Experimental Evidence for the Amelioration of Shadow Competition in an Orb-Web Spider Through the ‘Ricochet’ Effect
Department of Biological Sciences, Macquarie University, North Ryde, Sydney, NSW, Australia
Stationary predators such as spiders can face competition from conspecifics simply by virtue of the spatial positioning of their webs. Shadow competition, wherein a predator ‘upstream’ restricts access to prey for another individual further ‘downstream’, can affect the foraging success of stationary predators. However, in spiders that build orb-webs in proximity to each other, insect prey often ‘ricochet’ off the outer web and land on the inner web. In this study, I asked whether the negative effect of shadow competition could be compensated for by the ricochet effect. I experimentally show that despite a strong spatial advantage to a spider on the outer side in terms of prey interceptions, the likelihood of prey intercepting the inner web is increased through the ricochet effect. I also show that the degree of overlap between the webs significantly influences both the number of prey intercepted as well as the number of ricochets. This study shows experimentally that a spider that builds its web close to a conspecific’s web suffers very little cost in terms of lost prey interception.