Sea otter population collapse in southwest Alaska: assessing ecological covariates, consequences, and causal factors

Sea otter (Enhydra lutris) populations in southwest Alaska declined substantially between about 1990 and the most recent set of surveys 2015. Here we report changes distribution abundance sea otters, covarying patterns reproduction, mortality, body size condition, diet foraging behavior, food availability, health profiles, exposure to environmental contaminants over this 25-yr period. The population decline, which resulted densities on order 5% carrying capacity, ranged from Attu Island west Castle Cape (on south side Peninsula) east. Remaining otters moved closer shore into shallow, protected habitats. Reproductive rates appeared unchanged with decline. Although demographic cause decline was clearly elevated stranded carcasses were rare or absent. net rate energy gain by length prey biomass density, all increased after varied inversely density beyond area within showed no increases anomalies, disease, contaminant exposure, abnormal gene transcription as compared animals outside These collective findings are inconsistent nutritional limitation, contaminants, consistent predation (or possibly some other density-independent factor) reason for Our approach analyses provide a broad conceptual template thinking assessing causes wildlife declines.