Modelling habitat preferences of feral pigs for rooting in lowland rainforest

Elledge, Amanda E., McAlpine, Clive M., Murray, Peter J. and Gordon, Iain J. (2013) Modelling habitat preferences of feral pigs for rooting in lowland rainforest. Biological Invasions, 15 7: 1523-1535. doi:10.1007/s10530-012-0387-6

Author Elledge, Amanda E.
McAlpine, Clive M.
Murray, Peter J.
Gordon, Iain J.
Title Modelling habitat preferences of feral pigs for rooting in lowland rainforest
Journal name Biological Invasions   Check publisher's open access policy
ISSN 1387-3547
Publication date 2013-07-01
Year available 2012
Sub-type Article (original research)
DOI 10.1007/s10530-012-0387-6
Open Access Status DOI
Volume 15
Issue 7
Start page 1523
End page 1535
Total pages 13
Place of publication Dordrecht, Netherlands
Publisher Springer
Language eng
Abstract Invasive wildlife often causes serious damage to the economy and agriculture as well as environmental, human and animal health. Habitat models can fill knowledge gaps about species distributions and assist planning to mitigate impacts. Yet, model accuracy and utility may be compromised by small study areas and limited integration of species ecology or temporal variability. Here we modelled seasonal habitat suitability for wild pigs, a widespread and harmful invader, in northern Australia. We developed a resource-based, spatially-explicit and regional-scale approach using Bayesian networks and spatial pattern suitability analysis. We integrated important ecological factors such as variability in environmental conditions, breeding requirements and home range movements. The habitat model was parameterized during a structured, iterative expert elicitation process and applied to a wet season and a dry season scenario. Model performance and uncertainty was evaluated against independent distributional data sets. Validation results showed that an expert-averaged model accurately predicted empirical wild pig presences in northern Australia for both seasonal scenarios. Model uncertainty was largely associated with different expert assumptions about wild pigs' resource-seeking home range movements. Habitat suitability varied considerably between seasons, retracting to resource-abundant rainforest, wetland and agricultural refuge areas during the dry season and expanding widely into surrounding grassland floodplains, savanna woodlands and coastal shrubs during the wet season. Overall, our model suggested that suitable wild pig habitat is less widely available in northern Australia than previously thought. Mapped results may be used to quantify impacts, assess risks, justify management investments and target control activities. Our methods are applicable to other wide-ranging species, especially in data-poor situations.
Formatted abstract
Feral pigs (Sus scrofa) occupy many different habitats worldwide. Their rooting foraging behaviour poses a serious threat to biodiversity as the resulting soil disturbance alters ecosystem structure and function. Understanding what characteristics are important in selecting rooting locations can be used to predict the impact of pigs on ecosystems. We investigated patch selection for rooting by feral pigs at two spatial scales: (1) habitat variables at a site level, and (2) dependency between observations in a spatial context. Seasonal influences on the modelled environmental variables were also examined. We applied a generalised linear modelling approach and model-averaging to explain the relative importance of variables, as measured by the standardised parameter estimates and unconditional variance. Soil texture, rock cover, soil compaction and sand texture were important explanatory variables in the presence of pig rooting. Soil compaction and distance to roads had a negative influence. The highest ranking model included seven explanatory variables with a 41 % chance that this is the Kullback-Leibler best model. Six of the 128 candidate models were in the 95 % confidence set indicating low model uncertainty. Although no differences in pig rootings were detected between seasons, most rooting (65.7 %) occurred during the dry season with soil and sand texture having the strongest effect. This study highlights how pig control programmes can focus limited resources on either the strategic positioning of control devices (e.g., traps and baits) to either reduce the number of pigs or help prioritise habitats of high conservation value for protection (e.g., exclusion fencing).
Keyword Foraging
Generalised linear modelling
Habitat preferences
Model averaging
Sus scrofa
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published online: 13 December 2012.

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Created: Mon, 08 Apr 2013, 22:42:48 EST by Peter Murray on behalf of School of Agriculture and Food Sciences