Temporal aspects in the development of Belding's ground squirrels' litter-mate preferences

Four experiments were conducted to determine how experience around the time of natal emergence affected the development of litter-mate preferences in juvenile Belding's ground squirrels, Spermophilus beldingiSocial preferences were ascertained by observing six captive groups, each housed in outdoor enclosures beginning at natal emergence, and recording the frequency of dyadic play. Juveniles preferred their litter-mates as play partners on day 1 above-ground, demonstrating that pre-emergent interactions influenced social development. Whether cross-fostered young displayed play-partner preferences based on relatedness and rearing history depended on when young were exchanged with respect to natal emergence, which suggests that social development is especially sensitive to experience shortly before natal emergence. Juveniles do not display litter-mate preferences if they emerge into an environment from which dams have been removed, but in the present study, if juveniles interacted for 1 week before dams were withdrawn from enclosures, then litter-mate preferences were manifested both before and after dams were withdrawn. These results suggest that a foundation for litter-mate preferences is laid before natal emergence, and that preferences are solidified by interactions between litter-mates on their first few days above-ground. Finally, non-litter-mates that interacted with each other shortly after natal emergence were preferred social partners during later encounters compared with non-litter-mates denied the opportunity to interact shortly after emergence. Collectively, the four experiments demonstrate that social experience around the time of natal emergence is crucial to the developmental process that generates litter-mate preferences in S. beldingi1997 The Association for the Study of Animal Behaviour