Meeting Abstract

68.6  Saturday, Jan. 5  Energy expenditure is independent of dive function in a deep diving vertebrate, the northern elephant seal MEIR, J.U.; University of British Columbia

Although energetics are fundamental to animal ecology, traditional methods of assessing metabolic rate are not both direct and instantaneous. Recently, continuous blood oxygen (O2) measurements were used to document energy expenditure in diving elephant seals (Mirounga angustirostris), demonstrating that an exceptional hypoxemic tolerance and exquisite management of blood O2 stores underlie their extraordinary diving capability. Despite numerous behavioral and ecological diving studies and a growing body of physiological data, we lack a clear understanding of how diving behavior affects energy expenditure in air-breathing vertebrates. To begin to unravel these relationships, we analyzed dive profiles and classified O2 utilization according to dive type (overall function of dive: transit, foraging, food processing/rest), linking fine scale behavior with in vivo O2 measurements for the first time in a free-diving animal at sea. In routine dives of elephant seals, the blood O2 store was significantly depleted to a consistent level for dives of the same duration irrespective of dive function, indicating that all dive types have equal costs. Thus, although elephant seals appear to devote one major task to a given dive, thereby separating dive functions into distinct dive types, each of these bears the same sizeable expense. This strategy may optimize O2 store utilization and recovery, consequently maximizing time underwater and allowing these animals to take full advantage of their underwater resources. Additional studies integrating dive behavior and physiology will provide a more complete understanding of the ecology and conservation needs of these animals. This may be especially important to species like the elephant seal that operate regularly at considerable cost, particularly in determining their ability to cope with unpredictable environmental perturbations.