SEASONAL-CHANGES IN BLUBBER DISTRIBUTION IN ATLANTIC HARBOR SEALS - INDICATIONS OF THERMODYNAMIC CONSIDERATIONS

Among its functions, the hypodermal blubber layer of pinnipeds serves as both an energy reserve and insulation. This study examined seasonal changes in blubber distribution and body morphology in a group of cap tive harbor seals to test whether these changes were designed to maxim ize insulative effectiveness. Seasonal changes were found in girth, bl ubber volume, mean blubber depth, and the ratio of blubber depth to bo dy radius (dir ratio). These changes were more evident in older seals. The dir ratio demonstrated a smaller relative annual change than mean blubber depth. The dir ratio also exhibited less variation along the length of the seal than blubber depth at any given time. Similar to re ports for ringed seals, and contrary to those for southern elephant se als, the harbor seals preferentially lost blubber from overinsulated a reas of the body. These results suggest that core tissue and blubber m ass are lost in a manner that maximizes insulative effectiveness.