Home range perturbations in Tamias striatus : Food supply as a determinant of home range and density.

A 12-week experimental study on the responses of home range size and population density of eastern chipmunks, Tamias striatus, to perturbations in food resources was conducted at the Pymatuning Laboratory of Ecology in Pennsylvania. The study involved a total of 97 animals and 1,036 captures. Home ranges were determined for all animals marked and captured four or more times. Mean home ranges were calculated for three different experimental periods; a before-seeding period, a seeding period, during which an essentially unlimited supply of a preferred food (sunflower seeds) was available, and a post-seeding period when all seeds were withdrawn. Home ranges during the seeding period contracted in response to the food source supplied in seed trays distributed throughout the plot. The differences between the before and during mean home ranges was significant (P<0.05). Home ranges subsequently expanded after removal of the seeds. The population density also increased over 50% during the seeding period, both in response to the abundant food source and the contraction of resident home ranges. The density subsequently declined to its initial level in the post-seeding period. The replacement of home ranges of chipmunks which died during the study by the establishment of new, similar home ranges by immigrants, and the expansion of existing home ranges by residents into the vacated areas was also observed.