going off the rails on a chevrotain

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I'm back with you today on another episode of "small brown mammal I've never heard of".

Chevrotains are small mammals in the order Artiodactyla and the family Tragulidae, and are also called mouse deer. They are the smallest hooved animals that exist. Kind of funny that there are also deer mice, which are a group of mice species.

Mouse deer are restricted to Africa and Asia tropical forests, with the smallest species being about rabbit sized. There are 10 species and seem to be unchanged by evolution over millions of years. They are somewhere between pigs and deer on the evolutionary tree. Mouse deer are not true deer, as they are not in the family Cervidae. Unlike deer, they don't hang out in herds and are instead solitary.

The name chevrotain comes from the French word chevrot (kid or fawn), and means "little goat".

They are considered ruminants, meaning they are herbivores with foregut fermentation (like cows), so they have four-chambered stomachs. But they are 'primitive' ruminants, like a link between the living ruminants and non-ruminants today. They are brownish in color, with males smaller than females, and are nocturnal, with one species being especially associated with water. Mouse deer eat vegetation and a lot of fruits, actually a lot of fruit for an ungulate. Because they're so small, mouse deer apparently can't efficiently digest high fibre diet items. Fruits are low fibre and highly digestible.

Mouse deer prefer highly dense environments with a lot of thick cover, and avoid open areas, presumably to avoid predation. The presence of rock boulders and snags also seem important for some species to hide in. This also makes them really hard to study, which is why a lot of research relies on camera traps and dung presence.

The mouse deer doesn't have any headgear ornamentation (no antlers etc) but they are similar to Chinese water deer in having long upper canines and some sharpish premolar teeth. The male's canines are really long but the female has stunted ones. 

They really only interact with each other during the mating season. Mouse deer do mark their territories with droppings and some scentmarks. They have a chin gland that some species use to mark a mate or rival's back during either mating or aggressive encounters. When they coming together in mating season, the largest and oldest individuals tend to be dominant, but they also don't seem to establish really clear hierarchies either.

The sharp teeth are for males fighting each other during mating periods, but fights are brief.

A rare Vietnamese chevrotain:

One species, the silver-backed chevrotain, is considered to be one of the least studied ungulates. It lives in Vietnam. It was first described by western science in 1906 and then not officially recorded again until 1990 (!). Then it went through a second period of non-detection until it was finally sighted via camera traps in 2017. It couldn't be listed as threatened or endangered at the time because so little was known about it.

Research published in 2026 indicated at least five existing populations in Vietnam, indicating the species to have one of the smallest known ranges of any ungulate.

Unfortunately all of its populations are centered around regions of known "snaring crises", areas where local hunters use snares to kill wildlife. Results from this study allowed listing of the species as critically endangered on Vietnam's list of species, although the international list (IUCN) still doesn't have enough information.

In culture:

The mouse deer is featured in Malay folklore, where it plays a trickster kind of role and is named Sang Kancil. In these stories, Sang Kancil always gets the upper hand against other, larger animals like crocodiles and tigers. There is a Malay idiom that says "Cerdik macam Kancil", meaning "clever like a mouse-deer". The character is kind of like Coyote from Navajo tales or Br'er Rabbit from the US south.

This article from BiblioAsia and written by Theresa Fuller has great coverage of Sang Kancil tales. Theresa has also written and published a collection of these stories - Eating the Liver of the Earth: Mousedeer Tales.

Netflix Malaysia has an animated series about Sang Kancil (it's in a very Paw Patrol-style), with a full-length movie released in 2024. Several episodes of the series are on Youtube, although it's in the Malay language.