Postweaning behaviour in pups of the southern elephant seal (Mirounga leonina) on South Georgia

After weaning, southern elephant seal pups (Mirounga leonina) fast for 3 – 8 weeks, for largely unknown reasons. During the postweaning fast we observed daytime behaviour and movements of pups on South Georgia in relation to mass, sex, and tooth eruption. There was variation in behaviour, with the lowest levels of activity from about 09:00 to 15:00. When ashore, weaned pups spent 97% of the time resting. There was no difference in activity between the sexes, except that only male pups were observed fighting. There was a significant difference in tooth eruption between the sexes. In female pups, 87.9% had teeth at weaning, while only 28.7% of male pups had. There was no correlation between mass at weaning and activity in either sex. Weaned pups tended to gather in groups (median group size 3, range 2 – 67). Several factors may affect the behaviour of pups during the postweaning fast: the resting behaviour required to save energy favours spending time ashore during the day (which also enhances vitamin D synthesis), and foraging is more effectively practiced at night because their prey is more active at night.

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