Weaning mass and the future survival of juvenile southern elephant seals, Mirounga leonina, at Macquarie Island

Seals that survived their first year were on average 2% and 4% heavier at birth and at weaning than the 'non-survivors'. First year survival rates calculated for weaners over 135 kg weaning masses showed these weaners had higher survival rates than those less than 95 kg at weaning (71.55% and 54.15% respectively). Heavy weaners had greater fat reserves than light weaners and gained relatively more mass during lactation. Size, and therefore condition at weaning, influences first year survival.