An Analysis of San Juan River Otter (Lontra canadensis) Diets

Abstract

This study analyzes the diets of Lontra canadensis populations on San Juan Island, Washington. It tests the hypothesis that the majority of river otter diets, in the populations studied, is composed of fish and crustacean species. Sixty scat samples were collected from two latrine sites in differing environments, and sorted through for remaining hard prey fragments. Fish and crustaceans were the overwhelming majority of otter prey found at each site. However, crustaceans made up a greater proportion of the diets of L. canadensis foraging in the sheltered harbor site than those hunting at the wave-exposed point. This study acts as a starting point for future river otter diet analysis in the San Juan Archipelago, an area not previously studied.