Experimental Evidence for the Amelioration of Shadow Competition in an Orb-Web Spider Through the 'Ricochet' Effect

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.