The social development of an orphaned rhesus infant on Cayo Santiago: Male care, foster mother-orphan interaction and peer interaction.

The social development of a free-ranging male rhesus (Macaca mulatta) infant is described qualitatively and quantitatively from birth to orphaning at nearly 11 weeks of age, and then to 30 weeks of age. Initially the orphan was cared for by four males, but was subsequently adopted by his nulliparous sister. Measures of foster mother-orphan interaction were compared with measures of mother-infant interaction for a control sample of 20 mother-infant pais within the same group. Signs of depression, decreases in play, and atypical patterns of interaction with caretakers gradually diminished over a period of two to three months following orphaning. Through adjustments on the part of both the foster mother and the orphan, their patterns of interaction gradually came to resemble those of mothers and infants of the same age.