Local habitat preferences of a semi-aquatic mammal, the Pyrenean desman Galemys pyrenaicus

To date, the large-scale distribution of the endangered Pyrenean desman, Galemys pyrenaicus, has been related to various abiotic factors (e.g. riverbed and riverbank characteristics, hydrology, topography, climate). However, none could fully explain the recent observed range contraction of the species, suggesting the influence of other drivers. In this study, the potential effect of some unexplored variables on the Pyrenean desman presence was investigated at the local scale (i.e. stream reaches) in the French Pyrenees. They described not only the riverbed, riverbanks, water chemistry, topography and pedology but also the presence of potential interacting species. Generalised linear models were implemented to select the best drivers of the Pyrenean desman presence. Our results stressed the relevance of considering human impacts at the riverbed scale, river narrowing and water chemistry to explain the local distribution of the Pyrenean desman. The presence of two potential competitors, the Eurasian water shrew Neomys fodiens and the dipper Cinclus cinclus, was also highly correlated to the species presence in stream reaches. This suggests that all three species may use the same resources within streams, which could be a potential source of competitive interactions. This study not only highlights the importance of maintaining the riverbed integrity for the Pyrenean desman but also stresses the need to assess the extent to which biotic interactions may affect its distribution in order to understand its current decline.