Stumptail Macaque Macaca arctoides. Male stumptails form intense sexual freindships. The partners in a sexual freindship may be of he same age, or one may be considerably younger than the other, perhaps even an infant. Female stumptails also form sexual friendships with one another. White Handed Gibbon and Siamang Hylobates lar and Hylobates syndactylus .
Heterosexual incest is prominent in Gibbons.
Siamang mothers and fathers both interact sexually with their offspring of the opposite sex, as do siblings. Adult males sometimes perform copulation like thrusting with daughters, as well as oral and manual stimulation of their genitals. In one case, a Siamang father was observed fondling his daughter's vulva with his fingers while his younger brother licked her clitoris. Young Bonobos Kissing Marine Mammals Bottlenose Dolphins Tursiops truncatus. Young dolphins are sexually precocious, and incestuos copulations have been observed between males a few months old and their mothers.