Southern elephant seals (Mirounga leonina) are among the most proficient of mammalian divers and are a major component of the Antarctic food web. Yet little is known of their movements or interaction with their oceanic environment. Specially designed satellite-link data loggers allowed us to visualize the 3-D movements of elephant seals as they swam rapidly from South Georgia to distant (up to 2650 km) areas of Antarctic continental shelf. One seal dived continuously to the sea bed in one small area for a month, implying consumption of benthic prey. Dives here were shorter even though average swimming velocity was lower. It is suggested that the physiological requirements of feeding and digestion reduced the aerobic dive limit. Long distance travel to relocatable hydrographic or topographical features, such as shelf breaks, may allow large predators to locate prey more consistently than from mid-ocean searches.

In the summer of 1995/96, 25 southern elephant seals, Mirounga leonina, were stomach lavaged at Stranger Point, King George Island, South Shetland Islands. Cephalopod remains were present in 72% of the individuals sampled (n = 18). Seven species of squid and three of octopus were identified. The squid Psychroteuthis glacialis was the most important prey in terms of numbers (77%), biomass (80.8%) and frequency of occurrence (94.4%). Next in importance in terms of mass was the squid Alluroteuthis antarcticus (7.8%) in the diet of females and the octopodid Pareledone ?charcoti in the diet of males (13.2%). Females preyed on a wider variety of squid taxa than males (7 vs 3) but octopodids occurred only in stomach contents from males. The predominance of P. glacialis in the prey of the South Shetland Islands elephant seals can be explained by the southerly location of the foraging areas of this population compared to South Georgia, Heard and Macquarie islands, where the diet of southern elephant seals has previously been analysed. Psychroteuthis glacialis is the predominant squid in waters close to the Antarctic continent.