THE NATURE AND FREQUENCY OF SOCIAL INTERACTIONS AMONG FREE-LIVING PRAIRIE VOLES (MICROTUS-OCHROGASTER)

Hypotheses relating the behavior of voles to their population cycles o ften assume that the rate of social interaction increases with populat ion density. To test this assumption, we examined the frequency of soc ial interactions in a population of prairie voles (Microtus ochrogaste r) over a 7-year period. In addition, we characterized space use by re sident animals, patterns of visitation by nonresidents to nests, and p articipants in social interactions. Social groups within the populatio n typically displayed little overlap in their use of space, even at hi gh population densities. Nevertheless, nonresidents, particularly wand ering males, were captured as visitors at nests. The number of visits per social group did not increase in a simple linear manner with popul ation density and was particularly variable when there were fewer than 100 animals/ha. At such times, more single females and fewer pairs re ceived visits from males than expected based on the frequency of occur rence of these groups in the population; a similar pattern was noted d uring periods of high population density (greater than or equal to 100 animals/ha) but the comparisons failed to reach statistical significa nce. Furthermore, at high population density, more communal groups rec eived visits from females than expected. Patterns of visitation to com munal groups were influenced by the number of adult male residents (wi nter only), but not by the number of adult female residents or presenc e of philopatric female offspring. These data indicate that the freque ncy of social contact in prairie voles does not increase linearly with population density and is influenced by the spacing and possible mate -guarding behavior of resident animals.