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Determinants of individual foraging specialization in large marine vertebrates, the Antarctic and subantarctic fur seals.

journal contribution
posted on 2015-07-01, 00:00 authored by Laetitia Kernaleguen, John ArnouldJohn Arnould, C Guinet, Y Cherel
The degree of individual specialization in resource use differs widely among wild populations where individuals range from fully generalized to highly specialized. This interindividual variation has profound implications in many ecological and evolutionary processes. A recent review proposed four main ecological causes of individual specialization: interspecific and intraspecific competition, ecological opportunity and predation. Using the isotopic signature of subsampled whiskers, we investigated to what degree three of these factors (interspecific and intraspecific competition and ecological opportunity) affect the population niche width and the level of individual foraging specialization in two fur seal species, the Antarctic and subantarctic fur seals (Arctocephalus gazella and Arctocephalus tropicalis), over several years. Population niche width was greater when the two seal species bred in allopatry (low interspecific competition) than in sympatry or when seals bred in high-density stabilized colonies (high intraspecific competition). In agreement with the niche variation hypothesis (NVH), higher population niche width was associated with higher interindividual niche variation. However, in contrast to the NVH, all Antarctic females increased their niche width during the interbreeding period when they had potential access to a wider diversity of foraging grounds and associated prey (high ecological opportunities), suggesting they all dispersed to a similar productive area. The degree of individual specialization varied among populations and within the annual cycle. Highest levels of interindividual variation were found in a context of lower interspecific or higher intraspecific competition. Contrasted results were found concerning the effect of ecological opportunity. Depending on seal species, females exhibited either a greater or lower degree of individual specialization during the interbreeding period, reflecting species-specific biological constraints during that period. These results suggest a significant impact of ecological interactions on the population niche width and degree of individual specialization. Such variation at the individual level may be an important factor in the species plasticity with significant consequences on how it may respond to environmental variability.

History

Journal

Journal of animal ecology

Volume

84

Issue

4

Pagination

1081 - 1091

Publisher

Wiley-Blackwell Publishing

Location

Chichester, Eng.

ISSN

0021-8790

eISSN

1365-2656

Language

eng

Publication classification

C Journal article; C1 Refereed article in a scholarly journal

Copyright notice

2015, Wiley-Blackwell Publishing