Diet diversity and breeding of top predators are determined by habitat stability and structure: a case study with the Eurasian otter (Lutra lutra L.)

A study on Eurasian otter was conducted in order to establish if feeding ecology and breeding of this European freshwater top predator were affected by the habitat complexity or stability. The work was based on the comparison of contrasting environmental settings. Significant gradients were found for otter diet parameters and breeding, both also changing according to habitat gradient patterns (water capacity and permanence during droughts, habitat stability, and habitat complexity). The otter diet was less diverse in the most stable (and complex) habitats, eating more fish. Otters also breed more regularly in such more stable courses, with more suitable fish availability. The step toward lower habitat stability can put otters in a less advantageous position in front of generalist predators, foraging more frequently outside or in the edge of aquatic ecosystems. Implications for otters and other similar top predator's conservation are discussed.