An Experimental Analysis of Social Spacing in Tamias Striatus

We report on a series of experiments performed on a population of free—living eastern chipmunks, Tamias striatus, inhabiting a forest in northwestern Pennsylvania. The experiments were designed to examine, via pertubations of food supply and/or population density, the relationship between home range size, food availability, and population density. When food levels were increased within an area, a simultaneous effect was noted: mean home range size decreased and population density increased through recruitment from neighboring habitats. Whether the cause of the decreased patterns of movement was the increased food supply or the elevated population density was determined in subsequent experiments. When population density was held constant and food supplies were experimentally increased, there was a significant reduction in mean home range sizes when compared to the normal (control) situation. When food supplies were undistributed, put population density was greatly reduced, there was no change in the mean home range size over that determined at higher mean home range size, whereas population density, at least at the levels we examined experimentally, has no effect on movement patterns. These results are in accord with those theories relating movement patterns to resource abundance, but are not in accord with hypotheses suggesting that the home range sized and population density and inversely associated.