Nasalis larvatus is also known as Long-nosed Monkey is a reddish-brown arboreal Old World monkey.
The distinctive feature of this monkey is their protruding nose. It’s not defined about the purpose of the large nose, but it has been determined as the result of sexual selection. The female Proboscis Monkey prefers big-nosed male, thus propagating the trait.
This monkey is named after its large, fleshy nose. Both male as well as the females have large noses sometimes they have to push it out of the way before putting something in their mouth. Their nose puff up and turns red when they are excited. They also make noisy honking sounds as a warning when they sense danger.
They have reddish-brown fur on their back and shoulders, which ends at midsection.. Their arms and legs have long, gray gloves and stockings. Their shoulders are covered with Orange fur and head is covered with a cap of darker red fur. Their face is flesh colored with tiny brown eyes. Ears are small and flat which is near their heads.
Males Proboscis is much larger, reaching 72 cm in length, with their tails up to 75 cm, and weight is up to 24 kg.Females are up to 60 cm long, with the weight of up to 12 kg.
This has a large belly, as a result of its diet. Digestive system of this monkey is divided into several parts, this digestive process releases a lot of gas, resulting in the monkey's "bloated" bellies. These monkeys belong to the Asian langurs and they are the only member of the Nasalis genus.
They mainly eat leaves which gives them a place where they are the only medium sized mammal living in the canopy of the forest.
They give birth to one baby at a time. Their gestation period is of 166 days. They will give birth at night times. Females will look after each other infants. They use to stay close to their mother for nearly one year. Male will reach their sexual maturity within 4-5 years and females in 4 years. Their life span is about 20 years.