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Marine Ecology Progress Series

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MEPS 363:299-309 (2008)  -  DOI:

Multiple foraging strategies in a marine apex predator, the Galapagos sea lion Zalophus wollebaeki

Stella Villegas-Amtmann1,*, Daniel P. Costa1, Yann Tremblay1, Sandie Salazar2,3, David Aurioles-Gamboa2

1Department of Ecology and Evolutionary Biology, Long Marine Laboratory, 100 Shaffer Road, University of California Santa Cruz, Santa Cruz, California 95060, USA
2Centro Interdisciplinario de Ciencias Marinas, IPN, La Paz, Baja California Sur, Mexico
3Charles Darwin Foundation, Puerto Ayora, Galapagos, Ecuador

ABSTRACT: Three fundamental foraging patterns in air-breathing marine vertebrates have been described: epipelagic, mesopelagic and benthic. Many sea lion species with access to extensive continental shelves have been described as benthic foragers. Coincidently these species are considered threatened. The Galapagos sea lion Zalophus wollebaeki, a top predator in the Galapagos Islands, is also considered threatened in this ecosystem. Sea lions at the central part of the archipelago have access to a vast continental shelf. For this reason we hypothesized that sea lions within this region would dive benthically. In addition, effective protection and conservation of this species requires knowledge of their foraging patterns and habitat utilization. We investigated the diving behaviour and habitat utilization of female Z. wollebaeki of a centrally located colony situated inside the highest density area of the population using time-depth recorders and satellite telemetry. Three distinct foraging patterns were found and described (shallow, deep and bottom divers), and individuals utilizing each pattern foraged in different locations. Epipelagic, mesopelagic and benthic dives were exhibited in the sea lions’ diving behaviour, but these dive types were not exclusively associated with a foraging pattern. Between foraging trips females hauled out more frequently on other islands than they did on their breeding colony. The finding of 3 distinct foraging patterns that differ spatially has direct implications for management, particularly with regard to fisheries interactions. Marine protected areas can be implemented in the regions described as Z. wollebaeki foraging areas. Z. wollebaeki’s wide foraging range coupled with their use of multiple haul-out sites should be considered in future studies when determining foraging trip lengths and habitat utilization since presence/absence from the colony does not reflect foraging trip length.

KEY WORDS: Diving behaviour · Foraging behaviour · Galapagos Islands · Habitat utilization · Individual specialization · Galapagos sea lion · Zalophus wollebaeki

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Cite this article as: Villegas-Amtmann S, Costa DP, Tremblay Y, Salazar S, Aurioles-Gamboa D (2008) Multiple foraging strategies in a marine apex predator, the Galapagos sea lion Zalophus wollebaeki. Mar Ecol Prog Ser 363:299-309.

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