Individual sexing and genotyping from blood spots on the snow: a reliable source of DNA for non-invasive genetic surveys

Non-invasive genotyping is an effective tool to study natural populations of elusive and endangered carnivores. This study demonstrates the usefulness of blood spots collected on the snow as source of DNA for individual sexing and genotyping. Thirty-seven samples, collected during snow-tracking of wild wolves (Canis lupus), were analysed by a set of 10 canine microsatellites and tested for sex. From 26 fully amplifiable DNA samples, 16 different wolf multilocus genotypes were obtained. A low (1%) genotyping error rate was detected. Body wounds and vaginal blood seepage of she-wolves in proestrus may account for the origin of such samples. As consequence, sex of genotyped individuals is biased in favour of females. Advantages and drawbacks associated to the their collection and analysis are discussed. Their lower frequency along trails in snow respect to other samples is balanced by the higher reliability of their analysis. The collection and analysis of such blood samples during non-invasive winter surveys of endangered carnivores is therefore recommended.