Sea Otters (Enhydra lutris L.) of Bering Island, the Commander Islands: Age and Sex Composition of Dead Animals and Spatial Distribution

Animal censuses and assessment of mortality in the sea otter subpopulation of Bering Island (the Commander Islands) have shown that indices of seasonal mortality may be used as a criterion for estimating well-being of this animal group. In 1999, the subpopulation of Bering Island entered a phase of stabilization of its spatial, age, and sex structure, with the stabilization process proper taking approximately three years after a peak of mortality. Mortality in the course of this process proved to be relatively high in age groups older than eight years but insignificant among middle-aged reproductive animals. As the age and sex structure of the insular group varies during the year and in different coastal areas, the data obtained by collecting dead animals cannot be used for estimating the structure of the whole population.