Dusky Leaf Monkey

Trachypithecus obscurus
Spectacled langur monkey, Spectacled leaf monkey, Dusky langur
The Dusky leaf monkey is a lovely little primate with a unique appearance. The overall coloration of its fur is dark gray, though brownish fur may occur in certain subspecies. The animal exhibits large, white colored patches, surrounding its eyes and looking like sporting eyeglasses. Additionally, the monkey has a white colored circle around its mouth. This color pattern is supplemented by a light head crown and a creamy white stomach patch. The Dusky leaf monkeys are known to live up to 25 years in captivity. There is no information on the life expectancy of this species in the wild, although it's believed to be less than that of captive individuals.
Unknown

population size

25 yrs

Life span

5-9 kg

Weight

42-61 cm

Length

Disrtibution

Dusky leaf monkeys are distributed across the Malay Peninsula, where they are known to occur in southern Myanmar and some parts of Thailand. The natural range of these primates also includes the islands of Langkawi, Penang, and Perhentian Besar. They are arboreal animals. Within their range, Dusky leaf monkeys can be found in various habitats, generally preferring dense forests with an abundance of tall trees.

Habits and lifestyle

Dusky leaf monkeys are social animals, travelling in groups of 5 - 20 individuals, typically consisting of one or more mature males as well as two or more mature females. Mature males of these groups spend their time keeping watch for potential predators, holding the group united and patrolling the home range of the community. As diurnal animals, these monkeys are active during the daytime hours. During most of their active, the primates remain in the tree canopy, at heights of over 35 meters. When travelling between trees, they climb, leap and walk along tree branches, using all of their four legs. With the arrival of the night, dusky leaf monkeys move to their roosts, located in the trees. The communication system of dusky leaf monkeys includes a complex system of vocalizations. The most commonly used calls are snorts, hoots, murmurs and squeaks, through which group members associate with each other.

group name

troop, barrel, cartload, tribe, wilderness

Diet and nutrition

Dusky leaf monkeys are herbivores (folivores), they generally feed upon young leaves, fruits, shoots and seedlings. Those in captivity supplement this diet by sweet potato shoots, lettuce, cabbage, kangkong, green beans, maize, carrots, soft fruits as well as occasional insects.

Mating habits

Dusky leaf monkeys have a polygynous mating system. Males compete for their mating rights. As a general rule, the largest, strongest and most aggressive male will breed with the females. Breeding occurs periodically during the year. Gestation period is about 145 days, yielding a single young. Females produce offspring at intervals of 2 years, typically in January-March, although some may give birth in the summer months. During the first 20 days after birth, the infant is almost constantly with its mother. At around 1 year old, the baby begins climbing, venturing away from its mother and taking solid food. Individuals of both sexes reach sexual maturity at 3 - 4 years old.

Mating behavior

Reproduction season

Year-round

Pregnancy duration

145 days

Independent age

1 year
female

female name

male

male name

infant

baby name

1 infant

baby carrying

Population

Population Trend

Population status

ne
dd
lc
nt
vu
en
cr
ew
ex

Population threats

Dusky leaf monkeys are currently hunted for their meat throughout their range. These animals also suffer from loss and degradation of their natural range because of urbanization, agriculture as well expansion of oil palm plantations. Additionally, population in Peninsular Malaysia is threatened by a high level of road-kill.

Population number

The IUCN Red List and other sources don’t provide the number of the Dusky leaf monkeys’ total population. This species’ numbers today are decreasing today, and the animals are classified as Near Threatened (NT) on the IUCN Red List.

Ecological niche

Dusky leaf monkeys benefit the local ecosystem by their leaf-based diet, due to which these primates act as key seed dispersers of their range. Furthermore, they are, in turn, an important prey species for many predators of the area.

Fun facts for kids

  1. Dusky leaf monkeys forage by pulling down tree branches and holding them to browse on leaves. However, they more often collect leaves, shoots and other type of food by hand.
  2. The four-chambered stomach of this primate has a special structure, similar to that of a cow or antelope, allowing the dusky leaf monkey to digest cellulose of plant cell walls.
  3. Overall, dusky leaf monkey has 7 subspecies, found throughout Malaysia, Myanmar and Thailand.
  4. The structure of their hands and feet animals is very similar to that of humans. Dusky leaf monkeys exhibit well-developed fingers and opposable thumbs.
  5. Dusky leaf monkeys are born with a very colorful coat, typically orange or bright yellow. During the first 6 months of their lives, this vivid color pattern gradually turns to grey.
  6. This species is otherwise called the 'Spectacled langur'. The word 'langur' has a Hindu origin and means 'long-tailed'.
  7. Typical social behaviors of dusky leaf monkeys include plays such as chasing, jumping or wrestling.
  8. These primates are known for their good appetites: each individual eats about 2 kg of food per day, while weighing 5 - 9 kg on average.