Gray Langur
Sri Lanka Common or Grey Langur
(Presbytis entellus thersites)

The gray langur, with the midnight-black face and the macaque, or the red monkey are seen widespread in Sri Lanka's jungle areas and sometimes even in the small villages.The larger of the two species, the langur, lives in large groups among the trees and is usually not aggressive. Groups of these monkeys are a common sight at some of the Buddhist temples in the dry region, and most often seen begging for give-aways, or if un-successful, stealing, from the unsuspecting visitor.

The red monkey, with a brown colored coat and a pink face, is far more aggressive, and quick tempered. This species, if provoked, have known to attack humans occasionally. There are several other species of monkey in the Sri Lanka jungles, but theyare confined to the hilly and mostly inaccessible areas and for this reason are not seen by the average visitor to the island.

Sinhala: vandhura The Sri Lanka common or grey langur (usually referred to as the grey langur) inhabits the jungle areas of the low country dry zone. These monkeys are light grey in colour, with contrasting black faces and hands. They have long tails which sometimes give them away when they are sitting in trees. Grey langurs live in family troops numbering from several to 30 members, and lead by a dominant male. They spend as much time on the ground as in the trees. Their food consists of fruits, leaves, flowers and seeds. The grey langur is also called the Hanuman monkey, a reference to the Indian epic, the Ramayana, in which there is tribe of monkeys lead by a general called Hanuman.

Toque Monkey 
(Macaca sinica sinica) 
Sinhala: rilawa The toque monkey, a species endemic to Sri Lanka, inhabits jungle areas. This species is represented by three races, each differing in colour, the most prominent being a bright reddish-brown. Both sexes have very large cheek pouches. Toque monkeys live in family troops of 20. The two low country races spend much of their time on the ground, while the mountain race is more arboreal. They are mainly diurnal, feeding on fruits, seeds, flowers, insects, and lizards - putting their large cheek pouches to good effect! 

Western Purple-Faced Langur
Semnopithecus vetulus nestor Bennett, 1833 Sri Lanka (2004)
With much of its former range now occupied by Sri Lanka's capital city, the western purple-faced langur is one of the few primates in the world critically threatened by urban development.
Endemic to Sri Lanka, this langur is restricted to a small area of the wet zone in the west of the country, most of which is threatened due to human activities (crops, infrastructure and industry, settlements, deforestation and forest fragmentation, and hunting). Colombo, the capital city of Sri Lanka, is in the center of its very limited range. Hill (1934) indicated that it was common around the capital, but this is no longer the case.
Forest cover in Sri Lanka has declined drastically since the late 1950s, and the area of occupancy of this langur has been reduced to a highly fragmented 1,900 km² (Molur et al., 2003). Although still quite numerous (>10,000), the declines in numbers are expected to have been precipitous — estimated at more 80% in three generations due to urbanization and development. They are highly arboreal and need good canopy cover, and there are possibly less than three forests that can support viable populations, none of which are protected areas set aside for conservation.

The human-modified areas that sustain much of the langur population, such as gardens and rubber plantations, are under private ownership and changing rapidly due to human population expansion and development; large trees are cut down and entire forest patches are destroyed for housing and development. This severely restricts home ranges, isolating the groups, and resulting in escalated conflict with humans and low juvenile recruitment rates (Dela, 1998).

Long-term studies by Dela (1998) have shown that this taxon is unique in having subpopulations adapted to a diet high in mature/ripe fruit, a feature as yet unrecorded for any other colobine, and are dependent on fruits cultivated by humans. Its geographical range has a very high human population density, and home ranges are being compressed due to loss of tree cover. Censuses are urgently needed to identify forest areas for conservation and to better quantify the decline of subpopulations in space and time, and to provide a better understanding of their demographics (especially reproductive rates, population turnover and dispersal) in the extremely disturbed habitats where they survive today.
Jinie Dela and Noel Rowe

References
Dela, J. D. S. 1998. The ecology and social biology of a selected population of the western purple-faced leaf monkey (Trachypithecus vetulus nestor = Presbytis senex nestor). Ph.D. thesis, University of Peradeniya, Peradeniya. Hill, W. C. O. 1934. A monograph on the purple-faced leaf monkeys (Pithecus vetulus). Ceylon Journal of Science (B) 19 (Pt.1): 23-88.
Molur, S., Brandon-Jones, D., Dittus, W., Eudey, A., Kumar, A., Singh, M., Feeroz, M. M., Chalise, M., Priya, P. and Walker, S. (eds.). 2003. Status of South Asian Primates: Conservation Assessment and Management Plan (CAMP) Workshop Report, 2003. Zoo Outreach Organisation, IUCN/SCC Conservation Breeding Specialist Group — South Asia, Coimbatore, India. viii + 432pp.
Suggested citation:

Dela, J. and Rowe, N. 2005. Western Purple-face Langur, Semnopithecus vetulus nestor Bennett, 1833. In: Primates in Peril: The World's 25 Most Endangered Primates 2004-2006, R. A. Mittermeier, C. Valladares-Pádua, A. B. Rylands, A. A. Eudey, T. M. Butynski, J. U. Ganzhorn, R. Kormos, J. M. Aguiar and S. Walker (eds.), p.28-29. Report to IUCN/SSC Primate Specialist Group (PSG), International Primatological Society (IPS) and Conservation International (CI), Washington, DC.