Habitat Associations and Demography of Small Mammals in 4 Forest Cover Types on Quantico Marine Corps Base, Virginia
Williams, Julie Marie
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I examined small mammal demography and habitat associations in 4 forest cover types on Quantico Marine Corps Base, VA. Study sites included clearcut, shelterwood, mature-riparian, and mature-upland habitats. My primary objective was to determine whether the abundance, species composition and demographic characteristics (density, survival, reproductive effort) of small mammals varied with respect to forest cover type. Secondarily, I was interested in identifying patterns of small mammal habitat selection and the factors that influence those patterns at micro- and macroscales. Small mammals were captured from May 1997-January 1999 on 10 sites (2 clearcut, 4 shelterwood, 2 riparian, and 2 mature) using a combination of Sherman live-traps and pitfall traps. Small mammal abundance and demographic characteristics were examined across forest cover types using a combination of statistical analyses, including Chi-square tests, Kruskal-Wallis tests and repeated measures ANOVA. I surveyed microhabitat features at individual trap stations (n=1000) using variable sized plots and the point quarter method and used these data to determine macrohabitat characteristics for sites (n=10). I examined species-habitat relationships at micro- and macro-spatial scales using Kruskal-Wallis tests, Wilcoxon Rank Sum tests, simple linear regression, stepwise multiple regression and stepwise logistic regression. Fourteen species of small mammals were captured over 7 trapping occasions. Five species including white-footed mice (Peromyscus leucopus), northern short-tailed shrews (Blarina brevicauda), eastern chipmunks (Tamias striatus), meadow voles (Microtus pennsylvanicus), and woodland voles (Microtus pinetorum), accounted for approximately 95% of the total number of individuals captured. Overall relative abundance and species composition of small mammals differed significantly across forest cover types. Catch per unit effort was greatest in shelterwoods followed by riparian, clearcut and mature forest cover types. I found significant differences in the abundances of white-footed mice and eastern chipmunks across forest cover types but not in those of northern short-tailed shrews, meadow voles or woodland voles. Shelterwood stands provided the highest quality habitat for white-footed mice and eastern chipmunks while clearcut stands provided high quality habitat for northern short-tailed shrews. Assessments of habitat quality for other species were based on weak evidence or inconclusive. Microhabitat preferences for the 5 small mammal species with > 100 captures were generally consistent with those previously reported in the literature. White-footed mice, eastern chipmunks and northern short-tailed shrews were associated with woody debris and brushy microsites, while meadow voles were associated with grassy vegetation and woodland voles with the presence of soft mast and woody stem densities. For each of these species, microhabitat was able to predict presence at individual trapping stations at a level better than expected by chance. For white-footed mice and woodland voles, however, habitat selection was found to be dependent upon macrohabitat, suggesting that habitat selection for these species is dynamic. Macrohabitat features were related to the abundance of several small mammal species. In general, the habitat characteristics important to individual species at microscales tended to be important at macroscales as well. The results of this study suggest that current even-aged forest management practices on Quantico Marine Corps Base are compatible with the maintenance of native populations of small mammals. Disturbances created by harvesting, at least temporarily, resulted in favorable microhabitat conditions for a variety of small mammal species. Species such as southern flying squirrels, however, were sensitive to disturbance, although it is likely that successional changes allow rapid recolonization of disturbed sites.
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