Fine-scale hunting strategies in Australian fur seals (Arctocephalus pusillus doriferus)

Perla Salzeri

Individual survival and fitness are linked to the success of foraging activities. The optimisation of foraging behaviours is based on the evaluation of the costs and benefits of engaging a certain strategy to balance the energy expenditure of living. The present study investigated the foraging strategies of Australian fur seals (Arctocephalus pusillus doriferus) at the intra- and inter-dive level using 3D models. A combined video/depth/IMU (inertial measurement unit) data logger was placed to their back. VeDBA and average speed were calculated for all dive phases, together with average descent and ascent pitch, and number of directional turns along the bottom. Individuals were found to maximise their proportion spent at the foraging zone by increasing pitches and decreasing the energetic costs during descent and ascent phases. The energy spent at the foraging zone was greatly influenced by the presence of directional turns, however, it was compensated with the increase in prey rate. In addition, individuals were found to maintain the same heading when prey captures occurred, hence, conventionally described Area Restricted Search was found not to be occurring. As a result of sea temperature rise, prey distribution will change, hence it is important to further investigate foraging strategies of this species.