of Queensland
Publication date 2010-07
Thesis type PhD Thesis
Supervisor Dr Luke Leung
A/Prof Steven J Lapidge
Prof Iain J Gordon
Total pages 122
Total black and white pages 122
Subjects 07 Agricultural and Veterinary Sciences
Abstract/Summary Worldwide, lethal control is an important means of mitigating the adverse impacts of vertebrate pests. The range of lethal control tools available for any given situation is generally limited by a range of constraints, including the risk of non-target species being harmed by pest control activities. Non-target impacts are particularly problematic in complex faunal communities, where the target pest shares a substantial degree of functional similarity, such as dietary preferences, with one or more non-target species. In these situations, it can be difficult to identify differences between pest and non-target species that can be exploited to develop target-specific pest control tools. Here, I present a methodological framework that can assist in the identification of exploitable differences between pest and non-target species. The model consists of five steps: 1) selection of the most appropriate basis for control; 2) identification of opportunities to prevent non-target species from interacting with control activities; 3) classification of non-target species by dissimilarity to the target pest; 4) use of a recognition systems approach to identify further differences between pests and non-target species; and, 5) experimental evaluation of prototype control tools. The framework is demonstrated by using it to develop target-specific methods for poison baiting of feral pig (Sus scrofa) populations in the tropical rainforests of the Daintree region, in north-eastern Australia’s Wet Tropics World Heritage Area. Application of the framework identified several bait design features that could potentially prevent or substantially reduce the incidence of bait consumption by specific groups of non-target species, without inhibiting bait consumption by feral pigs. These bait design features were systematically evaluated in a series of experiments between 2007 and 2009. The first experiment evaluated design features identified in the third step of the framework, which sought to test simple measures to reduce bait consumption by the majority of non-target species. All known resident species were dichotomously classified according to dissimilarities to the feral pig in aspects of their behaviour that related to the selection of food or foraging habitat. Consistent with predictions generated using this method, the monitoring of animal-bait interactions at 18 sites showed that nocturnal bait distribution prevented bait-take by diurnal foragers, and shallow burial substantially reduced bait-take by non-fossorial species. The ability of bait containing both animal and vegetable material to prevent bait selection by dietary specialists could not be tested because these species failed to take either omnivore or vegetarian control baits. Application of the fourth step of the framework indicated that bait consumption by feral pigs and non-target species to which pigs were most similar should vary seasonally. The second experiment tested whether differences in seasonal variation in bait encounter and acceptability between pigs and non-target species could be exploited to identify optimal seasonal conditions for baiting. Animal-bait interactions were monitored at six sites bi-monthly for 18 months, and analysed in relation to temporal change in the availability of alternative foods for small mammals, the physiological condition of feral pigs, and variability in the activity levels of small mammals and pigs. This required the development of a novel camera-trapping method to index the relative abundance of feral pigs. The seasonal study was hampered by poor bait encounter and consumption by feral pigs, and did not identify exploitable seasonal differences in bait consumption by pigs and non-targets. However, observations that the number of small mammals that encountered baits was correlated with the number of small mammals trapped at a site, and that the physiological condition of pigs was inversely related to the preceding two months’ rainfall, suggested that seasonal influences might be important if a bait that was more attractive to pigs could be developed. The third experiment also evaluated a bait design feature identified using the fourth step of the framework. Detailed interspecific comparisons of the behaviour of small mammals and feral pigs indicated that small nocturnal mammals should be deterred from foraging at sites that were augmented with cues indicating an enhanced risk of predation for these species, whereas feral pigs should not. Animal-feed interactions were monitored using giving-up-densities at depletable feeding stations, and remote cameras at pig baiting sites. When applied to an attractive bait, the illumination of baiting sites consistently reduced the foraging intensity of small mammals, but did not inhibit bait encounter or consumption by feral pigs. Auditory repellents were consistently ineffective. The preceding studies showed that manufactured baits were often removed by dingoes, whereas bait encounter and consumption by feral pigs was generally low. The fourth experiment aimed to overcome these problems by developing a bait substrate that was attractive and acceptable to pigs, but not available to dingoes or other non-targets. Using the fourth step of the methodological framework, it was predicted that pigs should find a starch-rich bait acceptable, whereas dingoes should not, and that a lightweight cover could prevent small-bodied omnivores from accessing baits. Remote cameras and sandplots were used to monitor interactions between animals and three bait treatments: covered manufactured baits, covered corn and copra meal bait, and uncovered corn and copra meal bait. Results showed that feral pigs found the corn and copra meal bait much more acceptable than manufactured baits; dingoes did not find the corn bait acceptable; and that small mammals did not access covered baits when uncovered bait was available. These studies have shown that poison baiting for feral pig control in the Wet Tropics World Heritage Area can be conducted in a manner that does not pose a high risk to non-target species. Until now, poison baiting has not generally been available for pig control in the region because of its potential non-target impacts. Further studies should assess the effects of poison baiting on populations of pigs and non-target species, as well as the damage caused by pigs. More generally, the studies reported in this thesis have highlighted the difficulties of developing target-specific pest control tools for use in complex faunal communities, and have demonstrated a useful methodological framework to overcome this problem. The framework should also have applications in areas other than lethal pest control, such as the development of pharmaceutical baits for wildlife populations.
Keyword baiting
feral animals
Feral pig
non-target species
Sus scrofa
vertebrate pest control
Wet Tropics World Heritage Area
Additional Notes none

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Created: Fri, 19 Nov 2010, 08:46:50 EST by Mr Andrew Bengsen on behalf of Library - Information Access Service