Behavioral cues used in reunions between mother and pup South American fur seals (Arctocephalus australis)

Abstract

In South American fur seals (Arctocephalus australis) breeding in dense colonies at Punta San Juan, Peru, mothers are regularly separated from pups when they forage at sea throughout lactation and as a result of disturbances among females during on-beach nursing periods. Unattended pups risk injury or death from aggressive females and predatory sea lions, so the ability of mothers and pups to recognize and reunite is an essential component of breeding success. I investigated the relative importance of vocal, visual, olfactory, and spatial cues in the reunion process and examined how these behaviors are related to search context and success. Behavior of 10 tagged mother-pup pairs was recorded during 118 searches, 67% of which resulted in reunion. Mothers and pups appeared to recognize one another by vocal signatures over distance, and mothers used naso-nasal investigation before accepting or rejecting pups. Mothers supplemented their calling behavior with a variety of low-cost strategies such as frequenting a consistent "home spot" (76%), moving about the colony (49%), and investigating approaching pups (42%), but the best predictor of search success was pup response: after pups called and moved toward mothers, pairs were reunited 95% of the time regardless of mothers' behavior. Pups responded infrequently (18%) to the wrong female, suggesting that pups' acceptance criteria are conservative when risk of injury from unrelated females is high.