The Foraging Success of Southern Elephant Seals ( Mirounga leonina ) Dispersing to the West and East of the Kerguelen Archipelago

Abstract

Foraging behavior and success are a function of prey abundance and distribution in marine environments. Oceanographic processes shape prey spatial structuring, leading to some areas of high heterogeneity and others of high homogeneity, causing marine predators to exhibit different at‐sea behaviors. Our study investigated foraging success and effort of adult female southern elephant seals dispersing west or east of the Kerguelen Plateau. We quantified drift dive data and dive metric data for 153 seals, focusing on timing and spatial patterns in seal buoyancy change and its relationship with seal dive behavior. We assessed whether differences were linked to differing responses to forage quality. Overall, buoyancy changes indicated elephant seals had similar foraging success in both homogeneous (west) and heterogeneous (east) environments around the Kerguelen Plateau. Seals to the east dived deeper, with shorter hunting times and higher descent rates, probably related to higher mesoscale activity, while those to the west had lower descent rates and focused on shallower prey. Both groups responded to changes in forage quality by increasing ascent/descent rate in high‐quality areas. These results suggest that these seals behave as predicted by the marginal value theorem and in so doing adapt foraging behavior to efficiently exploit profitable prey patches.

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