Survey and Habitat Evaluation for a Peripheral Population of the Eurasian Otter in Italy

The Eurasian otter has declined sharply in Italy in recent decades, now surviving only in the southern regions. Knowledge of the species’ range and environmental factors affecting its distribution is limited. From 2000 to 2002, we conducted a field survey in the Molise region of Italy, an area of formerly known to be occupied by the Eurasian otter. The survey followed the “standard method” for monitoring otter presence used in other European countries. The area was searched for sign of otter, with 6 habitat structure parameters recorded at the 191 sites. Multivariate ordination and hierarchic classification were used to find environmental similarities between sites where otters were present or absent. Otter sign were detected at 22 sites, concentrated in the Volturno and Biferno River basins. Three habitat suitability classes were distinguished through hierarchic clusters derived from multivariate ordination, which are mostly influenced by elevation and vegetation cover on riverbanks. Through the analysis of the distribution of suitable sites in the study area we were able to define sites unoccupied by otters in the region that offer the best opportunity for recolonization.