WATERMAN, JM; Univ. of Central Florida, Orlando: Environmental influences on the social system of the Cape ground squirrel, Xerus inauris

Characterizing the ecological constraints that influence the structure of social groups is a major task in the study of sociality. In many species, as environmental conditions become more severe or the habitat becomes saturated, the rising costs of independent breeding may increasingly skew reproduction within a social group. The Cape ground squirrel (Xerus inauris) lives in the arid regions of southern Africa and evidence suggests that the social structure of this species may differ in areas with greater rainfall and more vegetative productivity. I compared the group structure of X. inauris in three different sites: a low rainfall (<80mm/year), a moderate rainfall (220mm/year) and a high rainfall site (460mm/year). Preliminary data analysis suggests that the low and moderate rainfall sites differ in social structure from the high rainfall site. The average number of adult females in a group was larger in the high rainfall site and, contrary to predictions, the number of individuals delaying dispersal from the area was greater than in the lower rainfall areas. Comparison of the social structure of X. inauris across a gradient of precipitation (indicative of productivity) may uncover environmental thresholds that stimulate social changes.