Measuring stoat (Mustela erminea) and ship rat (Rattus rattus) capture success against micro-habitat factors

The influence of micro-habitat on stoat (Mustela erminea) and rat (Rattus rattus) capture success was explored using trapping data collected from large scale predator control operations at the Okarito and Moehau Kiwi (Apteryx spp.) sanctuaries. Generalised linear models were used to explore the relationship between micro-habitat predictors and predator kill trapping records from individual trap sites. Our results suggest that micro-habitat information can provide useful predictors of rat and stoat capture success. Evidence from other studies and the current trapping regime provided a reasonable explanation for why some micro-habitat variables were or were not significantly associated with capture success. However, model complexity and the subjective trapping layout made interpretation of some variables challenging. Model results varied considerably between sanctuaries for the same species. We recommend reducing the number of micro-habitat variables to better reflect biological mechanisms; where possible recording variables continuously; nesting small-scale spatial variables within large-scale spatial variables; and standardising micro-habitat variables to allow model comparisons between trapping areas. Future research also needs to disentangle the effects of trapping edge and biased topographical layout from trap capture success. Good study design would resolve many of these problems. Results should help generate new and/or prioritise existing hypotheses for more focused research in the future.