Abstract :
To examine the role of individual variation in the dynamics of group formation, I conducted a mark-recapture study and a series of laboratory and field experiments with Holocnemus pluchei spiders (Araneae: Pholcidae). These spiders can either share webs or live alone, and individuals shift frequently between these strategies. Spidersʹ decisions were influenced by size and recent feeding success. In the laboratory, small hungry spiders introduced into a web that held a larger conspecific resident were more likely than small well-fed spiders to abandon the web and build their own web. This behaviour pattern gradually reversed as spiders grew: large hungry spiders were more likely than large well-fed spiders to stay in the shared web. When I introduced spiders into empty webs, they were more likely to stay compared with spiders tested with conspecifics. However, hunger level also influenced behaviour even when conspecifics were not present. Food-deprived spiders were more likely to abandon webs and build their own, consistent with the idea that spiders were following a winstay/lose-shift strategy. In the field, spiders were more likely to stay in webs overnight when they were given supplemental food. In another experiment, spiders that were found building webs in cleared areas were smaller and thinner than average. Finally, I tested whether the size of the intruder or the resident affected whether spiders joined webs. Large intruders were more successful at remaining in webs than smaller intruders, although spiders of all sizes had some success in joining groups. Additional synthetic theoretical work is needed to integrate the complex processes underlying the formation and persistence of groups.
