Optimal foraging when predation risk increases with patch resources: an analysis of pollinators and ambush predators

Pollinators and their predators share innate and learned preferences for high quality flowers. Consequently, pollinators are more likely to encounter predators when visiting the most rewarding flowers. I present a model of how different pollinator species can maximize lifetime resource gains depending on the density and distribution of predators, as well as their vulnerability to capture by predators. For pollinator species that are difficult for predators to capture, the optimal strategy is to visit the most rewarding flowers as long as predator density is low. At higher predator densities and for pollinators that are more vulnerable to predator capture, the lifetime resource gain from the most rewarding flowers declines and the optimal strategy depends on the predator distribution. In some cases, a wide range of floral rewards provides near-maximum lifetime resource gains, which may favor generalization if searching for flowers is costly. In other cases, a low flower reward level provides the maximum lifetime resource gain and so pollinators should specialize on less rewarding flowers. Thus, the model suggests that predators can have qualitatively different top-down effects on plant reproductive success depending on the pollinator species, the density of predators, and the distribution of predators across flower reward levels.