Population structure and social organization of southern elephant seals, Mirounga leonina (L.)

The population structure and social organization of the Southern Elephant Seal, Mirounga leonina, were studied at South Georgia principally by extensive field census work and determination of age and reproductive history from sections of teeth taken from samples of bulls and cows. The adult males of the South Georgia population were exploited from 1910 to 1964, mainly at the maximum sustainable yield for this population. The present data are compared with similar information obtained from studies at South Georgia in 1951 during the exploitation phase and at Macquarie Island in the 1950's where sealing ended in 1919 and the population had stabilized. Changes have been noted in the time of bull haul out, number of bulls ashore, cow: bull ratio, harem size and the age of harem bulls. These changes can all be attributed to the ending of exploitation. In contrast, the structure of the cow herd has not changed appreciably in the same period. In addition, differences in growth, body size and population structure still persist between the South Georgia and Macquarie Island populations and it is likely that most of them may reflect differences in food availability at the two locations