Otter, Lutra lutra, occurrence in Europe and in France in relation to landscape characteristics

In recent decades, the abundance of otter, Lutra lutra, decreased in many European countries. This study aimed at determining if varying occurrence of otters is related to land features and if this occurs at many spatial scales. Values of landscape features were compared among three categories of otter occurrence, i.e. absent, sporadic and common, for 25 European countries, for 19 regions and 22-40 departments in France. At all scales, significantly higher human and road densities were detected in areas where otters are absent, which illustrates the pervasive impact of human presence on otter population fragmentation. Moreover, particular natural features ('percentage other use' defined as non-agricultural and non-forested) may also limit otter populations at the scale of Europe. Our study failed to detect significant differences in landscapes occupied by common or sporadic otter populations, probably owing to a limited sample size, or to the resilience of otters. The conservation of the European otter in Europe would benefit from an improved list of common large-scale land descriptors, the recognition of large gaps of naturally unsuitable habitats, and the development of international large-scale conservation studies to support existing regional otter conservation efforts.