Risk and cost of immobility in the presence of an immobile predator

Abstract

Escape latency theory models the tradeoff between maintaining crypsis by remaining immobile near an immobile predator versus moving to flee or engage in fitness-enhancing activities. The model predicts that latency to flee increases as cost of fleeing increases and decreases as cost of remaining immobile increases. As predation risk increases, cost of fleeing, primarily due to abandoning crypsis due to immobility, decreases. Predictions have been tested for few risks and a single cost of immobility factor in only two species of active foragers. To gauge the breadth of applicability of the model, we tested effects of four risk factors and two cost of immobility factors in ambush-foraging phrynosomatid lizards, which we selected for testing because foraging mode strongly affects many aspects of ecology and behavior of lizards. Latency to flee decreased as standing distance (predator–prey distance before fleeing) decreased, predator approach speed increased, directness of approach increased, and predator persistence increased. Latency to move was shorter in the presence of food and shorter for males in the presence of females. Lizards often moved toward food or females instead of fleeing. Latency was affected as predicted by all risk and by cost of remaining immobile factors. Our findings agree with previous results for the same four risk factors and the foraging cost of immobility. That social cost of immobility affects latency as predicted is a novel finding. The model is robust, applying to ecologically diverse prey and to a wide range of factors affecting costs of fleeing and of immobility.