WHY DO MALE CAPE GROUND-SQUIRRELS LIVE IN GROUPS

The Cape ground squirrel, Xerus inauris, is a social species of ground squirrel inhabiting the arid areas of southern Africa. The high degre e of sociality in this species is due to the occurrence of all-male so cial groups. This study used scan and all-occurrence sampling to inves tigate male grouping in this species. Several hypotheses concerning th e cause and function of all-male groups were addressed: aggregations a round oestrous females, assessment of competitors, enhanced thermoregu lation, reproductive alliances, satellite males, information exchange and enhanced predator avoidance. Males were able to detect the onset o f oestrus in females. Although oestrus influenced male group size, mal es continued to group beyond the breeding period. These groups persist ed throughout the year, regardless of ambient temperature. Older males were better at finding oestrous females than younger males, but young er males did not preferentially associate with older males to follow t hem to females. Results best support the hypothesis that males benefit from enhanced predator detection and deterrence. Aggregations of male s roaming between groups of asynchronously breeding females may persis t beyond the breeding period because the benefits to survival outweigh the relatively minor costs of reproductive competition. (C) 1997 The Association for the Study of Animal Behaviour.