Foraging success and efficiency in lactating female southern sea lions

Myriam Lebon

Foraging efficiency is influenced by quantity and quality of prey captures, habitat use and strategies. Success and efficiency in foraging trips is linked to survival, fitness and reproductive success. Yet, little is known about foraging strategies and energy outcomes. The foraging behaviour and energy expenditure of 17 lactating female southern sea lions (Otaria flavescens) were investigated to determine the consequences of environmental changes and human impact on the population. Using tracking devices combined with behaviour data loggers, individual foraging trips characteristics were determined and compared. Females foraged both inshore in shallow coastal waters (17.4 ± 0.2m) and offshore over the Patagonian shelf and shelf edge. Females foraging offshore used either a benthic (79.8 ± 1.0m) or mixed (benthic and pelagic) operating mode (49.8 ± 0.8m). Potential Prey Captures (PPC) could be identified and energy expended estimated via Vectoral Dynamic Body Acceleration (VeDBA). The number of PPC (mean = 424.8 ± 69.1), PPC rate (mean = 0.7 ± 0.1), and VeDBA were examined for of all three foraging groups. Foraging group influenced the number of PPC, but not energy expenditure. These findings participate in expending knowledge of SSL and allow a better understanding of their habitat use and foraging ecology.