Same size same niche? Foraging niche separation between sympatric juvenile Galapagos sea lions and adult Galapagos fur seals
Authors/Editors
Research Areas
Publication Details
Output type: Journal article
Author list: Jeglinski JWE, Goetz KT, Werner C, Costa DP, Trillmich F
Publisher: Wiley
Publication year: 2013
Journal: Journal of Animal Ecology (0021-8790)
Volume number: 82
Issue number: 3
Start page: 694
End page: 706
Number of pages: 13
ISSN: 0021-8790
eISSN: 1365-2656
Languages: English-Great Britain (EN-GB)
Unpaywall Data
Open access status: bronze
Full text URL: https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/1365-2656.12019
Abstract
In vertebrates, patterns of resource utilization change throughout development according to age- and or size-specific abilities and requirements. Thus, interspecific competition affects different age classes differently. Adults of sympatric species often show distinct foraging niche segregation, but juvenile resource use might overlap with adult competitors of similar body size. Resultant negative effects on juveniles can have important consequences for population dynamics, yet such interactions have received little attention in studies of mammalian communities. Using GPS tracking devices, time-depth recorders and stable isotope data, we compared diving depth, activity time, trophic position and foraging habitat characteristics to investigate foraging niche overlap between similar-sized sympatric juvenile Galapagos sea lions (Zalophus wollebaeki) and adult Galapagos fur seals (Arctocephalus galapagoensis) and compared each group with much larger-bodied adult Galapagos sea lions. We found little indication for direct competition but a complex pattern of foraging niche segregation: juvenile sea lions and adult fur seals dived to shallow depths at night, but foraged in different habitats with limited spatial overlap. Conversely, juvenile and adult sea lions employed different foraging patterns, but their foraging areas overlapped almost completely. Consistency of foraging habitat characteristics between juvenile and adult sea lions suggests that avoidance of competition may be important in shaping foraging habitat utilization. Resultant specialization on a limited habitat could contribute to low sea lion numbers that contrast with high fur seal abundance. Our data suggest that exploitation by multiple predators within spatially restricted foraging ranges of juveniles might negatively impact juvenile foraging success and ultimately influence population dynamics.
Keywords
Arctocephalus galapagoensis, biologging, foraging competition, habitat segregation, ontogeny, stable isotopes, Zalophus wollebaeki
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