Leukocyte formula of the Walser’s Viper (Vipera walser)

Vipera walser is a recently assessed species of North-Western Italian Alps, that has been regarded as an isolated population of V. berus until 2016, when it has been identified as a separate taxonomical unit according to molecular markers. Due to its restricted and fragmented range and the potential threat of climate change in mountain systems, it complies with the IUCN criteria to be classified as EN. In order to investigate, in part, the health status of this taxon, we have performed blood smears to describe whether a haematological parameter such as leukocytes is consistent with those of more widespread viperids of the Italian peninsula. Overall, we sampled 20 Walser’s Vipers across the species range and characterised leukocyte formula. We found that lymphocytes were the most common (~70% of total leukocytes). Eosinophils and heterophils were less abundant, while neutrophils and monocytes are the least represented. Our data is in accordance with that of other European viperids.