Repeated separations of 2-year-old squirrel monkeys from familiar mother surrogates

Six squirrel monkeys (Saimiri sciureus) during their first year of life were isolated and repeatedly separated from cloth mother surrogates. Subsequently, they were returned to the colony for 1 year and received visual access to normally reared squirrel monkeys. At 2 years of age, the surrogates were reintroduced to the monkeys under conditions identical to those of their first year through cycles of separation and reunion of the surrogate. These monkeys displayed increased high-energy activity, indicative of the classic protest response upon separation, but did not display a depressive phase. Also, during the 2-year test, the monkeys manifested enhanced levels of several self-directed behaviors compared to a group of socially reared control monkeys.