Cooperative capture of large prey solves scaling challenge faced by spider societies

A decrease in the surface area per unit volume is a well known constraint setting limits to the size of organisms at both the cellular and whole-organismal levels. Similar constraints may apply to social groups as they grow in size. The communal three-dimensional webs that social spiders build funct...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 105; no. 33; pp. 11818 - 11822
Main Authors Yip, Eric C, Powers, Kimberly S, Avilés, Leticia
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 19.08.2008
National Acad Sciences
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ISSN0027-8424
1091-6490
1091-6490
DOI10.1073/pnas.0710603105

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Summary:A decrease in the surface area per unit volume is a well known constraint setting limits to the size of organisms at both the cellular and whole-organismal levels. Similar constraints may apply to social groups as they grow in size. The communal three-dimensional webs that social spiders build function ecologically as single units that intercept prey through their surface and should thus be subject to this constraint. Accordingly, we show that web prey capture area per spider, and thus number of insects captured per capita, decreases with colony size in a neotropical social spider. Prey biomass intake per capita, however, peaks at intermediate colony sizes because the spiders forage cooperatively and larger colonies capture increasingly large insects. A peaked prey biomass intake function would explain not only why these spiders live in groups and cooperate but also why they disperse only at large colony sizes, thus addressing both sociality and colony size range in this social spider. These findings may also explain the conspicuous absence of social spiders from higher latitudes and higher elevations, areas that we have previously shown to harbor considerably fewer insects of the largest size classes than the lowland tropical rainforests where social spiders thrive. Our findings thus illustrate the relevance of scaling laws to the size and functioning of levels of organization above the individual.
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Present address: David Evans and Associates, 2100 River Parkway, Portland, OR 97201.
Present address: Department of Entomology, Cornell University, Ithaca, NY 14853.
Author contributions: K.S.P. and L.A. designed research; E.C.Y. and K.S.P. performed research; L.A. analyzed data; and E.C.Y. and L.A. wrote the paper.
Edited by Raghavendra Gadagkar, Indian Institute of Science, Bangalore, India, and approved June 16, 2008
ISSN:0027-8424
1091-6490
1091-6490
DOI:10.1073/pnas.0710603105