Initial heterosexual behavior of adolescent Rhesus monkeys (Macaca mulatta)

This report described the first heterosexual encounters of twelve 3-year-old rhesus monkeys, six of each sex. The subjects were all laboratory-born and were reared in wire cages for the first 8 months of life, accompanied only by their mothers. After these animals were weaned, each was placed in a cage with another animal of the same age and sex. The pairs formed in this way remained intact until the animals were 2 years old. When heterosexual dyads were formed, some of the subjects attached and bit the animal with which they had been paired, while the members of other pairs established almost immediate rapport as evidenced by mutual grooming and adequate sexual behavior. The initial sexual interactions of most pairs were uncoordinated, but all eventually demonstrated qualitatively species-typical patterns of sexual behavior. Despite their immaturity, two of these pairs succeeded in producing offspring, both of which were healthy.