Mass and bathymetry influences on the foraging behaviour of dependent yearling New Zealand sea lions (Phocarctos hookeri)

Juvenile foraging ability is limited due to physiological and morphological constraints. Restricted foraging skills can result in reduced juvenile survival, which can lead to population decline. Given the important role mass plays in influencing foraging behaviour and survival, we deployed satellite-linked time-depth recorders (TDRs) on seven dependent yearling New Zealand sea lions (Phocarctos hookeri) over three seasons from 2008-2010 at the New Zealand subantarctic Auckland Islands to study how mass influenced at sea movements and diving behaviour. Mass was significantly negatively related to dive depth and descent rate, indicating yearling diving behaviour may be influenced by their mass. The yearlings demonstrated inter-individual variation in foraging locations and strategies. This individual variation was likely attributed to the bathymetry of different foraging areas dictating possible dive depths. Thus, when studying foraging behaviour, in addition to physiological and morphological influences, researchers must examine external factors such as the physical characteristics of the foraging habitat.