The development of littermate preferences in juvenile Belding's ground squirrels

Abstract

Abstract. Kin favouritism has been documented widely in free-living ground squirrels (genus Spermophilus), but the development of kin favouritism has not been explained. To investigate the development of littermate preferences in captive Belding's ground squirrels, S. beldingi, groups composed of four dams and 16 juveniles (young-of-the-year) were observed in outdoor enclosures for a period of 5-11 days, beginning when juveniles first emerged aboveground from natal burrows (buried nestboxes). Social play was the most frequently observed social interaction. Littermates played together about twice as often as non-littermates on a per pair basis and juveniles were also more likely to share a burrow at night with their littermates than non-littermates. Independently of relatedness, the sex of a pair also affected play-bout frequencies (m-m>m-f>f-f), as did body-weight differences between juveniles. It was concluded that juveniles displayed social preferences for littermates shortly after they emerged from natal burrows, which suggests that interactions between littermates prior to or just after emergence affected the development of social preferences. Dams indirectly affected the development of social preferences: when dams were not placed in enclosures littermate preferences were not observed. The results of this study support the hypothesis that kin favouritism develops from early social interactions involving dams and littermates. However, it remains to be determined whether the preferences manifested by recently emerged juveniles are maintained throughout the summer and whether such preferences provide the foundation for kin favouritism in adults.