I often saw longtail macaques in Borneo. Medium sized to small, these playful primates live in family groups. One night froma boat on the river we watched a family with many youngsters playing in the trees. This page shows an adult that is about to lean down and get some fruit on a branch above the water, and a mother and baby. The mother is about to climb up and is scoping the path, while the baby clings to her. I saw this species interact with orangutans at the sanctuary, sit near proboscis monkeys without incident, and play with one another with pretty clear joy. I would guess we ran across them at least a dozen times in 10 days, if not more.