EARLY GROWTH AND MILK-COMPOSITION IN SOUTHERN ELEPHANT SEALS (MIROUNGA-LEONINA)

Growth rates and changes in body composition of pups were monitored du ring the 3-week lactation period of southern elephant seals at Macquar ie Island. Despite a slight decrease in weight in the first days post- partum, pups attained a mass of 114+/-16.6 kg (mean+/-s.d.) at weaning , representing an average growth rate of 3.53+/-0.80 kg day-1 over the entire lactation period. The proportion of body mass represented by f at was less than 3% at birth, increasing to 40.8+/-12.7% at weaning. L ean tissue mass altered little for most of the lactation period, but d id show an increase in the last four days. The fat content of the milk reflected these changes, starting at 16.1+/-6.98% on Day 1 of lactati on and increasing to 39.5+/-15.2% about the time of weaning. Fat conte nt of the milk was, however, highly variable and at weaning ranged fro m 7% to 55%. Although the growth rate of the pup was correlated with m ass lost by its mother during lactation, there was no relationship bet ween maternal mass and weaning weight of pups. It is suggested that gr owth rates may be related to maternal condition and not simply mass, a nd, further, that differences in growth rates between populations of s outhern elephant seals are related to maternal energy reserves.