The use of prey hairs found in predator faeces with the purpose of species recognition has been successfully utilized. In this study, a method was developed to discriminate between hairs from aquatic mustelids of Patagonia: the native otters Lontra provocax and L. felina, and the introduced mink Neovison vison. We found that the relationship between the width of the medulla and the total width (medulla+scales) in the zone of maximum width of the hair, allows effectively separating Lontra spp. from Neovison sp. in almost all samples. With these results, we developed a dichotomic guide that allows discriminating 100% of hair at the level of genera, and 58.3% of hair at the level of species within Lontra.
