Why do male Cape ground squirrels live in groups?

Abstract

The Cape ground squirrel,Xerus inauris, is a social species of ground squirrel inhabiting the arid areas of southern Africa. The high degree of sociality in this species is due to the occurrence of all-male social groups. This study used scan and all-occurrence sampling to investigate male grouping in this species. Several hypotheses concerning the cause and function of all-male groups were addressed: aggregations around oestrous females, assessment of competitors, enhanced thermoregulation, reproductive alliances, satellite males, information exchange and enhanced predator avoidance. Males were able to detect the onset of oestrus in females. Although oestrus influenced male group size, males continued to group beyond the breeding period. These groups persisted throughout the year, regardless of ambient temperature. Older males were better at finding oestrous females than younger males, but younger males did not preferentially associate with older males to follow them to females. Results best support the hypothesis that males benefit from enhanced predator detection and deterrence. Aggregations of males roaming between groups of asynchronously breeding females may persist beyond the breeding period because the benefits to survival outweigh the relatively minor costs of reproductive competition.