Effects of vegetation structure and edge habitat on the density and distribution of white-footed mice (Peromyscus leucopus) in small and large forest patches

Abstract

We tested the hypothesis that if the quality or quantity of vegetation in small forest patches is greater than in large patches, then vegetation attributes may contribute to greater densities of white-footed mice (Peromyscus leucopus) in smaller patches. We trapped more mice per hectare in small (range 5–9 ha) than in large (range 110–150 ha) patches, as has been reported by other investigators. The difference appeared to be due primarily to the disproportionately high densities of P. leucopus in the edge habitat of small patches. While the greater edge-to-interior ratio in small patches could contribute to greater overall densities of mice in small patches, we trapped the same relative amount of edge and interior habitats in each of the six study patches. The structural complexity of understory vegetation was much greater in small than in large patches and also in edge than in interior habitats across the six patches. Thus, we trapped the most mice in the most structurally complex vegetation (i.e., edges of small patches). However, while vegetation at the edge of large patches was more complex than in the interior, we did not capture relatively high densities of P. leucopus in edge habitat of large patches. Hence, understory vegetation may differentially influence the distribution of P. leucopus between edge and interior habitats in forest patches of different sizes.

Annual Variation in Habitat Use by White-footed Mice, <em>Peromyscus leucopus</em>: The Effects of Forest Patch Size, Edge and Surrounding Vegetation Type

“…However, we did not find that movements from exterior to the edge or interior habitats were greater in smaller than larger patches in this study. If smaller and larger forest patches do not vary in emigration and immigration rates, as our data suggest, then a second possibility is that other factors, such as greater food abundance or cover from predators, may have resulted in greater abundances of mice in smaller patches or in particular the edges of small patches (Nupp and Swihart 1996;Diaz et al 1999;Anderson et al 2003;Anderson and Meikle 2006). A third possibility is that lower densities in larger patches may be the result of mice dispersing to low density regions within the heterogeneous forest patch to alleviate high densities, with fewer sites likely present in smaller forest patches (Krohne and Burgin 1990;Krohne and Hoch 1999).…”

“…The eight traps inside the forest patch were considered "interior" traps. Based on our previous findings (Anderson et al 2003) and corroborated by Burke and Nol (1998), the width of the edge habitat was defined based on typical edge floristic features. The surrounding habitat type in the exterior matrix was either pasture or corn fields (Table 1).…”

“…Studies have shown that populations of P. leucopus, unlike birds, insects, and most other mammals, have greater densities in smaller forest patches (Nupp and Swihart 1998;Krohne and Hoch 1999;Anderson et al 2003). One proposed mechanism to account for this negative density-area relationship is that habitat quality is lower in the exterior matrix than in woodland sites (Nupp and Swihart 1996;Krohne and Hoch 1999).…”

“…In contrast, investigators have found a consistent negative relationship between density of the White-footed Mouse (Peromyscus leucopus Rafinesque), a forest habitat generalist, and forest patch area Swihart 1996, 1998;Krohne and Hoch 1999;Mossman and Waser 2001;Schmid-Holmes and Drickamer 2001;Anderson et al 2003;Anderson and Meikle 2006). Although resource availability may influence population dynamics of small mammals (e.g., Nupp and Swihart 1996), there are other factors that may be responsible for the negative density-area relationship.…”

“…Some investigators have reported greater densities of Peromyscus spp. near edges (Cummings and Vessey 1994;Boyne and Hobson 1998;Manson et al 1999) (Cummings and Vessey 1994;Anderson et al 2003). In contrast, others have found fewer mice and lower maternal survival and litter success in edge habitats, presumably because parasitism, predation and interspecific competition can be higher along edges (Matter et al 1996;Morris and Davidson 2000;Batzli 2001, 2004).…”