Social play and the development of temperament in juvenile Belding’s ground squirrels (Urocitellus beldingi)

We evaluated the hypothesis that social play behavior influences the development of temperament in young animals, using docility as a measure of temperament. We observed the play behavior of juvenile Belding’s ground squirrels (Urocitellus beldingi) during the developmental period in which play primarily occurs, and conducted behavioral tests measuring docility at the beginning and end of the play interval. Tests involved handling squirrels and recording their responses. Body mass was a reliable predictor of docility at the beginning of the play period. Rates of social play and maximum distances traveled from the natal burrow during the play interval were reliable predictors of change in docility across the play period. Juveniles who played at higher rates and traveled farther from the natal burrow tended to have greater decreases in docility over the play interval, supporting the idea that social play and other early-life experiences might influence the development of tendencies toward more active responses in this species. To gauge docility beyond the juvenile period, we conducted docility tests on females who weaned a litter during the study period, and on yearlings for whom play data were available from the previous year. Among females who weaned a litter during the study period, docility decreased significantly between gestation and emergence of young from the natal burrow. However, docility during gestation and lactation were reliable predictors of docility at litter emergence among reproductive females, suggesting that although docility may vary with reproductive state, individual squirrels may have their own distinct tendency toward docility. Rates of juvenile social play were a significant predictor of docility among yearling squirrels, raising the possibility that possible effects of social on the development of docility may be long term.