Activity Budgets and Prey Consumption of Sea Otters (<I>Enhydra lutris kenyoni</I>) in Washington

Abstract

Northern sea otters (Enhydra lutris kenyoni) were extirpated from the Washington coast in the early 1900s. Reintroductions of sea otters from Amchitka Island, Alaska, occurred in 1969 and 1970. By 2005, 814 sea otters occupied a range from Destruction Island north to Makah Bay. The focus of this study was to investigate diurnal activity budgets and variability in prey consumption at four locations in the current Washington sea otter range to test hypotheses concerning population growth potential and local impact of sea otters on prey availability. Overall, sea otters primarily spent their daylight hours resting (62.3%), grooming (19.7%), and feeding (7.6%). These activities varied by location. Diet consisted predominantly of crabs, clams, and sea stars. In each study area, one main prey item comprised 33.4 to 64.4% of the total prey consumed; however, the main prey item differed among locations. Of the foraging dives observed, 81.4% were successful. Average dive duration was 35.6 s; however, this varied among locations as well. The study locations were utilized differently—some as resting sites and others as feeding sites. The low diurnal feeding activity found in this study indicates that food availability was high, suggesting that this Washington population of sea otters is currently below equilibrium density.