They form small social groups, containing adults of both sexes as well as young animals. Typically, the adults hunt separately during the night, and the groups gather during the day to sleep. Lorises also groom each other, and play at wrestling. They may spend several hours at a time together, engaging in such social activities.
Female slender lorises are dominant. This is unusual for prosimians, and surprised researchers.
These animals mate while hanging upside down from branches. Lorises in captivity will not breed if no suitable branch is available. One or two young are born at a time.