Energy gain and loss during lactation and postweaning in southern elephantseal pups (Mirounga leonina) at King George Island

Deuterium-labeled water was used to measure changes in the proximate body c omposition during the lactation period and after weaning in southern elepha nt seal pups at King George Island, South Shetland Islands, Antarctica. Dur ing the lactation period (23.0 +/- 1.4 days) pups gained a mean of 4.9 +/- 0.5 kg/day (n = 7). Of the total mass gain (112 +/- 8 kg), 38% was water, 4 8% was fat, and 11% was protein. This represented an increase in total body gross energy of 2437 +/- 145 MJ. The proportion of body mass represented b y fat was less than 2% at birth, increasing to 35 +/- 2% at weaning. We fol lowed the pups during a mean period of 36 +/- 3 days after weaning. During this period, pups had a mean loss of 1.21 +/- 0.10 kg/day (n = 7) comprisin g 39% water, 48% fat, and 12% protein. The energy cost over this period was 952 +/- 168 MJ, which represented, on average, 39% of the total energy gai ned during the suckling period.