Grizzled leaf monkey  (Presbytis comata)

Classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (3).

The grizzled leaf monkey is a small, slender Old World monkey. As its name suggests, its coat is grizzled in colour, being a mix of dark hairs with grey or white, with the exact shade varying between populations (4). The hair on its underparts is typically paler (5), while its head is almost black with longer hair framing a broad grey face (4). Due to differences in appearance, it was once thought that the grizzled leaf monkey consisted of two different species: Presbytis comate in western Java and Presbytis fredericae in central Java. However, it is now clear that the species occurs as a chain of intermediate populations across its range, showing a gradual shift in coat colour from grey to black (6).

The grizzled leaf monkey occurs in western and central parts of the Indonesian island of Java (1).

An inhabitant of both primary and secondary forest, the grizzled leaf monkey was once found from sea level up to 2,565 metres, but is now largely restricted to fragments of forest in the mountains (1).

The grizzled leaf monkey is a folivorous primate, its diet consisting primarily of leaves, but it will also consume fruits, flowers and seeds (5). Like other Colobine monkeys, also known as ‘the leaf eaters’, it is able to digest large volumes of leaves by having a large, multi-chambered stomach, and a forestomach that houses lots of bacteria. Together, these features assist in the breakdown of cellulose, one of the primary components of plants and a substance that is largely indigestible to many animals. However, the specially adapted gut of the grizzled leaf monkey enables it to obtain energy and nutrients from a cellulose-rich diet (7).

Like all leaf monkeys, the grizzled leaf monkey is a tree-dwelling species that is active during the day (5). Group sizes have been documented to range between 2 and 23 individuals (8) (9), with the grizzled leaf monkey also sometimes forming groups with other species such as the Javan langur (Trachypithecus auratus) (10). There is usually only one male of mating age per group, with other males dispersing from the group they were born in before adolescence (11). Juvenile and infant males are known to often engage in social play, an activity which females rarely partake in (11).

Habitat loss is the main threat to the grizzled leaf monkey, with the clearance of Indonesian rainforests resulting in less than four percent of the grizzled leaf monkey’s natural habitat remaining (12). This, combined with the continuous threat of hunting, has resulted in a 50 percent drop in grizzled leaf monkey numbers in the last decade (12), and it was estimated in 1996 that less than 2,500 mature individuals remain in their natural habitat (1).

Remaining populations of the grizzled leaf monkey occur in a number of protected areas in western Java, including Ujung Kulon National Park, Halimun National Park and Gede-Pangrango National Park, which will hopefully offer some protection from habitat disturbance and hunting (1). It is also listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that any international trade in this species should be carefully monitored (3).

View information on this species at the UNEP World Conservation Monitoring Centre.

To learn about wildlife conservation in Indonesia see:

• Wildlife Conservation Society:
  http://www.wcsip.org
• Conservation International:
  http://www.conservation.org/explore/asia-pacific/indonesia/pages/overview.aspx