Document Detail


Stable isotopes document seasonal changes in trophic niches and winter foraging individual specialization in diving predators from the Southern Ocean.
MedLine Citation:
PMID:  17584388     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
1. Climatic variation outside the breeding season affects fluctuations in population numbers of seabirds and marine mammals. A challenge in identifying the underlying biological mechanisms is the lack of information on their foraging strategies during winter, when individuals migrate far from their breeding grounds. 2. We investigated the temporal variability in resource partitioning within the guild of five sympatric Subantarctic penguins and fur seals from Crozet Islands. The stable isotopic ratios of carbon (delta(13)C) and nitrogen (delta(15)N) for whole blood were measured for penguins and fur seals, as were the isotopic ratios for penguin nails and food. Animals were sampled at two periods, during breeding in summer and at their arrival in the colonies in spring (hereafter winter, since the temporal integration of blood amounting to several months). 3. In summer, delta(13)C and delta(15)N for blood samples defined three foraging areas and two trophic levels, respectively, characterizing four nonoverlapping trophic niches. King penguins and female Antarctic and Subantarctic fur seals are myctophid eaters foraging in distinct water masses, while both macaroni and rockhopper penguins had identical isotopic signatures indicating feeding on crustaceans near the archipelago. 4. Isotopic ratios were almost identical in summer and winter suggesting no major changes in the species niches, and hence, in the trophic structure of the guild during the nonbreeding period. A seasonal difference, however, was the larger variances in delta(13)C (and also to a lesser extent in delta(15)N) values in winter, thus verifying our hypothesis that trophic niches widen when individuals are no longer central place foragers. 5. Winter isotopic ratios of macaroni penguins and male Antarctic fur seals had large variances, indicating individual foraging specializations. The range of delta(13)C and delta(15)N values of male fur seals showed, respectively, that they dispersed over a wide latitudinal gradient (from Antarctica to north of the archipelago) and fed on different prey (crustaceans and fish). 6. By comparing summer and winter isotopic ratios and examining the summer diet, we highlight the feeding habits of marine predators that were not previously addressed. The findings have a number of implications for understanding the functioning of the pelagic ecosystem and on the demography of these species.
Authors:
Yves Cherel; Keith A Hobson; Christophe Guinet; Cecile Vanpe
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of animal ecology     Volume:  76     ISSN:  0021-8790     ISO Abbreviation:  J Anim Ecol     Publication Date:  2007 Jul 
Date Detail:
Created Date:  2007-06-22     Completed Date:  2007-09-25     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0376574     Medline TA:  J Anim Ecol     Country:  England    
Other Details:
Languages:  eng     Pagination:  826-36     Citation Subset:  IM    
Affiliation:
Centre d'Etudes Biologiques de Chizé & UPR 1934 du Centre National de la Recherche Scientifique, BP 14, F-79360 Villiers-en-Bois, France. cherel@cebc.cnrs.fr
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MeSH Terms
Descriptor/Qualifier:
Animals
Antarctic Regions
Blood Chemical Analysis
Carbon Isotopes / blood,  diagnostic use
Feeding Behavior / physiology*
Female
Food Chain*
Fur Seals*
Male
Nitrogen Isotopes / blood,  diagnostic use
Predatory Behavior / physiology*
Seasons
Species Specificity
Spheniscidae*
Chemical
Reg. No./Substance:
0/Carbon Isotopes; 0/Nitrogen Isotopes

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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