Effects of habitat disturbance on a Peromyscus leucopus (Rodentia: Cricetidae) population in western Pennsylvania

Many species of wild mammals occur in habitats that have been disturbed by fragmentation or degraded in quality. Previous researchers have hypothesized that demographic characteristics of populations may shift with changes in environmental conditions, with self-regulatory ability increasing with environmental suitability. We studied responses of white-footed mice (Peromyscus leucopus) to habitat disturbance. Given that optimal habitat for this species is deciduous woodland, we predicted that populations in habitats disturbed by cutting woody vegetation would be lower and more variable in density than in undisturbed habitat, density and stability of populations in disturbed habitat would increase over time, survival would be higher in undisturbed than in disturbed habitat, and populations in undisturbed habitat would show a greater degree of self-regulation. This 6-year study in western Pennsylvania involved 3 replicated study sites (each 3.8 ha), with woody vegetation removed on half of each site prior to beginning the study. Density in disturbed treatment averaged 65% of density in undisturbed habitat. There were no differences between treatments in survival or in population growth rates over time. Population trends over time were similar between treatments, populations in disturbed habitat did not become more stable with time, and density did not converge with that of undisturbed habitat. Although populations in the undisturbed habitat were clearly self-regulating, those in disturbed habitats were not. Despite expectations that demographic performance will align with environmental suitability, it may be difficult to ascribe a particular demography to a habitat generalist such as P. leucopus.