THE ONTOGENY OF SOCIAL PLAY IN A FERAL TROOP OF VERVET MONKEYS (CERCOPITHECUS-AETHIOPS-SABAEUS) - THE FUNCTION OF EARLY PLAY

We describe the ontogeny of social play over the first 30 weeks of age in a troop of feral vervet monkeys (Cercopithecus aethiops sabaeus) i n Barbados. Play time increased rapidly for the first 10 weeks but rem ained relatively constant thereafter. The form of play changed with in fant age; bouts became more frequent but of shorter duration. Play tim e, bout frequency, and bout duration at a given age differed between i nfants; younger infants altered their play patterns to complement thos e of older infants. All infants played more within their own year clas s than with older juveniles; play time increased with decreasing age d ifference between the infant and the play partner. Infants terminated a higher proportion of their play bouts the greater the age difference between themselves and their play partners. Preferred play partners a re therefore individuals of similar age that will be similar in size a nd have matched motivation to play and form of play. Neither play time nor proportion of bouts initiated or terminated was correlated with t he social rank of the play partner, which suggests that play is not di rected toward individuals that may be high-value alliance partners. Ma ternal intervention in play occurred primarily when infants were < 10 weeks old. It was not correlated with the age or social rank of the mo ther or with the age or social rank of her infant's play partner. Infa nts played more and terminated a lower proportion of their play bouts in the absence of their mothers than in their presence. Our results ar e consistent with the hypothesis that the primary function of early pl ay is to enhance physical fitness and to develop coordination and othe r fighting skills, with minimal risk of injury.