Juvenile survival and population regulation in southern elephant seals at Marion Island

Abstract

We examined annual juvenile survival in southern elephant seals (Mirounga leonina) at Marion Island for the period 1994–1999 during which time the population was stable. Using mark–recapture models, we tested for age- and sex-specific differences in survival rates over the first three years of life. We found that survival was age- but not sex-related and compared our estimates to similar estimates from a previous study on the same population while in a state of decline. This was done to determine whether changes in juvenile survival were instrumental in terminating the population decline at Marion Island. On average, the probability of survival was 59.5 %, 81.4 % and 78.1 % for the first, second and third year respectively. These estimates were remarkably similar to those previously calculated for the population while in a state of decline, and we dismiss juvenile survival as a major population regulating component in southern elephant seals at Marion Island.

Keywords: southern elephant seals, juvenile survival, mark–recapture, population regulation.