The lesser slow loris has a head and body length of about 7-8 inches and vestigial tail. Their weight is about 12 ounces. The fur is short, thick and woolly. Head and eyes are round and small ears almost hidden by fur. Fore and hind limbs are about equal in length. Muscles enable effortless hand grasp and rigidly clenched feet. Nocturnal and arboreal, it seldom descends to the ground. Adult males are strongly territorial and will not tolerate another adult male in the family group. Vocalizations include low buzzing hiss or growl when disturbed, a single hi-pitched rising tone for making contact, and a high pure whistle by the female in estrus.During courtship both sexes make contact by whistles. Births usually occur in the open, not in a nest. Newborn infants look like miniature adults: they have a full fur coat, and their eyes open on the day of birth. Because the infants are so well developed at birth, mothers are able to park them on branches while they go off to search for food. Loris mothers maintain vocal comunication with their babies through soft chirps, and infants will emit a series of rapid clicks and squeaks when they are in distress.