Meeting Abstract
Pinnipeds (seals, sea lions, walrus) are a unique group of mammals that feed in the ocean but return to land for breeding and molting. Harp seals (Pagophilus groenlandicus) live in the frigid Arctic and rely on thick insulation to maintain thermal homeostasis. Adult harp seals primarily use blubber for insulation, but newborn harp seals rely on a fur coat as their blubber layer develops. After harp seal pups are weaned at 12 days old, they must learn to swim and dive in Arctic waters on their own. This study examined ontogenetic changes in the thermal properties of harp seal fur in water. Thermal conductivity, thermal resistance, and fur thickness were compared in air and water for pelts of harp seal neonates (1d old, N=7), thin whitecoats (4d old, N=3), fat whitecoats (9d old, N=4), molting pups (2w old, N=4), molted pups (3w old, N=5), and adults (N=4). Fat whitecoat pelts had significantly higher thermal conductivity in air (P<0.001), whereas thin whitecoat pelts had significantly higher thermal conductivity in water (P=0.014). Thermal resistance of the pelt in air decreased with age (P<0.001), with a significant reduction just prior to the molt. Thermal resistance of the pelt was significantly reduced in water compared to air, across age classes (P<0.001). In older pups and adults this decrease in thermal function was balanced by a thick blubber layer. The lanugo hairs of pre-molt pups increased in height rather than flattening underwater, a phenomenon that has never been reported. This unusual occurrence may create a buffer in water, similar to a wetsuit. Overall, fur represents an important component of thermoregulation for harp seal pups on land, whereas the development of a thick blubber layer is key to their transition to a predominantly aquatic lifestyle.
