The diving and ranging behaviour of southern elephant seal, Mirounga leonina, bulls

Abstract

Geolocation-Time-depth Recorders (GLTDRs) were used to record the diving and ranging behaviour of eleven southern elephant seal, Mirounga leonina, adult males from sub-Antarctic Marion ( n = 7) and Macquarie ( n = 4) Islands during their pelagic annual cycle. A total of 39 897 dives during 894 days were recorded and were categorised into twelve dive types which were hypothesized to serve in travelling, searching for prey, exploration, resting, benthic foraging, pelagic foraging and combinations of two or more functions, and seals dived virtually continuously (86%-92% of the time underwater) most often to depths ranging from 390 m to 920 m and dive durations from 18.6 min to 36.6 min (maximum duration= 80 min) spending only 2.4 min to 3.6 min on the surface between dives. Although the maximum measured dive depths for two males from Marion Island (1 446 m and I 452 m) are the deepest dives measured yet for male southern elephant seals, these seals often exceeded the depth limit of the GLTDRs. The Macquarie males travelled to Antarctica mostly foraging benthically over the Antarctic continental shelf whilst the males from Marion Island stayed relatively close to the island, diving deeper and longer pursuing pelagic prey species. The results in this study suggest that different physical environmental conditions resulted in the different diving behaviours displayed by M leonina males. 11