Journal Article

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

Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC) ; Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Guinet, Christophe, Arnould, John P. Y, Kernaleguen, Laëtitia, Cherel, Yves, School of Life and Environmental Sciences ; Deakin University [Melbourne Burwood]

2015

Overview

1. The degree of individual specialization in resource use differs widely among wild populationswhere individuals range from fully generalized to highly specialized. This interindividualvariation has profound implications in many ecological and evolutionary processes. A recentreview proposed four main ecological causes of individual specialization: interspecific andintraspecific competition, ecological opportunity and predation.2. Using the isotopic signature of subsampled whiskers, we investigated to what degree threeof these factors (interspecific and intraspecific competition and ecological opportunity) affectthe population niche width and the level of individual foraging specialization in two fur sealspecies, the Antarctic and subantarctic fur seals (Arctocephalus gazella and Arctocephalustropicalis), over several years.3. Population niche width was greater when the two seal species bred in allopatry (low interspecificcompetition) than in sympatry or when seals bred in high-density stabilized colonies (highintraspecific competition). In agreement with the niche variation hypothesis (NVH), higherpopulation niche width was associated with higher interindividual niche variation. However, incontrast to the NVH, all Antarctic females increased their niche width during the interbreedingperiod when they had potential access to a wider diversity of foraging grounds and associatedprey (high ecological opportunities), suggesting they all dispersed to a similar productive area.4. The degree of individual specialization varied among populations and within the annualcycle. Highest levels of interindividual variation were found in a context of lower interspecificor higher intraspecific competition. Contrasted results were found concerning the effect ofecological opportunity. Depending on seal species, females exhibited either a greater or lowerdegree of individual specialization during the interbreeding period, reflecting species-specificbiological constraints during that period.5. These results suggest a significant impact of ecological interactions on the population nichewidth and degree of individual specialization. Such variation at the individual level may bean important factor in the species plasticity with significant consequences on how it mayrespond to environmental variability.

• Publisher: Wiley,CCSD,John Wiley & Sons Ltd,Blackwell Publishing Ltd
• Subject: allopatry / Animal populations / Animals / Antarctic region / Antarctic Regions / Aquatic mammals / Arctocephalus / Arctocephalus gazella / Arctocephalus tropicalis / Carbon Isotopes / Competition / Competitive Behavior / diet / environmental impact / Environmental Sciences / Feeding Behavior / Female / females / foraging / Foraging behavior / foraging ecology / Fur Seals - physiology / Indian Ocean / interspecific competition / intraspecific competition / Marine ecology / Marine mammals / niche variation hypothesis / niche width / Niches / Nitrogen Isotopes / otariid / pinniped / predation / Predatory Behavior / Seals / Species Specificity / stable isotopes / Sympatry / Trophic interactions / vibrissae / Vibrissae - chemistry / whisker