Maternal encouragement of infant locomotion in pigtail macaques, Macaca nemestrina

This study investigated whether pigtail macaque mothers encourage their infants' independent locomotion by increasing distance from them and displaying a retrieval signal, the pucker face. Fifteen mother-infant pairs living in a large captive social group were focally observed during the first 12 weeks of infant life. Mothers puckered to their infants only when out of contact with them, and the pucker was followed by reduction in distance by the mother or the infant. The pucker was significantly associated with an increase in distance initiated by the mother, and mothers that frequently puckered to their infants were also those that frequently left them. Multiparous mothers puckered to their infants more than primiparous mothers. The infant's initiative in reducing distance after the pucker increased with its age, and the latency of its response gradually decreased in the first 6-7 weeks of life. Infants that received more puckers from their mothers spent less time in contact with them and approached and left them more frequently than infants that received fewer puckers. The evidence is insufficient to assess unequivocally whether developmental changes in infant responses to the pucker reflect social learning or maturation of motor skills. (C) 1996 The Association for the Study of Animal Behaviour.