Old World monkeys (Superfamily - Cercopithecidae) are primates native to Asia and Africa, inhabiting forests, grasslands, and mountainous regions. One of the two subfamilies is Colobinae; the Langur group forms a part of this family and is commonly called the 'leaf monkey group'. The name is probably derived from the fact that more than 50% of their diet consists of leaves.
The leaf monkey group comprises three generations
Langur (leaf monkey) Group
- Genus Trachypithecus (lutungs)
- Genus Presbytis (surilis)
- Genus Semnopithecus (gray langurs)
Lutungs are Old World monkeys found in Southeast Asia, the southern parts of India, and Sri Lanka.
They are characterized by a long tail and a slim body, along with striking details around their eyes.
The capped leaf monkey or capped langur (Trachypithecus pileatus) lives in the tropical to subtropical dry forests of China, Bangladesh, Nepal, Bhutan, Myanmar, and India.
They're also called ebony lutung or Javan leaf monkey. Javan lutung (Trachypithecus auratus) is indigenous to the island of Java and the islands surrounding Indonesia.
The most common fur color depicted by Javan leaf monkeys is brownish black; the color does not change with age.
Javan lutungs have large salivary glands which help them break down food easily.
Silver leaf monkey or silvery langur / silvery lutung (Trachypithecus cristatus) inhabits the forests of Malaysia, Borneo, and Sumatra.
The silver langur derives its name from silvery-tipped fur that uniformly covers its entire body.
The intestine of a silver leaf monkey is larger than other primates, with the presence of pouches for the purpose of digesting plant matter.
These monkeys prefer a coastal habitat and usually avoid straying from rivers and swamps.
Compared to other monkeys, the silver leaf monkey diet comprises a major portion of mature leaves.
With several subspecies to this type, Dusky leaf monkeys (Trachypithecus obscurus) generally live in the primary forests of Burma, Thailand, and Malaysia.
The fur color varies from shades of gray to brown, with white-colored patches around its eyes and mouth.
The Purple-faced langur (Trachypithecus vetulus) resides in the 'wet zone' (southwest parts) of Sri Lanka.
With a sharp decline in its population since the year 1980, this species makes the list of one of the most endangered primates globally.
François' leaf monkey (Trachypithecus francoisi) is also known as the Tonkin leaf monkey, White side-burned black langur, or François' langur.
The species have a two-chambered stomach; the upper chamber contains bacteria that help in breaking down fibrous foods, whereas the lower chamber has acids that help in digesting other food sources.
The most preferred habitat of the François' leaf monkey is limestone terrain, especially karst topography.
Another well-known leaf monkey is the Gee's golden langur (Trachypithecus geei), that lives in the eastern part of India and Bhutan.
The most striking feature of this primate is its bright golden hair, black face, and long tail.
Considered sacred by Indians, this species of monkey is presently in the endangered list of the IUCN.
The Old World monkeys belonging to this genus are found in areas south of Myanmar and Thailand, including the Malaysian peninsula, and Singapore.
Compared to other langurs, surilis possess underdeveloped brow ridges and have a characteristic nasal bone.
The taxonomy of the Presbytis genus is disputed and several changes have been suggested by scientists.
Little is known about this genus, where ongoing research reveals that the species that belong to it are considered endangered by the IUCN.
These Old World monkeys called Gray Langurs or Hanuman Langurs, are commonly found in South Asia.
They are distributed from the Himalayas to Sri Lanka, and from Pakistan to Bangladesh, spanning most of South Asia.
Gray langurs are characterized by their gray fur, black face, and ears - hence the name.
The taxonomy of the subspecies of gray langurs has been cited differently by varied sources, hence the exact number of subspecies is uncertain as of today.
They are arboreal and terrestrial in nature, living most of their lives on land, and occasionally on trees.
Gray langurs adapt remarkably well to different habitats, and can live in tropical rainforests, mountainous regions, deserts, and even in and around human settlements.
Leaf monkeys, although a fairly broad term, have certain features that make them stand out from the rest of the primates. The main reason for their current endangered state, is urbanization. Needless to say, the reduction of deforestation and promotion of afforestation, is the only way to save this species from getting extinct.