Seasonal dispersion and habitat use of foraging northern elephant seals

• Main Authors: Stewart, Brent S, Delong, Robert L
• Format: Book Part
• Language: unknown
• Published: Oxford University PressOxford 1993
• Subjects: Elephant Seal; Elephant Seals; Subarctic
• Online Access: http://dx.doi.org/10.1093/oso/9780198540694.003.0010; https://academic.oup.com/book/chapter-pdf/52430136/isbn-9780198540694-book-part-10.pdf

Abstract Elephant seals are at sea and dive continously for 8-10 months each year. They range widely in the North Pacific; their dispersion and migratory patterns correspond with three major North Pacific oceanographic features where enhanced biological productivity supports deep-water assemblages of elephant seals’ primary cephalopod prey. Throughout the year adult males are dispersed farther north than females. Both sexes forage primarily on squid that reduce their specific gravity to maintain neutral buoyancy either by storing fat in their bodies or by actively replacing heavy metal ions in their body fluids with lighter ammonium ions. Squid with these adaptations are slower swimmers, and therefore probably more susceptible to predation by elephant seals, but are of poorer nutritional quality than are negatively buoyant squid species. Adult elephant seal males may gain access to higher-quality prey than females by travelling farther north to capitalize on larger fat-rich gonatid squid, the dominant cephalopod fauna in the Subarctic water mass. It is not clear why females do not forage in those northern areas. But reduced intraspecific competition for food resources because of such sexual segregation of foraging adults has important implications for demographic studies of the rapidly growing northern elephant seal population.