The Vietnam mouse-deer (Tragulus versicolor), also known as the silver-backed chevrotain, is an even-toed ungulate in the family Tragulidae known only from Vietnam. It was first described in 1910 by British zoologist Oldfield Thomas, who procured four specimens from Nha Trang in Annam. Little is known about its distribution and ecology. After 1910, the Vietnam mouse-deer was reported next in 1990 near Dak Rong and Buon Luoi in the Gia Lai Province. With increasing hunting pressure, habitat loss due to deforestation and no more reports of the species in the wild, the mouse-deer was feared to have gone extinct. The IUCN listed the species as Data Deficient in 2008. In 2019, a study confirmed the presence of the Vietnam mouse-deer in dry low-lying forests of southern Vietnam with camera trap evidence. The mouse-deer is characterised by a rough coat with a strange double-tone coloration unseen in other chevrotains; the front part of the body is reddish brown and contrasts strongly with the greyish posterior. It has big reddish brown ears, white and dark reddish brown marks on the throat. Taxonomy The Vietnam mouse-deer was first described by British zoologist Oldfield Thomas in 1910 by the name Tragulus versicolor, who based his description of the species on four adult male specimens from Vietnam. Between 1910 and 2003 this mouse-deer was generally treated as a subspecies of the greater mouse-deer (T. napu), though it more closely resembles the lesser mouse-deer (T. kanchil). In a taxonomic revision in 2004, the Vietnam mouse-deer was identified as an independent species in Tragulus. Status and sightings Information on the distribution and ecology of this mouse-deer is scarce; it is endemic to Vietnam and has been sighted only thrice in the wild. The four specimens obtained by Thomas were from Nha Trang () in Annam on the southern coast of Vietnam; this need not be the original location for the species, as the specimens could have been traded from elsewhere. The mouse-deer was not reported for another 80 years until a Vietnamese–Russian expedition in 1990 procured an adult male specimen from local hunters near Dak Rong and Buon Luoi in the Gia Lai Province. This specimen, initially assumed to be a Java mouse-deer (T. javanicus), was deposited in the Zoological Museum of Moscow University. A reexamination in 2004 identified the specimen as a Vietnam mouse-deer, noting its strange coloration compared to other chevrotains. Follow-up surveys indicated that