The complexity of site quality: multiple factors affect web tenure in an orb-web spider

Abstract

Behavioural decisions involving foraging, mate choice and habitat selection are complex and difficult to evaluate experimentally. Web abandonment by orb spiders is a complex decision that is experimentally tractable. For females of the golden orb spider, Nephila clavipes, the web is a microhabitat that serves as a prey capture device, a mating site and a habitat for parasites. Thus, the web embodies the complexity of a bird territory or mammal home range, but is spatially compact and amenable to experimental manipulation. We used both field census data and field experimental manipulations to address the importance of prey capture rate, kleptoparasite load and male presence for web tenure (the time spent at a web site) in both mature and immature female N. clavipes. No factor explained variation in web tenure for immature females, although census data suggested that increased kleptoparasite load decreased web tenure. For mature females, increased male presence decreased web tenure, while increased prey capture rate, condition and body size all increased web tenure. Web tenure also decreased over the course of the season. Females integrate multiple cues to make web movement decisions. One of these cues is male presence, which detracts from the quality of a web site, suggesting that mate harassment might affect females' web movement decisions. Insight into this seemingly simple behaviour contributes to a growing understanding of how and when animals integrate multiple cues into behavioural decisions.