Fast and accurate decisions through collective vigilance in fish shoals.
Although it has been suggested that large animal groups should make better decisions than smaller groups, there are few empirical demonstrations of this phenomenon and still fewer explanations of the how these improvements may be made. Here we show that both speed and accuracy of decision making increase with group size in fish shoals under predation threat. We examined two plausible mechanisms for this improvement: first, that groups are guided by a small proportion of high-quality decision makers and, second, that group members use self-organized division of vigilance. Repeated testing of individuals showed no evidence of different decision-making abilities between individual fish. Instead, we suggest that shoals achieve greater decision-making efficiencies through division of labor combined with social information transfer. Our results should prompt reconsideration of how we view cooperation in animal groups with fluid membership.
School of Biological Sciences, University of Sydney, Sydney, NSW 2006, Australia. ashleyjwward@gmail.com
Ashley J W
AJ
Ward
James E
JE
Herbert-Read
David J T
DJ
Sumpter
Jens
J
Krause
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D005399:Fishes / Q000502:physiology*
Philos Trans R Soc Lond B Biol Sci. 2009 Mar 27;364(1518):743-53
19073480
Proc Natl Acad Sci U S A. 2004 Nov 16;101(46):16385-9
15534225
Proc Natl Acad Sci U S A. 2009 May 12;106(19):7893-8
19416834
Biol Lett. 2007 Apr 22;3(2):137-9
17284400
Trends Cogn Sci. 2009 Jan;13(1):36-43
19058992
Curr Biol. 2008 Nov 25;18(22):1773-7
19013067
Anim Behav. 1999 Sep;58(3):537-543
10479369
Trends Ecol Evol. 2010 Jan;25(1):28-34
19735961
Theory Biosci. 2008 Jun;127(2):177-86
18458976
J Theor Biol. 2004 Jul 21;229(2):209-20
15207476
Proc Natl Acad Sci U S A. 2008 May 13;105(19):6948-53
18474860
Trends Ecol Evol. 2005 Apr;20(4):187-93
16701367
J Exp Biol. 2002 Dec;205(Pt 24):3833-44
12432007
Anim Behav. 2000 Feb;59(2):403-409
10675263
J Exp Biol. 2009 Jan;212(Pt 2):178-83
19112136