Predator-prey interactions are often behaviorally sophisticated games in which the predator and prey are players, the value of prey behavior depends on the characteristics of the predator, and the value of predator behavior depends on the characteristics of the prey. Thus, changes in one player’s behavior may strongly affect the behavior of the other players in the system. Past studies teach us that hungrier prey take higher risks when foraging and that hungrier predators increase their foraging activity and are willing to take higher risks of injury. Yet, what happens when predator and prey can respond to each other simultaneously? We investigated the state game between predators and their prey by simultaneously manipulating the state of barn owls, Tyto alba, and their prey, Gerbillus andersoni allenbyi, in a large outdoor vivarium containing seed trays as resource patches for the gerbils.

Results/Conclusions

The owls significantly increased their activity when hungry. However, contrary to our predictions, they did not respond to changes in the state of the gerbils. The gerbils reacted strongly both to their own state, as well as to the owls’ state. In the presence of a hungry owl, the gerbils left more food in the resource patches, were less efficient in searching for food, and spent less time husking seeds in the food patches. The gerbils also left more food in the resource patches when they were well fed,  mostly dramatically when a hungry owl was present, i.e., when the risk was greater. Our study shows that predator-prey interactions give rise to a complex state game in which changes to the state of any of the players have important ecological consequences.