Feeding cycles in captive harbour seals(Phoca vitulina):Weight gain in spite of reduced food intake and increased thermal demands

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Abstract
Food intake, body mass, activity levels and social interactions of one juvenile, one yearling, and three adult (one female, two males) captive harbour seals (Phoca vitulina) were monitored over a twelve month period beginning soon after the birth of a single stillborn pup. Food intake was at its lowest during the breeding season in July, and then peaked at the end of moulting in late August, staying high until the end of September. Thereafter, food consumption fell progressively for the remaining nine months of the study, however, the seals’ body mass increased steadily. By the spring, the two adult males had augmented their mass by 32% and 29% respectively. Weight gain was negatively correlated with water temperature. Locomotor activity varied directly with food intake. Similar to the previous year when pupping was successful, two cycles of feeding intensity were found. However, unlike in the previous year, a third cycle was not statistically differentiated. Daily records of social interactions suggested that the more limited observations of activity scores in the earlier report (Renouf et al., 1988) may have been a reflection of social behaviour during the breeding/moulting period.