Stability and Prey Behavioural Responses to Predator Density

(1) Earlier models of mutual interference between searching predators or parasites ignored the potentially important effects of prey behavioural responses to predators. (2) A model incorporating simple prey behavioural responses shows that prey availability may either increase or decrease as a function of predator density. Thus both mutual interference and enhancement are possible depending upon the behaviour of the prey. (3) The importance of prey behavioural responses are demonstrated in a laboratory study using an aquatic insect predator with both mobile and immobile prey. Two specific behaviours, spacing and movement, are shown to affect the predation rate. Movement of prey is also related to predator density in a predicted fashion. (4) The stability properties of a Lotka-Volterra system incorporating prey escape responses are discussed. The system is stable if prey responses result in relatively mild interference. Prey responses are destabilizing if they result in mutual enhancement or in interference that is so strong that the attack rate of the entire predator population decreases with increasing predator density. (5) Set in an evolutionary context, the behaviour of notonectids suggests that avoidance of cannibalism may have a larger effect on fitness than maximization of feeding efficiency.