Infant development and weaning in Macaca silenus in the natural habitats of the Western Ghats, India

Abstract

This article reports the development of behaviour in 31 lion-tailed macaque infants from birth to the age of 15 months. The study was conducted during January 2002-June 2005. The study animals included a large group of lion-tailed macaques inhabiting a rainforest fragment in the Western Ghats, India. Two critical stages were observed during the development of the infants: one at the age of five and a half months, and another at the age of nine months. When the infants were five and a half months old, there was a sudden increase in the occurrence of nipple contact, a sharp decline in the per cent of infants making nipple contact after this age, a peak in the occurrence of retrieve by the mother, a peak in the occurrence of play by the infant, and a peak in the occurrence of environmental exploration by the infant, and stabilization of exploration after this age. Up to the age of nine months, the occurrence of an infant approaching the mother and mother punishing the infant continued to increase, and these two behaviours abruptly ended at the age of nine months. Mother grooming the infant occurred with a peak at the infant's age of nine months. It appears that in lion-tailed macaques, the mother actively initiated weaning. It began at the infant's age of five and a half months and was completed by the time the infant was nine months old. The mother, however, increased the frequency of grooming the infant, and thus continued to care for the infant in ways that cost her less in terms of parental investment. A longer duration of nipple contact by some male infants, more retrieval and grooming of male infants, and more proximity of male infants to mothers indicated higher maternal parental investment on male infants.