title: No evidence of metabolic depression in Western Alaskan juvenile Steller sea lions (Eumetopias jubatus).
abstract: Steller sea lion (Eumetopias jubatus) populations have undergone precipitous declines through their western Alaskan range over the last four decades with the leading hypothesis to explain this decline centering around changing prey quality, quantity, or availability for this species (i.e., nutritional stress hypothesis). Under chronic conditions of reduced food intake sea lions would conserve energy by limiting energy expenditures through lowering of metabolic rate known as metabolic depression. To examine the potential for nutritional stress, resting metabolic rate (RMR) and body composition were measured in free-ranging juvenile Steller sea lions (N = 91) at three distinct geographical locations (Southeast Alaska, Prince William Sound, Central Aleutian Islands) using open-flow respirometry and deuterium isotope dilution, respectively. Average sea lion RMR ranged from 6.7 to 36.2 MJ d(-1) and was influenced by body mass, total body lipid, and to a lesser extent, ambient air temperature and age. Sea lion pups captured in the Aleutian Islands (region of decline) had significantly greater body mass and total body lipid stores when compared to pups from Prince William Sound (region of decline) and Southeast Alaska (stable region). Along with evidence of robust body condition in Aleutian Island pups, no definitive differences were detected in RMR between sea lions sampled between eastern and western populations that could not be accounted for by higher percent total body lipid content, suggesting that that at the time of this study, Steller sea lions were not experiencing metabolic depression in the locations studied.
authors.affiliation: Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Hoopes
authors.affiliation: Alaska Department of Fish and Game, Division of Wildlife Conservation, Anchorage, Alaska, United States of America.
authors.forename: Lorrie D
authors.initials: LD
authors.lastname: Rea
authors.affiliation: Alaska Department of Fish and Game, Division of Wildlife Conservation, Anchorage, Alaska, United States of America.
authors.forename: Aaron
authors.initials: A
authors.lastname: Christ
authors.affiliation: Department of Biology, University of Central Florida, Orlando, Florida, United States of America.
authors.forename: Graham A J
authors.initials: GA
authors.lastname: Worthy
mesh_terms: D000367:Age Factors; D000413:Alaska; D000818:Animals; D001481:Basal Metabolism; D001823:Body Composition / Q000502:physiology*; D041961:Deuterium Exchange Measurement; D005260:Female; D050356:Lipid Metabolism; D008297:Male; D011157:Population Dynamics; D046070:Sea Lions / Q000378:metabolism*