Maternal aggression in the South American fur seal in Peru

Arctocephalus australis was studied at Punta San Juan. Female fur seals' responses to conspecifics and to predatory southern sea lions Otaria byronia were examined pre- and post-partum. Mothers rarely defended their offspring from raiding sea lions, possibly due to the high risks involved in attacking a large and potentially very dangeorus predator. The costs of defending the pup from sea lions appeared to outweigh the potential benefit of increased survival of the pup, due to the already high pup mortality at the site. Females with newborn pups were more aggressive towards other females than were females without pups, particularly during the perinatal attendance period. They threatened a higher proportion of approaching females and won more aggressive encounters postpartum. However, mothers of surviving pups did not appear to be any more aggressive, their pups did not receive any fewer threats from unrelated females, nor did they reside in areas of less aggression, than mothers whose pups died. Aggression towards male conspecifics appeared to serve a further purpose, as females threatened approaching adult and subadult males regardless of whether the females had a pup. -from Author