© 1996 by The Society for Integrative and Comparative Biology
Risk Sensitivity and the Paradox of Colonial Web-Building in Spiders1
Department of Biological Sciences, University of Cincinnati Cincinnati, Ohio 45221-0006
Group foraging is rare in spiders, occurring only where prey availability is high. If colonial web-building increases individual prey capture rates as shown, why does group foraging not occur more often where prey are scarce? Risk sensitivity may explain this paradox, as variance in prey capture is reduced in groups; risk-averse spiders should join groups only when prey exceed a threshold level. Field studies show that group foraging varies as predicted between species, between populations of a single species, and between sites within a population. However, recent models suggest the necessity of examining variance within individuals over time rather than between individuals within populations. Additionally, mechanisms responsible for variance reduction in colonial webs may be less effective than previously assumed. New field data suggest that while prey variance over time may be somewhat less for individual spiders in groups than for solitaries, the relationship between colonial web-building and variance in prey capture is far more complex than originally thought. The influence of risk sensitivity on reproductive success and the evolution of colonial web-building is discussed.