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AGE‐ AND SEX‐SPECIFIC MORTALITY AND POPULATION STRUCTURE IN SEA OTTERS
Author(s) -
Bodkin James L.,
Burdin Alexander M.,
Ryazanov Dmitry A.
Publication year - 2000
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.2000.tb00913.x
Subject(s) - otter , juvenile , predation , population , biology , demography , sex ratio , geography , ecology , population density , zoology , fishery , sociology
A bstract We used 742 beach‐cast carcasses to characterize age‐ and sex‐specific sea otter mortality during the winter of 1990‐1991 at Bering Island, Russia. We also examined 363 carcasses recovered after the 1989 grounding of the T/V Exxon Valdez , to characterize age and sex composition in the living western Prince William Sound (WPWS) sea otter population. At Bering Island, mortality was male‐biased (81%), and 75% were adults. The WPWS population was female‐biased (59%) and most animals were subadult (79% of the males and 45% of the females). In the decade prior to 1990‐1991 we found increasing sea otter densities (particularly among males), declining prey resources, and declining weights in adult male sea otters at Bering Island. Our findings suggest the increased mortality at Bering Island in 1990‐1991 was a density‐dependent population response. We propose male‐maintained breeding territories and exclusion of juvenile females by adult females, providing a mechanism for maintaining densities in female areas below densities in male areas and for potentially moderating the effects of prey reductions on the female population. Increased adult male mortality at Bering Island in 1990‐1991 likely modified the sex and age class structure there toward that observed in Prince William Sound.