Macaques are a genus of Old World monkeys encompassing over 20 species, including Rhesus, Japanese, and Barbary macaques, inhabiting diverse regions from Asia to North Africa and Europe. These primates are highly social, living in complex, multi-male, multi-female troops. The foundation of their social structure begins during infancy, a time of intense physical and social development. During this period, the infant learns the behaviors and relationships that will shape its adult life within the troop.
Physical Characteristics and Early Life Stages
The macaque gestation period lasts approximately five and a half months, typically resulting in the birth of a single young. Rhesus and cynomolgus macaques, for example, are born weighing between 0.33 and 0.55 kilograms. Newborns are well-developed, with open eyes and fully furred bodies, allowing them to cling to their mother immediately.
A physical marker of infancy is the change in pelage color, as rhesus macaques are often born darker and lighten as they mature. Infants begin suckling within an hour of birth, and mothers introduce solid food, like pieces of fruit or leaves, as early as two weeks. The young gain the ability to move and explore independently around six weeks of age, though they remain closely supervised. Nutritional weaning is a gradual process that begins around four months and is fully completed between 12 and 14 months in the wild.
The Role of the Mother and Social Development
The mother-infant bond forms the central relationship in the life of a young macaque and dictates its early social standing. An infant’s rank within the troop’s strict, matrilineal hierarchy is determined by the status of its mother. Remaining near the mother affords the infant protection and access to resources that reflect her position in the group.
As the infant grows, it interacts with other troop members under the watchful eye of its mother, who restrains or retrieves it if interactions become too intense. Other females may engage in alloparenting, or “aunting” behavior, where they temporarily carry or groom the infant. Through observation and these early interactions, the young macaque learns the complex system of communication and submission gestures, such as teeth-chattering, necessary to navigate the troop’s social rules and avoid conflict with dominant individuals. This period also includes extensive play behavior, which is a practice ground where juveniles develop the social skills and conflict resolution strategies required for adulthood.
The Science of Infant Attachment: Lessons from Macaques
Research involving infant macaques provided insights into mammalian attachment that challenged prior psychological theories. Before the 1950s, the prevailing view suggested that an infant’s bond with its mother was primarily a conditioned response to food provision. Psychologist Harry Harlow’s experiments with rhesus infants demonstrated this was incorrect, fundamentally shifting the understanding of early development.
Harlow presented infant macaques with two inanimate surrogate mothers: one made of wire that held a feeding bottle, and another covered in soft terry cloth that provided no food. The infants overwhelmingly preferred to spend most of their time clinging to the soft, cloth-covered surrogate, only moving to the wire mother for the minimal time required to feed. This established the concept of “contact comfort,” showing that the need for warmth, physical touch, and emotional security is a stronger drive than the need for sustenance. Infants used the cloth mother as a secure base from which they could explore a new environment, underscoring the necessity of a comforting presence for healthy psychological development.