| Summary: | To account for the repetitive, long duration dives of the northern elephant seal, Mirounga angustirostris , it has been hypothesized that this species must either become "hypometabolic", or, contrary to current concepts of aerobic dive limits, must resort to glycolysis and lactate accumulation during dives. As recent studies have revealed reductions in regional temperature during diving, it is possible that hypothermia may serve as a mechanism of reducing oxygen consumption and extending aerobic dive time. To document core body temperature during diving in this species, a thermistor was inserted into extradural vein, hepatic sinus, or aortic sites and a backpack recorder attached to translocated, juvenile elephant seals. Venous temperature during routine dives remained near 37°C. Arterial temperature profiles, however, often revealed increases during diving (similar to that of exercising mammals), even to greater than 40°C, with subsequent decreases during each surface interval. Decreases in venous and arterial temperature to as low as 31‐34°C did occur in long (>30 min) dives, though these drops were transient and re‐warming occurred prior to the end of dive. These data suggest that hypothermia‐induced hypometabolism is an unlikely contributor to metabolic suppression while diving. Funding: NSF grant IOS‐0641801 & SIO Halliday Student Field Research Award
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