Northeastern Naturalist Vol. 22, No. 2 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 287 2015 NORTHEASTERN NATURALIST 22(2):287–298 Effects of Vegetation, Landscape Composition, and Edge Habitat on Small-Mammal Communities in Northern Massachusetts Eric S. Lindemann1, Jonathan P. Harris1, and Gregory S. Keller1,* Abstract - In southern New England forests, small mammals provide essential contributions to ecosystem functioning via food-web interactions and seed dispersal. This region has been exposed to extensive habitat fragmentation due to residential and agricultural development, resulting in a considerable amount of edge habitat, in addition to naturally occurring landscape heterogeneity. Limited research has been conducted relating smallmammal species richness and abundance to different types of edge habitat in this region. Studies incorporating an analysis of variation in both fine-scale vegetation and coarse-scale landscape variation are even more limited. We compared small-mammal richness, total abundance, and abundance of Peromyscus maniculatus (Deer Mouse), Peromyscus leucopus (White-footed Mouse), Myodes gapperi (Red-backed Vole), Tamias striatus (Eastern Chipmunk), and Tamiasciurus hudsonicus (Eastern Red Squirrel) at developed-edge, wetland- edge, and forest-interior sites. We also measured vegetation and landscape variables to understand how variation in characteristics at different scales affected small-mammal measures. We selected 4 sites of each edge type and used Sherman live-traps during the summers of 2009–2010 to survey small-mammal populations (75 traps for 4 nights at 12 sites for 2 y = 7200 trap-nights). We did not find differences among edge types and interior forest for total abundance, richness, and abundance of the 5 small-mammal species with sufficient data for analysis. However, vegetation variables and landscape variables were significantly associated with small-mammal populations. Step-wise linear regression included vegetation variables for 4 of the 5 species, and various landscape scales were included in all analyses except abundance of Peromyscus adults. Patch size was included in 4 analyses (positive for total abundance, White-footed Mouse, and Red-backed Vole; negative for Eastern Chipmunk). We found conifer basal area to have a positive relationship with abundance of Peromyscus adults and Red-backed Voles, but a negative relationship with abundance of Peromyscus juveniles and Eastern Red Squirrels. Species abundance and richness of small-mammal communities and populations in northeastern Massachusetts were related to both fine-scale vegetation differences and coarse-scale landscape metrics, but these relationships were complex and scale-dependent. Introduction Residential and agricultural development in southern New England has fragmented forests, resulting in more developed edges, less interior forest, and less habitat for area-sensitive and forest-interior species (Yahner 2000). In northern Massachusetts, forests are heavily fragmented by both historic agricultural development and current residential development. Edge creation from forest 1Department of Biology, Gordon College, Wenham MA 01984. *Corresponding author - greg.keller@gordon.edu. Manuscript Editor: Rosalind Renfrew Northeastern Naturalist 288 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 Vol. 22, No. 2 fragmentation results in increased sunlight penetration, more shrub-level and understory cover, and different food resources compared to the forest interior (Yahner 2000). Although edge habitats may appear similar, Yahner (1988) has suggested that they are not identical and require further study. Small mammals are important biological components of forest communities: they play a vital role in food-web interactions and as seed dispersers (e.g., Schmidt et al. 2001, Swengel and Swengel 1992, Verme 1957). Small-mammal populations may be negatively impacted by habitat fragmentation, which affects their movement patterns (Diffendorfer et al. 1995), foraging strategies (Orrock and Danielson 2005), population structure (Nupp and Swihart 2000), and reproductive output (Wilder and Meikle 2006). In turn, these impacts can alter species richness and abundance, community-level interactions, and food-web dynamics in the forests of Massachusetts. While extensive fragmentation effects may reduce small-mammal populations, influences are likely species specific, and resultant patterns may counter this more general reduction trend. For example, Nupp and Swihart (2000) found that although species richness was lower in smaller forest patches, abundance of Peromyscus leucopus (White-footed Mouse), a species they note to be commonly considered a habitat generalist and more abundant in smaller forest-patches, was not related to patch size. In Pennsylvania, Yahner (1992) found that abundance of White-footed Mice actually increased as fragmentation increased. Yahner also noted that abundance of Myodes gapperi (Red-backed Vole) was not associated with degree of fragmentation. Differences in habitat use based on edge type provide an additional consideration of fragmentation for these species. For example, Bayne and Hobson (1998) found that the types of habitat surrounding patches affected small-mammal abundance in agricultural edges but not silvicutural edges. They also reported that Peromyscus maniculatus (Deer Mouse) were more abundant in edge habitats compared to interior habitats. In contrast, in the highly fragmented region of east-central Illinois, Wolf and Baltzi (2002, 2004) found that White-footed Mouse was more abundant in forest-interior habitat compared to edges. These studies illustrate that habitat fragmentation results in varied patterns that are species specific and require both community-level and population-level analyses. In this study, we used live trapping to study the effects of fragmentation and natural landscape heterogeneity at multiple scales on small-mammal communities and populations. Our objectives were to: (1) compare differences in small-mammal richness, total abundance, and abundance of individual species at developed-edge, wetland-edge, and forest-interior habitats; and (2) determine how differences in vegetation structure and landscape-level fragmentation affected richness and abundance. Methods This study was part of a larger project on the effects of edge characteristics on terrestrial vertebrates in New England. Study areas were in public forests at Appleton Farms, Agassiz Rock Wilderness Area, Gordon College, and Long Hill Reservation Northeastern Naturalist Vol. 22, No. 2 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 289 in northern Essex County, MA. Sites were located within a 65-km2 area (center = 42.616997°N, 70.820145°W). Forests in this region are dominated by Quercus spp. (oak), Carya spp. (hickory), Pinus strobus L. (Eastern White Pine), with some Acer rubrum L. (Red Maple), Fagus grandifolia (Ehrh.) (American Beech), Tsuga canadensis (L.) Carr. (Eastern Hemlock), and Betula spp. (birch). We selected sites that were similar in vegetation, and gave preference to areas with oak and hickory overstory trees because of their potential importance as food resources. The region contains 48% forest, with numerous small ponds and vernal pools, emergent wetlands, extensive pasture and horse farms, and both historic and recent residential development. We selected 3 habitat categories for study: developed edge (forest abutting agricultural and residential development), natural-wetland edge (forest abutting wetland), and forest-interior habitat. Edge sites were in forest habitat centered within 20 m of the edge–canopy opening; interior sites were located at least 150 m from an edge. This distance, selected for a separate analysis of edge effects on avian communities, is greater than what is typically defined as interior forest for small mammals (Bayne and Hobson 1998, Mills 1995, Pardini 2004). Sites were at least 300 m apart to ensure independence. We selected 4 sites for each category, identified using ArcGIS 9.3 software and ground-truthing. We trapped small mammals between 30 May and 5 July in 2009 and 2010. At each site, we used 75 Sherman live-traps for 4 consecutive nights (Nupp and Swihart 2000), resulting in a total of 600 trap-nights per site and 7200 trap-nights total. We grouped sites that were spatially close to each other and randomly selected the order of trapping for each group. Within a group, we systematically ordered our trapping effort, and made sure that we trapped in sites from more than one habitat category at the same time to avoid temporal bias. Traps were set at 2–3 sites concurrently. At each site, we set 3 rows of 25 traps with traps ~3 m from adjacent traps. We baited traps with rolled oats mixed with peanut butter, provisioned them with cotton balls for warmth and cover, and checked them every morning. We marked individuals with ear tags; determined species, gender, and breeding condition; and recorded tail, body, ear, and foot length (Oxely et al. 1974). Repeat captures were not counted in survey totals. We released individuals at the point of capture immediately after processing and we collected any dead individuals as vouchers and submitted them to the Gordon College Museum of Natural History, Wenham, MA. We collected vegetation data during June–July 2009 at each site following a modified version of James and Shugart’s (1970) methods. In an attempt to reduce the number of correlated variables, we limited the large number of potential variables to those that might have biological significance to small mammals. Species composition of understory and overstory trees and shrubs were qualitatively similar among sites. We quantified vegetation within a 12-m radius circular plot centered at each site; edge-sampling plots were located 15 m into the forest from the edge. Within each plot, we counted the number of snags (>7.5 cm diameter at breast height [dbh], >1.5 m tall) and logs (>7.5 cm dbh, >25 cm long). We counted the number of overstory trees (>7.5 cm dbh, >1.5 m tall) and measured dbh of Northeastern Naturalist 290 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 Vol. 22, No. 2 coniferous and deciduous overstory trees to calculate total basal area separately for the 2 types. We counted the number of understory trees (<7.5 cm dbh, >1.5 m tall) and shrubs (less than 7.5 cm dbh, 0.5–1.5 m tall) along a 1 m x 12 m transect in each of the 4 cardinal directions from the center of the plot and measured percent leaf litter, percent herbaceous cover, and percent canopy cover with an ocular tube at 2-m intervals along the same transects, for a total of 20 points per plot. Using 2008 digital ortho quarterquads (DOQQs) from the Massachusetts Office of Geographic Information (http://www.mass.gov/mgis/massgis.htm), we calculated landscape metrics in ArcMap 9.3 (Environmental Systems Rsearch Institute, http://www.esri.com). We outlined circles 200, 500, and 1000 m from the center of each study site within which we delineated patches of forest and lengths of edges. We used the editing and measuring tools to outline feature classes and determine the extent of forest cover within each circle. We measured the total amount of forest (ha), total linear length (m) of developed edge, and total linear length (m) of wetland edge. We also outlined and calculated the forest-patch size in which study sites were located, defined as contiguous forest without breaks from roadways, power-line rights-of-way, or other natural or human-created openings. Analysis We compared vegetation variables, landscape variables, and mammal richness and abundance using ANOVA and posthoc Tukey’s test of pairwise comparisons for significant differences, with habitat categories (wetland edge, developed edge, and forest interior), year, and year*habitat category interaction as the independent variables. Dependent variables for mammal data included species richness (number of species documented at each site), total abundance (number of different individuals captured at each site for all species combined), and abundance of individual species with at least 8 different captures during both years combined. Given the difficulty of distinguishing the 2 Peromyscus species using morphological data in the field (Choate 1973, Rich et al. 1996), we also combined abundances of these 2 species to analyze at the genus level, and we analyzed Peromyscus adults and juveniles separately. Years (year, year*habitat category) were not significantly different from each other for all measures; therefore, we combined data from both years for subsequent analyses. We used forward stepwise regression (α = 0.15 to add or remove a variable) to assess effects of landscape and vegetation variables on small-mammal richness and abundance. Starting models included 4 independent landscape variables within each of 3 radii (200 m, 500 m, and 1000 m) from the center of each study site: patch size, percent forest, linear length of wetland edge, and linear length of developed edge. Independent vegetation variables were: density of snags, logs, shrubs, understory trees, overstory coniferous trees, and overstory deciduous trees; total basal area of overstory coniferous trees and deciduous overstory trees; overstory tree richness; and percent canopy cover, herbaceous ground cover; and leaf litter. For all analyses, α = 0.05, and we report trends for 0.05 < P < 0.10. We analyzed data using Minitab 14 (2002; State College, PA). Northeastern Naturalist Vol. 22, No. 2 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 291 Results Habitat categories differed in several vegetation and landscape metrics (Table 1). On average, wetland-edge sites tended to have greater canopy cover and deciduous basal area compared to other sites. Interior sites had greater tree richness, more deciduous trees, snags, and logs, and larger patch sizes than other habitat categories. Habitat categories differed at all landscape scales including 200-m developed edge and forest, 500-m developed edge, and 1000-m wetland edge. We captured a total of 9 small-mammal species during both years combined, including 115 different individuals of 8 species during 2009 and 119 different individuals of 8 species during 2010 (Table 2). Species with the highest number of captures included Deer Mouse, White-footed Mouse, Red-backed Vole, Red Squirrel (Tamiasciurus hudsonicus), and Eastern Chipmunk (Tamias striatus). We did not capture enough Glaucomys volans (Southern Flying Squirrel), Blarina Table 1. Average (± SE) values for vegetation and landscape metrics that differ significantly between developed-edge, wetland-edge, and forest-interior site categories in northeastern Massachusetts during the summers of 2009 and 2010. Values for habitats with different superscripted letters are significantly different (P < 0.05) from each other based on ANOVA and Tukey’s test of pairwise comparisons. Variable Developed edge Wetland edge Forest interior Tree richness (# species) 3.0 ± 0.5A 3.7 ± 0.2AB 4.8 ± 0.3B Canopy cover (%) 88.8 ± 2.8A 98.3 ± 1.1B 96.3 ± 2.5AB Deciduous density (# individuals) 9.8 ± 1.5A 13.0 ± 1.9AB 19.0 ± 2.3B Deciduous basal area 8291.0 ± 1174AB 4003.0 ± 594B 12,190.0 ± 2056A Snag density (# individuals) 2.0 ± 0.5A 2.0 ± 0.6A 5.0 ± 0.9B Log density (# individuals) 4.5 ± 1.0A 7.5 ± 0.9AB 12.5 ± 3.0B Patch size (ha) 16.4 ± 3.5A 89.1 ± 36.7A 117.4 ± 18.6B Developed edge (m) within 200 m 661.0 ± 116A 148.0 ± 40B 224.0 ± 85B Forest area (ha) within 200 m 8.3 ± 0.4A 10.4 ± 0.4A 6.8 ± 0.7B Developed edge (m) within 500 m 5052.0 ± 490A 2015.0 ± 471B 2355.0 ± 492B Wetland edge (m) within 1000 m 4557.0 ± 211A 6204.0 ± 520AB 7048.0 ± 972B Table 2. Total number of new captures of each species documented during the summers of 2009/2010 in 3 habitat categories (developed edge, wetland edge, and forest interior; 4 sites within each type and total of 7200 trap-nights) in northeastern Massachusetts. Species Developed edge Wetland edge Forest interior Blarina brevicauda Say (Short-tailed Shrew) 3/0 0/0 1/0 Sorex cinereus Kerr (Masked Shrew) 0/0 0/0 1/3 Peromyscus leucopus Rafinesque (White-footed Mouse) 4/4 11/11 5/14 Peromyscus maniculatus (Wagner) (Deer Mouse) 26/24 24/11 17/16 Peromyscus juveniles 13/13 12/9 8/10 Peromyscus adults 17/15 23/13 14/20 Myodes gapperi (Vigors) (Red-backed Vole) 2/0 8/11 2/2 Tamiasciurus hudsonicus Erxleben (Red Squirrel) 0/2 4/5 2/6 Tamias striatus L. (Eastern Chipmunk) 1/4 0/2 0/1 Glaucomys volans L. (Southern Flying Squirrel) 3/0 1/0 0/1 Mustela frenata Lichtenstein (Long-tailed Weasel) 0/0 0/1 0/0 Northeastern Naturalist 292 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 Vol. 22, No. 2 brevicauda (Northern Short-tailed Shrew), Sorex cinereus (Masked Shrew), or Mustela frenata (Long-tailed Weasel) individuals to allow further species analyses. We found no significant difference among the 3 habitat types for species richness (F2, 21 = 0.03, P = 0.97) or total abundance (F2, 21 = 0.56; P = 0.58) (Fig. 1). Furthermore, species-abundance patterns did not differ based on habitat type, although the number of captures of White-footed Mouse averaged 2 individuals less and Deer Mouse 2 individuals more at developed-edge sites compared to other habitats (Fig. 2). Red-backed Voles were found almost exclusively at wetland-edge sites (mean = 2.3 ± 1.3), but among-site variation was high. Both vegetation and landscape characteristics were associated with smallmammal variables (Table 3). Species richness and abundance were not associated with vegetation metrics; however, abundance of 4 of the 5 species we analyzed separately, as well as the composite Peromyscus adults and Peromyscus juveniles, responded to vegetation measures. Abundance of Peromyscus adults and Red-backed Voles were positively related to conifer basal area, Deer Mouse abundance was higher where leaf litter was lower, and Eastern Chipmunk abundance was lower where tree richness was higher. Eastern Red Squirrel abundance was positively related to closed-canopy conditions with low shrub-density and low coniferous basal area. Peromyscus juvenile abundance was positively related to shrub density and conifer density; in contrast, Peromyscus adult abundance was associated with lower conifer basal area. Landscape-level metrics were included in regression models for each analysis except Peromyscus adult abundance (Table 3). Patch size was positively associated Figure 1. Average (+ SE) richness (P = 0.97) and abundance (P = 0.58) of small mammals at 4 developed-edge, 4 forest-interior, and 4 wetland-edge sites in northeastern Massachusetts during summer 2009–2010 (years combined; total of 7200 trap-nights). Northeastern Naturalist Vol. 22, No. 2 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 293 Figure 2. Average (+ SE) abundance of Peromyscus leucopus (White-footed Mouse) (P = 0.11), Peromyscus maniculatus (Deer Mouse) (P = 0.42), Myodes gapperi (Red-backed Vole) (P = 0.15), Tamias striatus (Eastern Chipmunk) (P = 0.19), and Tamiasciurus hudsonicus (Eastern Red Squirrel) (P = 0.44) at 4 developed-edge, 4 forest-interior, and 4 wetland-edge sites during the summers of 2009 and 2010 (years combined; total of 7200 trap-nights). P-values illustrate results from ANOVA comparisons among habitats. Table 3. Significant differences (P < 0.05) and trends (0.05 < P < 0.10) between small-mammal richness, total abundance, and individual abundance relative to vegetation and landscape variables from forward step-wise regression during the summers of 2009 and 2010 in northeastern Massachusetts. The R2 value represents the overall regression equation. The - and + symbols before variables indicate the direction—negative and positive, respectively—of the regression relationship. Variable R2 Vegetation (P-value) Landscape (P-value) Richness 19.7 - 500-m wetland edge (0.03) Abundance 59.2 + Patch size (0.02) - 200-m forest (0.02) + 500-m developed edge (0.004) - 1000-m developed edge (0.04) Peromyscus adults 16.0 + Conifer basal area (0.05) Peromyscus juveniles 66.4 + Shrub density (0.004) + 500-m developed edge (0.08) - Conifer basal area (0.007) + Conifer density (0.04) P. leucopus 32.6 + Patch size (0.03) + 200-m wetland edge (0.05) P. maniculatus 45.0 -% leaf litter (0.13) + 500-m developed edge (0.03) + 1000-m forest (0.02) Myodes gapperi 96.1 - Deciduous density (less than 0.001) + Patch size (less than 0.001) + Conifer basal area (0.04) - 500-m wetland edge (0.03) + 500-m developed edge (0.004) Tamias striatus 21.3 - Tree richness (0.12) - Patch size (0.06) Tamiasciurus hudsonicus 53.0 + Canopy cover (0.007) - Conifer basal area (0.03) - Shrubs (0.07) - 200-m forest (0.001) Northeastern Naturalist 294 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 Vol. 22, No. 2 with total abundance and White-footed Mouse and Red-backed Vole abundance, but negatively associated with abundance of Eastern Chipmunk. Species-abundance patterns illustrated associations with various scales of landscape-level metrics. For example, White-footed Mice were associated more with wetland-edge habitat at 200 m, and Deer Mice and Peromyscus juveniles were more abundant when there was more linear developed-edge within 500 m. Deer Mouse abundance was higher where there was more forested area within 1000 m. Red-backed Vole abundance was greater when there was more developed edge but lower when there was more wetland edge within 500 m. Both total small-mammal and Eastern Red Squirrel abundance were associated with less forest within 200 m. Discussion We expected that the natural heterogeneity and high productivity associated with natural wetland edges would support greater richness and abundance of small mammals compared to developed edges. Furthermore, we hypothesized that vegetation differences associated with interior forest also would lead to greater richness and abundance relative to developed edges. Our data, however, did not support these hypotheses. We found evidence of community-level and population-level responses to both coarse-scale (landscape) and fine-scale (vegetation) features. Richness, total abundance, and White-footed Mouse and Red-backed Vole abundances were negatively associated with landscape-level habitat fragmentation as measured by patch size and amount of edge. However, patterns were diverse, and even seemingly inconsistent; for example, we often found a positive response to fragmentation at 1 scale but a negative response at another scale. Richness and abundance did not differ significantly among the 3 habitat types. Similar to our study, Bayne and Hobson (1998) did not find a difference in smallmammal abundance between edges and forest interior in Saskatchewan. In contrast, Osbourne et al. (2005) found greater diversity and abundance of small mammals on edges compared to interior-forest sites in West Virginia. Unlike our study, they found additional, open-habitat species such as Microtus pennsylvanicus (Ord) (Meadow Vole ) at edge sites, resulting in greater small-mammal diversity and abundance. Although we found greater small-mammal abundance in larger patches, we did not find an area effect for small-mammal richness. In a study of forest fragments embedded in a matrix of agricultural land in west-central Indiana, Nupp and Swihart (2000) found that species richness increased as a function of patch size and was highest in continuous forest sites. Whereas the range of patches selected by Nupp and Swihart was 0.1–150 ha, our sites were all embedded within patches averaging 96 ± 21 ha (range = 6–380 ha), perhaps too large to detect a species-area relationship for small-mammal species. Our results for individual species correspond well to those reported by previous researchers. In a mixed boreal forest in Saskatchewan, Deer Mice were more abundant in farm–woodlot–edge habitat compared to interior forest (Bayne and Hobson 1998). Similarly, Diffendorfer et al. (1995) recorded that Deer Mice reached highest densities in landscapes with small patches of habitat in old fields in Kansas. Northeastern Naturalist Vol. 22, No. 2 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 295 Although this species was not significantly more abundant at developed-edge sites in our study, we found their abundance tended to be greater in landscapes with more developed edge within 500 m, primarily in the form of pasture habitat. The White-footed Mouse is commonly considered a habitat generalist (Bellows et al. 2001) that uses both edges (Nupp and Swihart 2000) and forest interior (Wolf and Baltzi 2002, 2004). Nupp and Swihart (2000) found that White-footed Mouse did not respond to patch size, and Anderson et al. (2003) found that patches with a greater proportion of edge habitat and more complex understory vegetation (typically smaller patches) had higher White-footed Mouse densities. Wolf and Batzli (2004) did not find significant differences in food availability between interior and edge sites and between prairie and agricultural edges to explain patterns of White-footed Mouse habitat use in east-central Illinois. They suggested that forest edges, particularly natural prairie edges, might be lower-quality habitat compared to interior sites due to higher risks of predation. In our study, White-footed Mouse abundance did not differ among habitat types, and abundance did not differ based on vegetation measures, indicating that this species is also a habitat generalist in northern Massachusetts. Although White-footed Mouse abundance did not differ based on edge-type category in our study, we found significant differences based on landscape patterns. White-footed Mouse abundance increased with patch size, seemingly counter to findings from other studies. For example, Yahner (1992) found that White-footed Mouse was not negatively affected by the degree of fragmentation in managed Pennsylvania landscapes and actually increased as fragmentation increased. Yahner suggested that small area-requirements for White-footed Mouse reduced the negative impact of fragmentation. In addition, Anderson et al. (2006) reported that White-footed Mouse abundance did not differ based on patch size and amount of forest-edge habitat. We also found that White-footed Mouse abundance was positively related to wetland edge within 200 m, suggesting that although this species may be a habitat generalist at smaller scales (edge category and vegetation level), wetland edges may be an important landscape component for this species in New England. That we found landscape-level responses suggests that the scale at which White-footed Mouse habitat use should be measured requires further study. Our results on White-footed Mouse and Deer Mouse should be regarded with caution, even though the patterns we found for these two species in part corroborate results from other studies. We separated these 2 species morphologically in the field based on tail, foot, ear, and body measurements (Choate 1973, Lindquist et al. 2003); however, we did not collect saliva or tissue samples to positively identify each individual through molecular analysis, and differentiating species in the field has not been reliable (Lindquist et al. 2003, Rich et al. 1996). Given the similarity in morphology and the regional overlap in habitat of these 2 species in New England (Parren and Capen 1985), we also analyzed the combined Peromyscus species. This combined variable for adults was not associated with any landscape metric, but was associated positively with conifer basal area (Table 3). In contrast, abundance of Peromyscus juveniles responded to both vegetation and landscape metrics. Northeastern Naturalist 296 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 Vol. 22, No. 2 In our analysis of Red-backed Voles, we found that abundance was associated with both vegetation and landscape metrics (e.g., positively related to patch size). In contrast to our findings, Yahner (1992) found no difference in abundance of Redbacked Voles in landscapes with differing levels of fragmentation. Yahner noted that Red-backed Voles might prefer fragmented landscapes where the presence of specific microhabitats preferred by this species might be more likely. Similarly, Bayne and Hobson (1998) did not find an effect of patch size or a difference between edge and interior habitats on abundance of Red-backed Vole. Furthermore, Fuller et al. (2004) reported that while fragmentation through forest harvesting did not reduce habitat quality for Red-backed Vole in central Maine, several vegetation measures relating to a humid microclimate impacted Red-backed Vole abundance. In our study, natural-edge sites associated with wetlands supported an average of 5 times more Red-backed Vole individuals than drier habitats, and although not significant, this pattern corresponds to the humid microclimate noted by Fuller et al (2004). We also found that Red-backed Voles responded to vegetation differences. The positive relationship that we found between abundance of Red-backed Voles with lower deciduous density but greater conifer basal area may relate to the habitat preference for moist microenvironments with a low density of overstory trees reported by Yahner (1992) and composition of humid mixed forest by Fuller et al. (2004). Our findings that Eastern Chipmunk abundance increased in smaller patches and with lower overstory-tree richness are not surprising. This species is commonly found in residential habitat (Ryan and Larson 1976, Schulze et al. 2005). In addition, Mahan and Yahner (1998) reported that Eastern Chipmunk did not respond to fragmentation differences in a managed forest in Pennsylvania. Furthermore, they found physiological differences based on acorn-crop production, indicating a close relationship to a limited number of overstory-tree species. Our findings of landscape-level fragmentation associated with individual species and community measures (e.g., positive relationship between Red-backed Vole and patch size) that are missing in other studies may relate to the degree of connectivity in our study. The landscape in our region had extensive forest cover (48% within 500 m of sites) compared to other studies cited above, perhaps impacting the relative influence of landscape fragmentation on different species. In contrast, work by Yahner (1992) was conducted in a heavily managed forest in Pennsylvania; Nupp and Swihart (2000) studied mammals in an agriculturally dominated landscape in Indiana; and Wolf and Batzli (2002, 2004) focused on prairie landscapes in Illinois. In other words, small-mammal populations were not isolated from one another in our study area. Furthermore, several of these studies (Bayne and Hobson 1998, Nupp and Swihart 2000) were conducted in communities with a single Peromyscus species, perhaps influencing habitat-use patterns. These differences provide interesting contrasts for further study. Although we found considerable differences in vegetation structure and landscape characteristics among habitat categories in this study, together they did not result in significant differences in community-level and population-level measures for small mammals. Two years of field-work is a standard approach for smallNortheastern Naturalist Vol. 22, No. 2 E.S. Lindemann, J. P. Harris, and G.S. Keller 2015 297 mammal studies, but this amount of trapping may not be enough to delineate actual differences among habitats. Additional years of trapping might yield significant differences if any variation exists among years. Alternatively, increasing the number of study sites, although logistically challenging, may have helped to elucidate significant patterns. Future work in this region should include more abrupt developed edges, such as between forest and recent suburban development, compared to the pasture or agricultural edges in this study. We recommend additional research to build on the growing body of literature on multiscale habitat-use by small mammals in eastern North America, particularly with reliable distinction between Peromyscus species through molecular techniques. Acknowledgments We thank the Gordon College Department of Biology for providing the resources for the completion of this project and the Massachusetts Trustees of Reservations for allowing us access to their reserves. Funding for vegetation and GIS analyses was generously provided by the Nuttall Ornithological Club through the Charles Blake Fund.We appreciate manuscript review provided by K. Preedom and anonymous reviewers. Literature Cited Anderson, C.S., A.B. Cady, and D.B. Meikle. 2003. Effects of vegetation structure and edge habitat on the density and distribution of White-footed Mice (Peromyscus leucopus) in small and large forest-patches. Canadian Journal of Zoology 81:897–904. Anderson, C.S., D.B. Meikle, A.B. Cady, and R.L. Schaefer. 2006. Annual variation in habitat use by White-footed Mice, Peromyscus leucopus: The effects of forest-patch size, edge, and surrounding vegetation type. Canadian Field-Naturalist 120:192–198. Bayne, E.M., and K.A. Hobson. 1998. 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