Top-down pulses reduce prey population sizes and persistence

Resource pulses are well documented and have important consequences for population dynamics relative to continuous inputs. However , pulses of top-down factors (e.g. predation) are less explored and appreciated in the ecological literature. Here , we use a simple differential equation population model to show how pulsed removals of individuals from a population alter population size relative to continuous dynamics. Pulsed removals result in lower equilibrium population sizes relative to continuous removals , and the differences are greatest at low population growth rates , high removal rates , and with large , infrequent pulses. Furthermore , the timing of the removal pulses (either stochastic or cyclic) affects population size. For example , cyclic removals are less likely than stochastic removals to result in population eradication , but when eradication occurs , the time until eradication is shorter for cyclic than with stochastic removals