Preliminary comparison of calls of the hybridizing fur seals Arctocephalus tropicalis and A. gazella

Abstract

The Antarctic fur seal (Arctocephalus gazella) and the Subantarctic fur seal (A. tropicalis) hybridize on a relatively small scale at Marion Island. To date the description of calls published for A. tropicalis and A. gazella are fragmented and not easily compared.We compare the vocal signalling of males and females of the two species of fur seals to aid understanding of the factors involved in hybridization. Five call types were compared: barking, guttural challenges and territorial calls emitted by adult males; the pup attraction call used by adult females and the response: female attraction call emitted by pups. The calls emitted by males of the two species have certain similarities but are separated by multivariate analyses. By contrast, the calls of females and pups of the two species are more similar and do not cluster separately. Since many of the differences in male calls are audible to the human ear, female seals can presumably also hear these differences and we suggest that interbreeding of the two fur seal taxa is not caused by similarity in male vocal communication. Following this preliminary study, further behavioural studies are required for a fuller understanding of hybridization in these animals.

Key words: fur seals, sound communication, mate recognition, systematics, Marion Island.