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Project Name |
Modelling the population dynamics of hedgehogs on the Outer Hebrides with a view towards eradication |
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Dates |
1/07/2007 - 30/08/2009 |
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Project Collaborators |
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Funders |
Scottish Natural Heritage |
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Project Description
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An individual-based simulation model of hedgehog populations was developed to investigate the predicted effect of methods to eradicate or control this invasive mammal species. The spatially-explicit approach adopted was able to recapitulate the known spread of hedgehogs through the three main Outer Hebridean Islands and was considered suitable for the simulation of control efforts. A sensitivity analysis of the model revealed that the parameters of breeding success of multiparous females, mortality of juvenile females in the non-breeding season, and mortality of adult females in the breeding season were the most important drivers of the simulated population. A greater focus on these parameters in future research efforts will improve the confidence in the predictions of this model. The simulation of control efforts indicated that eradication of hedgehogs in the Hebrides is unrealistic in the short term (10 years) with current trapping levels; however, current effort should be capable of reducing the population, and has probably reduced the range expansion of the population. Current efforts are predicted to be able to reduce or eradicate hedgehogs where they are performed, and thus would protect areas of particular concern with respect to ground-nesting birds. The model also predicts that this level of control requires yearly effort ad inifinitum, since the hedgehog population in untrapped areas continues to increase. More effective control could be realistically achieved by a mobile control method (such as lamping), and one which concentrates on the removal of individuals from all habitats. The current model reduces control to three driving variables (intensity, mobility and efficiency), and this approach lends itself to the investigation of the efficacy of any control methods which can be described in these terms. The model can be used to explore the effort and cost required to achieve complete eradication of hedgehogs on North Uist, and plan a strategy for the systematic control of hedgehogs on Benbecula and South Uist. However, such methods prove complex, since they also depend on social, temporal, and spatial factors, such as access at different times of year and the consent of the local community. A Decision Support Tool was developed as an extension to the original project. This tool summarised the outputs of the model using Generalised Linear Modelling, and permitted managers to plan eradication zones and trapper effort to optimise eradication efforts. |
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