THE EFFECT OF ADAPTIVE ANTIPREDATOR BEHAVIOR ON EXPLOITATIVE COMPETITION AND MUTUALISM BETWEEN PREDATORS

We investigate the effect of changing the population size of one predator species on the fitness of another predator when both share a common prey species. The prey is assumed to have different anti-predator behaviors for each predator. Anti-predator behavior can result in one or both predators having positive effects on the fitness of the other. Positive short-term effects (on a behavioral time scale) can be produced by three mechanisms: (1) A behavior that defends against one predator may make the prey more vulnerable to the other; (2) Increased defensive behavior against one predator may increase the cost of defense against the other, resulting in a reduction in the latter defense; (3) If the prey constantly employs some anti-predator behavior, an increase in one behavior can only come at the expense of a reduction in another. The long-term effect of one predator on another is more likely to be negative than is the short-term effect, due to reduction in prey density. However, a strongly positive short-term effect and a prey population that is weakly affected by predator density, can produce a positive long-term effect. Even when both short- and long-term interactions between predators are competitive, the prey's behavior often reduces the ratio of inter- to intra-specific competition between the two predators, promoting their coexistence.