Non-invasive methods for genotyping of stoats (Mustela erminea) in New Zealand: potential for field applications

Stoats (Mustela erminea) are a significant pest in New Zealand. A critical aspect of their management is the ability to identify individuals in order to estimate abundance or to determine the origin of residual animals after control, particularly as the trap-shy nature of stoats reduces the utility of trapping to gain this information. We investigated non-invasive ‘capture’ methods as an alternative to live-trapping or removal methods for estimating stoat abundance. First we determined whether sufficient variability exists at six microsatellite DNA loci to reliably identify individuals in the potentially bottlenecked, introduced stoat populations of New Zealand. In December 2001 we conducted a 7-night pilot field experiment using a modified hair-tube design, where we obtained a total of 64 hair samples. Sufficient DNA was extracted from 3–6 hair follicles to genotype a total of 51 samples. DNA quality declined if samples were left in the field for several nights before being collected, and daily checks proved best for maximising the quality of DNA obtained, while minimising the risk of multiple ‘captures’ of stoats. Conclusions were that non-invasive molecular sampling is likely to be a viable technique for estimating population density of stoats in New Zealand beech forest but that additional variable loci are required.