Of Moths and Mice: The Influence of Dispersal Distance and Local Predation Risk on Persistence of a Sparse Prey

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Of Moths and Mice: The Influence of Dispersal Distance and LocalPredation Risk on Persistence of a Sparse PreyClive G. Jones, Brett J. Goodwin, Richard S. Ostfeld and Eric M. Schauber.Predators can potentially exterminate populations of their prey. Understanding how prey populations persist in the face of predation can help us sustain populations of endangered species and control pest populations. For example, gypsy moths are introduced insect pests that cause much damage in hardwood forests of eastern North America. White-footed mice, which are abundant in these forests, are voracious predators on gypsy moth pupae and are capable of driving moths locally to extinction. Since moth extinction has not actually happened over larger areas, how do moths persist in the face of intense predation by mice? The combined effects of two factors are important: (1) the likelihood of a gypsy moth pupa being attacked varies from place to place and (2) gypsy moth caterpillars do not disperse very far during their lifetimes. Computer simulations indicate that combining these two factors can substantially increase the chances that moth populations will persist. During this project, data will be collected in oak forests in New York State that will allow the development, refinement and testing of these simulation models. The dispersal distances of gypsy moth caterpillars and the predation risk for gypsy moth pupae at several sites will be measured. These measurements will be incorporated into the computer simulation to predict how changing the spatial pattern of predation risk would affect gypsy moth populations. Finally, predictions will be tested in areas where there are different numbers of dispersing moth caterpillars by putting out feeding stations to manipulate the patterns of mouse foraging. This procedure will alter the risk of predation for gypsy moth pupae and should change the likelihood of local moth population persistence in a predictable way.