Shadow competition and the evolution of sensory capability in sit-and-wait predators

Shadow competition occurs when an organism prevents another organism's access to a resource by intercepting that resource first, thereby casting a ``shadow'' over the competing organism. This competition is commonly seen in the case of sit-and-wait (or ambush) predators. Shadow competition is closely related to the sensory capabilities of the organism, such as the range at which a predator can detect prey as well as the field of view of prey detection. Here, we develop an agent-based model whereby stationary, sit-and-wait predators exert shadow competition for prey on other predators on an explicit spatial landscape. Four predator characteristics can evolve: location, orientation, sensory radius, and field of view. We vary the number of available prey, the location of the prey source, the cost of sensory perception, and the energy requirements of the predator to find how shadow competition affects the evolved predator characteristics. We find that predators evolve a long, narrow sensory cone as a result of shadow competition, and that shadow competition greatly limits the efficiency of the predator-prey system. Thus, shadow competition, and the spatial interaction of predators in general, can dramatically shape predator phenotype and behavior.