Predatory Behaviour is Plastic According to Prey Difficulty in Na⟨ve Spiderlings

Predatory behaviour is plastic towards different prey. However, prey differ in their defenses and predators should adjust in order to successfully subdue it. The variation in predatory behaviour could be either innate or developed from experiences. A feasible way to tease these factors apart is by studying inexperienced individuals. Here, I tested if the behaviour of inexperienced predators is different towards two prey types and if it correlates with the behaviour of the prey. I fed na < ve spiderlings of the sheet weaver cellar spider Physocyclus globosus (Pholcidae) with either fruit flies or ants as prey (potential extremes in difficulty). I found that, regardless of prey type, individuals that exhibited active defensive behaviour (longer time twisting, moving legs and body segments) elicited a more intense predatory behaviour by the spiderlings (longer time touching and wrapping the prey, and giving more bites). Ants were often more difficult prey than flies, even damaging the spiderling's leg in five trials. A successful attack to difficult prey was associated with increased handling time of additional silk needed to immobilize it. The differences in the predatory behaviour showed by P. globosus spiderlings suggest plasticity since their first attack. This plasticity would be adaptive for na < ve predators of any taxa that encounter a wide diversity of prey.