Document Detail

Behavioral and energetic costs of group membership in a coral reef fish.
MedLine Citation:
PMID:  17713786     Owner:  NLM     Status:  MEDLINE    
Animals in social aggregations often spend more time foraging than solitary conspecifics. This may be a product of the relative safety afforded by aggregations: group members can devote more time to foraging and less time to antipredator behaviors than solitary animals (the "risk reduction" effect). All else being equal, risk reduction should result in higher food intake for grouped animals. However, intragroup competition may force group members to spend more time foraging in order to obtain the same food ration as solitary individuals (the "resource competition" effect). We compared these opposing explanations of foraging time allocation in a coral reef fish, bluehead wrasse (Thalassoma bifasciatum). Aggregations of juvenile bluehead wrasse experience safety-in-numbers, and preliminary observations suggested that juveniles in aggregations spent more time foraging for copepods in the water column than solitary juveniles. However, the risk reduction and resource competition hypotheses are indistinguishable on the basis of behavioral observations alone. Therefore, we collected behavioral, dietary, and growth data (using otolith growth rings) for bluehead wrasse at multiple reefs around a Caribbean island. Despite spending more time foraging in the water column, grouped fish did not capture more prey items and had slower growth rates than solitary fish. Thus, the increased foraging time of grouped fish appears to reflect resource competition, not risk reduction. This competition may limit the size and frequency of aggregations among juvenile bluehead wrasse, which have been shown to experience reduced mortality rates in larger groups. Bluehead wrasse recruits also spent less time foraging but grew faster at sites where planktonic copepod prey were more abundant. This suggests the possibility that large-scale spatiotemporal variability in the abundance of planktonic copepods over coral reefs may produce corresponding variability in the dynamics of reef fish populations.
J Wilson White; Robert R Warner
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2007-08-23
Journal Detail:
Title:  Oecologia     Volume:  154     ISSN:  0029-8549     ISO Abbreviation:  Oecologia     Publication Date:  2007 Nov 
Date Detail:
Created Date:  2007-11-08     Completed Date:  2008-03-27     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0150372     Medline TA:  Oecologia     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  423-33     Citation Subset:  IM    
Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
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MeSH Terms
Behavior, Animal / physiology*
Energy Metabolism / physiology*
Feeding Behavior / physiology
Gastrointestinal Contents
Perciformes / growth & development,  physiology*
Social Behavior*
Time Factors
Virgin Islands of the United States

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