Has bare, blue-skinned buttocks. Both males and females have this, but a male's maturity is openly advertised by the brightness of his red and blue genitals. They are sometimes called Hamlyn's monkey, after the animal dealer who first brought them to the London Zoo. One young, rarely twins. Gestation 5-6 months.
Babies have a yellow-brown coat and pink face.
They make quiet calls. Dense bamboo forests from 900-4,500m. The male's role is more as a lookout than a protector and often accompanies the group from a distance. But Owl-faced males are intensely protective and will rush forward towards a threat while female and young escape. Sometimes, these smaller groups may combine into larger groups and thus contain several males.