Temporal overlap of female kin in Columbian ground squirrels (Spermophilus columbianus)

Summary Columbian ground squirrels (Spermophilus columbianus) were live-trapped from 5 to 7 years at three sites in southwestern Alberta, Canada. The two most common adult matrilineal relatives for 2-year-old females were the mother and a 1 year older non-littermate sister. Co-occurrence of female kin depended firstly on size and sexual composition of litters and secondly on age-specific survival and recruitment rates. Adult matrilineal kin frequently coexisted among breeding females of this species, leading us to predict a social system strorgly influenced by nepotism. However, the life history traits of S. columbianus suggest an adult female kin cluster unlike that found for other species of Spermophilus in which littermate sisters are common. If availability of adult female kin influences kin-differential behaviour, then female S. columbianus should favour mothers, daughters and non-ittermate sisters.