Diving behaviour of two Ross seals off east Antarctica

Abstract

The Ross seal (Ommatophoca rossii) is the least frequently sighted and least known of the Antarctic pinnipeds. Current knowledge of foraging and diving behaviour is based on observations of a single seal over <2 days. The current study provides some additional data on the diving behaviour of two Ross seals off east Antarctica over periods of 31 and 12 days during December–January 1999–2000 using satellite-linked dive recorders. Both seals remained over the continental shelf for these times, the female remaining some distance from the coast and the male moving close to the coast approximately half-way through his transmission period. Most dives by the female reached depths >150 m (maximum depth 372 m) and the modal duration was 10–11 min. The male’s dives were slightly shallower (most >100 m) and shorter (mode 6–7 min) when distant from the continental coast, and were truncated to a depth of 180 m when close to the coast, presumably by the sea floor. These dive patterns suggest that their prey species, thought to comprise mostly fish and squid, were relatively unavailable at depths <100 m.