Effects of predation, fire, and supplemental feeding on populations of two species of Peromyscus mice

Food resources and predation play important roles in determining small mammal population dynamics. These factors also can interact as individuals under predation pressure make trade-offs between access to food resources and exposure to predators. Fires consume food sources and reduce cover, which increases exposure to predators. For species that occur in areas with frequent fire, it is instructive to consider how all of these factors interact to affect populations of interest. We examined how supplemental feeding, mammalian predator exclusion, and prescribed fire affected survival, abundance, and reproduction of cotton mice (Peromyscus gossypinus) and oldfield mice (P. polionotus) in a longleaf pine ecosystem. Burning and predator exclusion interacted to affect survival of cotton mice; survival was similar in predator exclosures and controls in nonburning periods and in controls following prescribed burns but increased in exclosures following burns. Rates of transitions to reproductive states (which for females includes lactation or gravidity and for males, descent of testes) decreased in burn years but increased with the combination of feeding and predator exclusion. Supplemental feeding increased abundances. Among oldfield mice, survival and abundance were greater in predator exclusion areas than in controls. Supplemental feeding and the interaction of feeding and predator exclusion also increased abundances. During peak breeding seasons during which burning occurred rates of transitions to reproductive states declined to such an extent that reproductive transition rates in these seasons were lower than during nonpeak breeding seasons.