Indochinese Silvered Langur
(Trachypithecus germaini)
During the 1950s–1990s, populations of Indochinese silvered langur were almost universally considered conspecific with the better-known, widespread and numerous silvered leaf monkey (T. cristatus) of Sundaic Southeast Asia (Malay peninsula, Borneo, Sumatra and associated small islands) [1]. Recent morphological and molecular analyses suggest, however, that these Sundaic and non-Sundaic populations are not conspecific, although this view is not universal [2]. Additionally, some used Indochinese silvered langur for all non-Sundaic populations [3,4], while others separated them into two species [5,6,7,8,9]: Indochinese silvered langur to the west of the Mekong and Annamese silvered langur (T. margarita) east (although this barrier is not yet confirmed) [9].
Orange infant, Kien Luong, Vietnam
Photo by Adam Pérou Hermans
Feeding, Kien Luong, Vietnam
Photo by Andie Ang
Research to date
The Indochinese silvered langur is one of the most neglected primates in terms of field research and conservation. There are only a few sightings documented in Vietnam over the last 50 years, possibly as a result of limited surveys. Consequently, there is currently no population estimate of the silvered langurs in Vietnam, but they are listed as endangered. In Vietnam, they are only recorded from Kien Giang Province, south of the Mekong.
References
[1] Timmins R.J., Steinmetz R., Poulsen M.K., Evans T.D., Duckworth J.W. & Boonratana R., 2013. The Indochinese Silvered Leaf Monkey Trachypithecus germaini (sensu lato) in Lao PDR. Primate Conservation 26: 75-87
[2] Brandon-Jones D., Eudey A.A., Geissmann T., Groves C.P., Melnick D.J., Morales J.C., Shekelle M. & Stewart C.-B., 2004. Asian primate classification. International Journal of Primatology 25: 97-164
[3] Groves C.P., 2001. Primate taxonomy. Smithsonian Institution Press, Washington, D.C.
[4] Groves C.P., 2005. Order Primates. In: Mammal species of the world, 3rd edition, Wilson D.E. & Reeder D.M. (eds.), Johns Hopkins University Press, Baltimore, M.D.: 111-184
[5] Nadler T., Walter L. & Roos C., 2005. Molecular evolution, systematics and distribution of the taxa within the silvered langur species group (Trachypithecus [cristatus]) in Southeast Asia. Zoologische Garten 75: 238-247
[6] Francis C.M., 2008. A field guide to the mammals of Southeast Asia. New Holland, London
[7] Roos C., Nadler T. & Walter L., 2008. Mitochondrial phylogeny, taxonomy and biogeography of the silvered langur species group (Trachypithecus cristatus). Molecular Phylogenetics and Evolution 47: 629-636
[8] Hoang Minh Duc, Covert H.H., Roos C. & Nadler T., 2012. A note on phenotypical and genetic differences of silvered langurs in Indochina (Trachypithecus germaini and T. margarita). Vietnamese Journal of Primatology 2 (issue 1): 47-54
[9] Roos C., Boonratana R., Supriatna J., Fellowes J.R., Rylands A.B. & Mittermeier R.A., 2013. An updated taxonomy of primates in Vietnam, Laos, Cambodia, and China. Vietnamese Journal of Primatology 2 (issue 2): 13-26