| In an attempt to avoid being eaten, prey individuals engage in anti-predator behavior, which should reduce predation rates, but also should decrease prey productivity and increase starvation. I used simple theoretical systems to examine how anti-predator behavior should influence prey populations and communities. In the first chapter, I used the Lotka-Volterra system of equations to show that anti-predator behavior can generate stability in such systems, but that a background rate of decrease is important to the qualitative and quantitative stability. In the second chapter, I used stochastic-dynamic programming to show that consumers need more accurate estimates of predation risk as a reproductive event approaches; when the length of time until the reproductive event is great, foragers can make considerable errors in estimates of predation risk without suffering substantial consequences. In the third chapter, I examined three systems of differential equations with differing relationships between anti-predator behavior and prey resource acquisition and found that, under fixed population densities, the non-lethal effect of predators should be greatest under high predation risk but moderate resource availability, while the lethal effect of predators should be greatest under moderate predation risk but high resource availability. Under equilibrium conditions, however, neither the non-lethal nor lethal effects of predators are a function of prey encounter rates with predators. However, the non-lethal effect, but not the lethal effect, always increases with resource availability. In the last chapter, I show that when two competitors with anti-predator behavior share a predator and a resource, coexistence of those competitors requires a trade-off between the competitors' encounter rates with either the predator or the resource, and the efficiency of the anti-predator behavior. |
