Ontogeny of diving behaviour in the Australian sea lion: trials of adolescence in a late bloomer
Article first published online: 31 MAR 2006
Journal of Animal Ecology
Volume 75, Issue 2, pages 358–367, March 2006
How to Cite
FOWLER, S. L., COSTA, D. P., ARNOULD, J. P. Y., GALES, N. J. and KUHN, C. E. (2006), Ontogeny of diving behaviour in the Australian sea lion: trials of adolescence in a late bloomer. Journal of Animal Ecology, 75: 358–367. doi: 10.1111/j.1365-2656.2006.01055.x
- Issue published online: 31 MAR 2006
- Article first published online: 31 MAR 2006
- Received 29 June 2005; revised version accepted 24 October 2005
- benthic diving;
- foraging ecology;
- Neophoca cinerea;
- postnatal development;
- 1Foraging behaviours of the Australian sea lion (Neophoca cinerea) reflect an animal working hard to exploit benthic habitats. Lactating females demonstrate almost continuous diving, maximize bottom time, exhibit elevated field metabolism and frequently exceed their calculated aerobic dive limit. Given that larger animals have disproportionately greater diving capabilities, we wanted to examine how pups and juveniles forage successfully.
- 2Time/depth recorders were deployed on pups, juveniles and adult females at Seal Bay Conservation Park, Kangaroo Island, South Australia. Ten different mother/pup pairs were equipped at three stages of development (6, 15 and 23 months) to record the diving behaviours of 51 (nine instruments failed) animals.
- 3Dive depth and duration increased with age. However, development was slow. At 6 months, pups demonstrated minimal diving activity and the mean depth for 23-month-old juveniles was only 44 ± 4 m, or 62% of adult mean depth.
- 4Although pups and juveniles did not reach adult depths or durations, dive records for young sea lions indicate benthic diving with mean bottom times (2·0 ± 0·2 min) similar to those of females (2·1 ± 0·2 min). This was accomplished by spending higher proportions of each dive and total time at sea on or near the bottom than adults. Immature sea lions also spent a higher percentage of time at sea diving.
- 5Juveniles may have to work harder because they are weaned before reaching full diving capability. For benthic foragers, reduced diving ability limits available foraging habitat. Furthermore, as juveniles appear to operate close to their physiological maximum, they would have a difficult time increasing foraging effort in response to reductions in prey. Although benthic prey are less influenced by seasonal fluctuations and oceanographic perturbations than epipelagic prey, demersal fishery trawls may impact juvenile survival by disrupting habitat and removing larger size classes of prey. These issues may be an important factor as to why the Australian sea lion population is currently at risk.