All About The Dusky Leaf Monkey (Trachypithecus Obscurus)
The Dusky Leaf Monkey (Trachypithecus Obscurus)
The Dusky Leaf Monkey is also called as the spectacled leaf monkey, or spectacled langur (Trachypithecus Obscurus) is a species of primate in the Cercopithecidae family.
The dusky leaf monkey is found primarily on the Malay Peninsula, including southern Burma and parts of Thailand.
The dusky leaf monkey with its cute and adorable looks is a primate species. They have large white colored circles around their eyes which give an appearance of a spectacle.
This monkey has also white colored patches of fur around its mouth and stomach while the rest of the fur has a gray to brownish color.
The various subspecies are differentiated by the color of their fur. The color of its fur differs along the 7 subspecies. This dusky leaf monkey is very docile and calm in comparison to other monkeys. It is always fun to watch these small creatures move around on high trees and spend their time searching for food, grooming and relaxing.
Head to body length ranges from 42 to 67cm (16.5 to 26.3 inches), and tail length from 50 to 85cm (19.7 to 33.5 inches). There are no significant morphological differences between males and females dusky leaf monkey except that males tend to be slightly bigger and heavier than females. On average, a healthy adult male monkeys weighs 7.5 to 8.3kg (16.5 to 18.3 pounds), whereas a healthy adult female monkeys weigh approximately 6.5kg (14.3 pounds).
Although the adult dusky leaf monkey is typically gray in color, the baby monkey is born with bright yellow or orange fur and have a pink face. Just after about 6 months, the baby’s fur starts to turn gray, and by 10 months, the young monkey has normally darkened to a gray, just a lighter shade than the adult monkey.
The dusky leaf monkey is arboreal, meaning that it spends the majority of its time high up in trees. They can live in a variety of habitats, from riverine and coastal forests to parks in urban areas, provided that there is enough food supply. They live in small groups and prefer to feed on young leaves, although it will also eat flowers and fruits.
The Lifespan and Size of Dusky Leaf Monkey
Head and body length ranges in male dusky leaf monkey is about 42.5 to 67cm (16.7 to 26.3 inches), with a weight of 18.3 pounds (8.3 kg).
Head and body length ranges in female dusky leaf monkey is about 42 to 60 cm (16.5 to 23.5 inches), with a weight of 14.3 pounds (6.5 kg). The species’ long, non-prehensile tail adds another 50 to 85cm (19.7 to 33.5 inches) to their bodies.
There are recorded captive lifespan of 31 years for the silvered langur (Trachypithecus Cristatus), a primate who shares the same genus, Trachypithecus, as the dusky leaf monkey, has led some scientists to assume that a similar captive lifespan is possible for the dusky leaf monkey.
For a captive female dusky leaf monkey, the recorded average lifespan is 15.3 years.
Dusky leaf monkey is arboreal and quadruped, they prefer a home on tall trees in dense forests. These monkeys prefer also different other habitats which include the coastal forests, urban forests, riverine, parks and botanical gardens.
The dusky leaf monkey is only found in Thailand and parts of the Malay Peninsula. Dusky leaf monkey lives in the primary forest (untouched and mature), secondary forest (regenerated), and lowland forest (altitude below 1 km) in addition to the submontane and montane forest approximately 1,828 m.
Their movement consists mostly of walking or running and leaping. Dusky leaf monkey travels 0.95 km every day on average. Their home range has been reported to be as large as 33 hectares.
What Does The Dusky Leaf Monkey Eat?
The diet of dusky leaf monkey consists of young leaves, seedlings, fruits, and shoots. They feed on 87 different species of trees, consuming both leaves and fruit. Usually, a dusky leaf monkey eats up to 2 kg of food every day. (while weighing only 5 to 9 Kg)
These dusky leaf monkeys have a big stomach, which is divided into various sacs. The upper region of this stomach is associated with the fermentation of green leaves with the support of anaerobic cellulose-degrading bacteria.
Apart from the digestion of cellulose, these bacteria also facilitate the detoxing of the leaves. This bacterial digestion support is an added advantage for the dusky leaf monkey, as they can feed on a wider variety of food.
This dusky leaf monkey can be maintained, in captivity, on sweet potato shoots, carrots, cabbage, lettuce, green beans, maize, Kang kong, and soft fruits. The meat was refused, but certain insects were sometimes accepted.
Plant Foods: leaves; grains, seeds, and nuts; fruit; flowers
Primary Diet: herbivore (Folivore )
The Behaviors of Dusky Leaf Monkey
The dusky leaf monkey is diurnal and very active during day time. They prefer staying up in high canopies of tall trees and move around, climbing, running, and leaping on the branches of the trees.
The dusky leaf monkey has defined territories that the males will guard. Calls tell other dusky leaf monkeys where the boundaries are.
The dusky leaf monkey is known to have interactions within their own group. Groups will have a least one male, 2 females and their young with usually 5-20 individuals in a group.
The adult male monkey has 3 main responsibilities, which include predators detection, holding the group together, and patrolling the boundaries of the territories. The young dusky leaf monkey plays in groups near the vicinity of an adult female. Overall, dusky leaf monkeys are quite social animals.
The dusky leaf monkey has a wide range of calls that are considered to be quite intricate. A variety of snorts, squeaks, hoots, and murmurs are used to communicate with other members of their social group.
The dusky leaf monkey indulges each other with a social play which involves chasing, wrestling, jumping over and pulling one another’s tails.
These dusky leaf monkeys are likely to be important predators of foliage. They might help to disperse seeds. To the extent that they serve as prey for other species, these monkeys may affect local food webs.
As the monkeys dwell upon higher canopies of trees in the forest, they do not have lots of predators. But still can be hunted by raptors, snakes and big carnivorous animals who are able to reach them.
When Does The Dusky Leaf Monkey Sexually Mature and Reproduction?
There is no info available regarding the breeding system of dusky leaf monkeys. But the social system usually involves groups with only one or 2 males.
Reproduction in dusky leaf monkeys is intermittent and not always seasonal. Childbirth usually occurs during the months of January, February, and March, but have been recorded to occur during the summer months also.
Litter size is usually one, although twins are born sometimes. One observational study of a single captive male dusky leaf monkey characterized the mother-infant relationship during the first year of life.
Females monkey have a menstrual cycle lasting approximately 3 weeks. Oestrus is often accompanied by a swelling of the genitalia. Mothers are the primary caretakers to their offspring, who spend the first 20 days of life at their mom’s bosom, attached to her nipple.
Besides nursing, moms exhibit additional maternal behaviors such as scratching, leg pulling, grasping, kissing, and grooming.
Research on the parental behavior of dusky leaf monkeys is lacking. However, we might assume that they are like other primates in that the mother gives the bulk of the parental care. She grooms, feeds, and protects the newborn. The role of the father in parental care is unknowns.
- Sexual mature is reached between 3 and 4 years of age.
- The normal interbirth interval is about 2 years.
- Breeding interval: These monkeys reproduce every two years.
- Breeding season: These monkeys breed intermittently throughout the year.
- Age of Weaning: 365 days
- Average Litter Size: 1-2
- Gestation period: 145 days.
- Range age at sexual or reproductive maturity (Male and Female): 3 to 4 years.
- Average birth mass: 300g.