Male rhesus monkeys (Macaca mulatta) 3 years of age were studied before, during, and after a series of four separations from equal-aged peers with whom they had formed stable social bonds. The two-week separations were associated with increases in locomotion and environmental exploration and decreases in passivity. There was no suggestion of any "despair" stage as has been reported in younger organisms, thereby suggesting the importance of age as a variable in determining the response to separation.
McKinney WT, Suomi SJ, Harlow HF. Repetitive Peer Separations of Juvenile-Age Rhesus Monkeys. Arch Gen Psychiatry. 1972;27(2):200-203. doi:10.1001/archpsyc.1972.01750260050007