Size-dependent predation risk in cryptic prey

Visual crypsis of prey is determined by the interaction between an individual’s physical appearance to their predators and visual aspects of their environment. Physical size will impact visual appearance and thus potentially influence crypsis. However, research on this topic is limited, leaving the effect of size in cryptic prey largely unexplored. To identify if the success of cryptic phenotypes is size-dependent, we conducted a series of field experiments in which we exposed two types of cryptic artificial prey (uniform colored and disruptively patterned) of different sizes to free-living avian predators and recorded attack rate. Despite similar statistical power and methodology, we found increasing predation risk with increasing size only for disruptive phenotypes. Our results suggest that large sizes may break down ability for disruptive patterns to effectively break up the body outline. However, further research in more controlled conditions would be needed to distinguish the effects of initial detection and post-detection preferences on attack rates.