The foraging ecology of South American sea lions (Otaria flavescens) on the Patagonian Shelf
The aim of this study was to elucidate the foraging ecology of South American sea lions (Otaria flavescens) on the Patagonian shelf. Data from satellite tags revealed that male sea lions use a much larger part of the shelf than females and often reach areas close to the shelf break, which may be related to the highly productive shelf break front. The data also showed a high site fidelity, both towards feeding grounds and haul-out sites. Calculations of food consumption revealed that the impact that males have on their prey resources depends on the time that the animals spend at sea, and thus the distance to suitable foraging grounds. A new non-electronic release-mechanism was developed for the recovery of dead reckoners that were used to study the diving behaviour of sea lions. The diving data supported the expectations that males, because of their larger size, had a greater diving capacity than females, which lead to a greater dive efficiency at depths greater than 45m. The use of an Area-Interest-Index to determine space usage revealed that sea lion foraging trips can be divided into distinctive travel and foraging phases. Differences in this index were also visible on the scale of individual dives.