Meeting Abstract
Although the vast majority of spiders are solitary, several species are strictly colonial, while others, such as the orb weaver Nephila clavipes, variably aggregate or remain solitary. These latter species can provide insights into the conditions favoring social behavior in spiders. We have found that clustering in N. clavipes is generally most favorable for small spiders, which have reduced predation rates if clustered than if solitary, but that temporal variation in predator and prey abundance correlate with the trade-offs and frequency of clustering. In this study we documented the formation of clusters in N. clavipes, testing the prediction that small spiders should drive cluster formation, particularly in years when predators are abundant. Assuming groups provide protection, spiders experiencing a previous predation attempt might also be motivated to cluster. We assessed how spider size and leg autotomy related to the order in which spiders moved into and out of a cluster. We observed 400 webs in each of three years, finding that in the year of highest predation, small spiders were three times more likely to create a two-spider cluster than were medium spiders, but that small and medium spiders left clusters with the same frequency. We discuss variation among the study years and implications for the evolution of social behavior in spiders.
