Java mouse-deer

The Java mouse-deer (Tragulus javanicus) is a species of even-toed ungulate in the family Tragulidae. When it reaches maturity it is about the size of a rabbit, making it the smallest living ungulate. It is found in forests in Java and perhaps Bali, although sightings there have not been verified.

This mouse-deer is depicted in Indonesian folklore as Sang Kancil.

The Java mouse-deer has many common names, including Javan chevrotain, Javan mousdeer, or Java Mouse Deer.

The Java mouse-deer's current scientific name is Tragulus javanicus, although other names for it exist, including Tragulus javanica (fem.), Cervus javanicus (basionym), and Tragulus fuscatus (heterotypic synonym).

The taxonomic history of the Java mouse-deer is convoluted; previously, the Java mouse-deer (Tragulus javanicus) was commonly thought to encompass a group of small-bodied chevrotains, but after revisions it was found that this species name should only apply to mouse-deer specimens from Java.

Recent craniometric analyses have begun to shed light on the taxonomic discrepancies. Three species groups of Tragulus have been identified based on craniometric skull analyses and coat coloration patterns. These three species groups are Tragulus javanicus, Tragulus napu, and Tragulus versicolor. Based upon these craniometric analyses, Tragulus javanicus was then further separated based on the organisms' known geographic locations: Tragulus williamsoni (found in northern Thailand and possibly southern China), Tragulus kanchil (found in Borneo, Sumatra, the Thai–Malay Peninsula, islands within the Greater Sunda region, and continental Southeast Asia), and Tragulus javanicus (found in Java). Thus, because of its endemism to the island of Java, the Java mouse-deer is now considered a distinct species, although this fact has not significantly affected its current classification.^{[clarification needed]}

Mouse-deer possess triangular-shaped heads, arched backs, and rounded bodies with elevated rear ends. The thin, short legs which support the mouse-deer are about the diameter of an average pencil.^{[citation needed]} Unlike the antlered true deer, or horned bovids, but akin to Moschus musk deer, male Java mouse-deer have elongated, tusk-like upper canines which protrude downward from the upper jaw along the sides of their mouth. Males use these "tusks" to defend themselves and their mates against rivals. Females can be distinguished from males because they lack these prominent canines, and they are slightly smaller than the males. Java mouse-deer can be further distinguished by their lack of upper incisors, similar to bovids. The coat coloration of the Java mouse-deer is reddish-brown with a white underside, and pale white spots or vertical markings are also present on the animal's neck.

With an average length of 45 cm (18 in) and an average height of 30 cm (12 in), the Java mouse-deer is the smallest extant (living) ungulate or hoofed mammal, as well as the smallest extant even-toed ungulate. The weight of the Java mouse-deer ranges from 1 to 2 kilograms (2.2 to 4.4 lb), with males being heavier than females. It has an average tail length of about 5 cm (2.0 in). Mouse-deer are thought to be the most primitive ruminants based on their behaviour and the fossil record, thus they are the living link between ruminants and non-ruminants.