Scientific Name Trachypithecus obscurus
Conservation Status Near threatened
Another name for the dusky langur is the spectacled langur. This comes from circles of white fur around their eyes. The rest of the upper body is grey, brown or black. They have a paler underside. Around the mouth they also have a white patch. Their palms and soles are hairless. They are coloured black. The tail is non-prehensile meaning it cannot be used for them to hang from the trees.
On their bottom is a hard calloused pad which is suited to them sitting down which they do for large periods of time.
From head to tail an average dusky langur would be 42-61cm (17-24in) long. The tail adds 50-85cm (20-33in) to this length. They use the tail to maintain balance. Males appear to be heavier than females but this is the only difference between the pair. Females weigh 6.5kg (14lb) on average while males weigh 7.4kg (16lb).
It is believed that these monkeys can live for up to 25 years.
Dusky langurs also go by the name dusky leaf monkey. This is due to most of their diet being composed of leaves. Other foods they eat include shoots, seedlings, fruit (especially if unripe) and flowers. They consume up to 2kg of food a day. They are mostly a herbivorous species but in some cases they have accepted insects in captivity.
They have a multi chambered stomach which allows them to digest the hard leaves. Their salivary glands are also enlarged to help break down the cellulose in the leaves. Most of their day is spent resting as they obtain little energy from the food.
Dusky langurs come from Asia. They can be found in Malaysia, Thailand and Myanmar. They can also be found on some offshore islands.
As an arboreal species dusky langurs live in densely forested areas. Some langurs have been sighted encroaching into human settlements. Humans destroying their habitat is one of the reasons that this species has been in decline.
Breeding can occur throughout the year. It appears to be concentrated between January and March in most areas though. To show they are fertile females will display a genital swelling.
After a gestation period of 145 days a single infant would normally be born. On occasion twins can occur though. These babies are bright orange so they can be easily spotted by all members of the troop.
They spend most of their day on the nipple of their mother.
After about a month they begin to go out exploring on their own. This is also when they start to try solid foods. At this point they begin to play as well.
Following 70 days of life they begin to interact with other members of the group. At this time they also begin to groom group members.
At six months of age they will begin the transition from orange to grey.
The age of weaning is unknown. It is difficult for them to wean as they need their mother to chew leaves for them and then their saliva passes the enzymes for digestion of leaves to the infant.
Sexual maturity occurs after 3 to 4 years.
Dusky langurs live in groups of between 5 and 20 individuals. A male will head up a group of 2 females and their offspring. Excess males leave and form bachelor groups. When a group does not have a head one will take it over and kill all of the offspring from the last male.
They make a variety of calls which are quite complex these include snorts, hoots, murmurs and squeaks.
This species is diurnal meaning they are active during the day. They tend to concentrate most of their activity towards the early morning and afternoon. Moving around their territory is done by climbing, leaping and running along the branches on all four hands.
As a highly territorial species langurs will work to remove any intruders from their territory. If making loud noises doesn’t work they are not afraid to us force to remove these intruders.
Potential predators of this species include snakes and large birds of prey though they are unconfirmed. Humans are also a predator of this species.
Other names for the dusky langur include the spectacled langur, dusky leaf monkey and spectacled leaf monkey.
The word langur is derived from the hindu word for long tailed.