Metabolism and temperature regulation in young harbor seals Phoca vitulina richardi

Metabolism and the ability to regulate core and peripheral temperatures under a variety of ambient conditions were studied in five unrestrained pups (less than 5 wk old) and four 3- to 5-mo-old harbor seals. Pups born with nonlanugo (adultlike) hair and little fat were able to swim in 5 degrees C water for several hours without becoming hypothermic. They were also found to tolerate 5 degrees C air temperature with the fur wet and exposed to a 35-knot wind. Basal metabolism in pups averaged 0.8 ml O2 g-1 h-1, which is 2.6 times the predicted value for an adult mammal of the same weight. Lower critical temperature in air was about 3 degrees C. Oxygen uptake in 3- to 5-mo-old seals under basal conditions was 0.5 ml g-1 h-1. Minimal thermal conductance values were .02 and .015 ml O2 g-1 h-1 degrees C-1 in pumps and 3- to 5-month-old seals, respectively. Appendages, and to a lesser extent the skin on the torso, cooled appreciably at lower air temperatures, and the flippers were kept just above freezing in subzero air. Tissue insulation provided by low peripheral temperatures and a high resting metabolic rate enable newborn and developing harbor seals to tolerate the low temperatures encountered in their natural environment.