Meeting Abstract
Individuals in the vast majority of known spider species are either solitary or cluster into groups of webs. Because only a few species demonstrate facultative aggregation, where individuals choose between solitary and group living, these systems are ideal for investigating the factors that influence the trade-offs of aggregating. We examined the costs and benefits associated with clustering in Nephila clavipes and hypothesized that tradeoffs would vary with a spider’s ontogenetic stage. Our study was conducted at the Firestone Center for Restoration Ecology, Baru, Costa Rica in the summer of 2014. We measured the cephalothorax width and web diameter of 400 spiders, and daily assessed the number of prey, males, and kleptoparasites in the web, web condition, the number of legs on the resident spider and its ultimate fate. Comparing clustered versus solitary spiders within each size class, we found that medium clustered and medium solitary spiders did not differ in any variable measured. However, small clustered spiders captured less small prey and less prey overall, but had ower depredation rate and longer web tenure than small solitary spiders. Finally, small spiders were more likely than expected to be clustered, while medium spiders were less likely than expected to be clustered. The data support the idea that the tradeoffs of clustering vary with the spider’s ontogenetic stage. Small spiders traded lower prey capture potentially for increased protection from predation. While the data revealed no tradeoffs for medium spiders, these spiders were more likely to be solitary, which may indicate a hidden cost. Variation present in the data among previous study years suggests that predation risk may drive clustering behavior, and merits further inquiry.
