Annual changes in structural complexity of understory vegetation and relative abundance of Peromyscus leucopus in fragmented habitats

Greater structural complexity of understory vegetation may be one factor that contributes to the negative relationship between density of generalist rodents (eg, Peromyscus leucopus Rafinesque, 1818) and forest patch area; however, this hypothesis is difficult to test. We removed the problem of multi-collinearity among variables by analyzing changes in structural complexity and relative abundance of P. leucopus in 15 forest patches (1.3-200 ha) over a 3-yr period. We found that an increase in the relative abundance of P. leucopus was associated with an increase in structural complexity of understory vegetation in the same patches between years. Structural complexity of the understory was greater in smaller forest patches which we speculate may be influenced by moisture. It is possible that understory vegetation provides greater food availability and/or cover from some predators in small patches, but the specific mechanism(s) remains unclear. Multiple factors can potentially influence populations of P. leucopus, but our results provide strong evidence that structural complexity of understory vegetation positively influences relative abundance of P. leucopus in fragmented habitats.