Neonatal Growth of Northwest Atlantic Harp Seals, Pagophilus groenlandicus

Abstract

Morphometric data were obtained from 219 neonatal harp seals in the Northwest Atlantic in March and April, 1976 to 1979. At birth, pups weighed 10.8 ± 0.65 kg and grew at a rate of 2.5 kg/day during the nursing period, which lasted about 9 days. Much of this weight gain (1.9 kg/day) was associated with deposition of the subcutaneous layer of insulating fat, with the remainder accounted for by growth of the lean body mass. During the post-weaning period, total body weight declined considerably from the weaning weight. Energy was lost primarily from the core, which decreased in weight by 35%; the weight of the blubber layer with pelt attached declined by only 10%. Maintenance of the blubber layer may be necessary to facilitate homeothermy by reducing heat loss as the young seal begins to forage in the aquatic environment. In view of the complex series of events experienced by newly-weaned harp seals, the common assumption that natural mortality is constant over all age classes warrants further investigation.