Availability of Resources and Use of Space in Eastern Chipmunks, Tamias striatus
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The adaptive significance of the use of resources is a central issue in population ecology. Empirical and theoretical studies have examined the relationship between mean size of home range and environmental variables. Few studies have examined age, gender, and individual variation in these relationships. We examined the relation between patterns of variation in size of home range in eastern chipmunks, Tamias striatus, and distribution and abundance of resources in northwestern Pennsylvania. Previous research on Tamias showed that mean size of home range responded quickly to changes in abundance of resources, suggesting that individual variation in size of home range would be tied to resources. We captured 278 individuals 3,933 times. Forty individuals were studied in 1981 and 49 in 1982. Home ranges were calculated and all mast-producing trees were mapped yielding expected abundance of resources for all home ranges. Abundance of resources was an increasing function of size of home range even when corrected for competition for access to resources, contrary to predictions based upon models of use of space. When examined by age and sex of chipmunks and by different species of mast-producing trees, we noted that the distribution and abundance of white oaks influenced the distribution of age and sex groups of the study area and appeared to be a disputed resource for adults. Studies of patterns of age, sex, and individual variation in complex behaviors are logistically challenging, but they are the best way to empirically test models in population ecology dealing with the adaptive significance of access to space and resources.
