Harp seals combine anatomical and behavioral approaches to managing their body temperatures, instead of elevating their metabolic rate and energy requirements. A thick coat of blubber insulates its body and provides energy when food is scarce or during fasting. Blubber also streamlines its body for more efficient swimming. Brown fat warms blood as it returns from the body surface as well as providing energy, most importantly for just-weaned pups.
Flippers act as heat exchangers, warming or cooling the seal as needed. On ice, the seal can press its fore-flippers to its body and its hind-flippers together to reduce heat loss.