Ontogeny of diving behaviour in the Australian sea lion: trials of adolescence in a late bloomer

摘要: Summary 1 Foraging 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 examine how pups juveniles forage successfully. 2 Time/depth recorders were deployed on pups, adult at Seal Bay Conservation Park, Kangaroo Island, South Australia. Ten different mother/pup pairs equipped three stages development (6, 15 23 months) record 51 (nine instruments failed) animals. 3 Dive depth duration increased with age. However, was slow. At 6 months, demonstrated minimal activity mean for 23-month-old only 44 ± 4 m, or 62% depth. 4 Although did not reach depths durations, records young lions indicate times (2·0 ± 0·2 min) similar those (2·1 ± 0·2 min). This accomplished by spending higher proportions each total time near than adults. Immature also spent a percentage diving. 5 Juveniles may work harder because they are weaned before reaching full capability. For foragers, reduced ability limits available foraging habitat. Furthermore, as appear operate close physiological maximum, would difficult increasing effort in response reductions prey. Although prey less influenced seasonal fluctuations oceanographic perturbations epipelagic prey, demersal fishery trawls impact juvenile survival disrupting habitat removing size classes These issues be important factor why population is currently risk.