An early morning birth of a proboscis monkey – Nasalis larvatus Wurmb, 1787 – of Sabah / Borneo.

Births of proboscis monkeys have rarely been documented, especially during the daytime. Nasalis larvatus reproduction is polygynous, with groups of males in which one adult male mates with several females. The gestation period averages about 166 days, although some literature cites longer periods of up to approximately 200 days. Births are almost always single.

There are direct field observations of the birth itself: births usually take place at night or in the early hours of the morning, sitting high up on a branch. The mother then consumes the placenta and cleans the newborn. Daytime births have also been documented on rare occasions, with group members staying nearby and watching.