Intra-troop affiliative relationships of females with newborn infants in wild ring-tailed lemurs (Lemur catta)

To determine how the birth and development of infants influence their mothers' social relationships with other adult troop members, we observed two free-ranging troops of ring-tailed lemurs (Lemur catta) at the Berenty Reserve, Madagascar. The number of acts of affiliative contact that the mothers received from other adult troop members during the first and second months of infant life were significantly higher than those before they gave birth, and the values during the third month were as low as that before giving birth. Two mothers received acts of affiliative contact less frequently after their infants died, compared with the values while the infants were alive. On the other hand, more than 95% of all acts of licking of infants by adult troop members other than their mothers occurred when the infants were in contact with their mothers. These findings suggest that infants per se and mothers per se were not attractive, but rather the mother-infant pair was attractive to other troop members. Acts of infant-licking were observed in almost all mother-mother pairs and mother-non-mother adult female pairs, and in two thirds of mother-adult male pairs. Moreover, the frequency of infant-licking was not affected by female parity, female and male dominance rank, or infant sex. Therefore, acts of infant-licking, which are widespread among troop members, may function to make or maintain stable social relationships.