MOLT ENERGETICS OF THE NORTHERN ELEPHANT SEAL (MIROUNGA-ANGUSTIROSTRIS)

Northern elephant seals, Mirounga angustirostris, undergo an annual moult during which they shed all of their pelage and underlying epidermis. Moulting takes place on land and lasts a mean of 32.0 +/- 6.6 days. During this time the mean mass loss of adult females was 24.7 +/- 6.1%. Mean body composition at arrival (25.6 +/- 4.8% fat) did not differ significantly from that at departure (24.9 +/- 3.2% fat). Fat catabolism accounted for 93.6% of derived energy and 41% of mass lost. Approximately 3.5% of total mass loss was associated with the shedding of the pelage and epidermis. Moulting female northern elephant seals express an average daily metabolic rate of 2.0 +/- 0.6 times that predicted for adult terrestrial mammals. This energy demand was met by losing 3.0 kg d-1 of total body mass. These energy expenditures suggest that, similar to data for harbour seals, the moult period is a time of relatively low energy expenditure.