Repertoire and Geographic Variation in Underwater Vocalisations of Weddell Seals (Leptonychotes weddellii, Pinnipedia : Phocidae) at the Vestfold Hills, Antarctica

Abstract

The underwater vocalisations of Weddell seals (Leptonychotes weddellii) near Davis, Antarctica, were many and varied. A total of 11029 vocalisations recorded throughout and immediately after the breeding season were analysed. Vocalisations were classified by cluster analysis techniques, based on differences in frequency, duration, call shape, waveform and number of elements. Thirteen broad call categories (many with subdivisions) were identified. Twelve call types (belonging to nine categories) made up 91· 9% of the vocalisations and were present at all seven study sites within the Vestfold Hills, and a single site at the Larsemann Hills approximately 150 km away. A further eight call types (five categories) made up another 6·7% of the vocalisations. These were not detected at every recording site. An additional 29 call types (11 categories) were infrequent and probably reflect the diversity of individual seals. This study strengthens the case for macrogeographic variation in underwater Weddell seal vocalisations around Antarctica. Microgeographic differences, between sites within 150 km, were weak and not consistent between sites or years. Some adult females move to different breeding sites within the Vestfold Hills area between years. This would probably preclude the establishment of site-specific (microgeographic) repertoire differences.