AbstractInfant squirrel monkeys of the Colombian and Peruvian varieties were reared on surrogates until they were 24 weeks old. The weights of the Colombian animals were consistently greater than those of the Peruvian animals, and the males of each type were heavier than the respective females. The behavior of both groups was similar in most respects and much like that reported for surrogate‐reared rhesus infants. However, the Colombian infants did spend less time than the Peruvians on the surrogate during the first 12 weeks, and none of the animals exhibited anything resembling the stereotyped body‐rocking that has been described for the surrogate‐reared r