Lost to the outside world for a generation—and feared extinct—a small deer-like species with tiny fangs has been photographed tiptoeing through a dry lowland forest in southern Vietnam. The last known scientific recording of the animal, known as the silver-backed chevrotain (Tragulus versicolor), dates to 1990, when a hunter killed one and donated the specimen to scientists.

"It's a really cool species, and we'd long hoped to find proof they were still around," says Andrew Tilker, a biologist specializing in Southeast Asian wildlife at Global Wildlife Conservation, an environmental group, and a doctoral student with the Leibniz Institute for Zoo and Wildlife Research in Germany.

The silver-backed chevrotain, also known as the Vietnamese mouse-deer, is about the size of a large rabbit, with a silver sheen on its rump. The creatures have tusk-like incisors, visible in the new photographs of the animals. Because chevrotains lack horns or antlers, and the fangs are especially long in males, scientists think the males use them to compete for territory and mates.

The researchers behind the discovery, described in a paper published November 11 in Nature Ecology & Evolution, say they hope it will lead to better protection for the species, which is primarily threatened by the use of wire snares. The method the researchers used to find the creature could also help find other "lost" species, they say.

Lost a species? Ask the locals

Tilker and colleagues went to the dry coastal forested areas in the vicinity of the southern beach city of Nha Trang where, in 1910, the only other scientific specimens were collected. Camera traps in Vietnam's wet tropical forests have never recorded a sighting, so it may be that these animals prefer a dry, thorn scrub forest habitat.

"Although such forests are not common, there are parts of Vietnam that remind me of my home state of Texas," Tilker says.

The exact locations of the 1910 sightings weren’t explicitly recorded, so the researchers visited communities in the region to talk to local hunters and forest experts to find out if they'd seen chevrotains with a silver-coloured rump. (There is another species of chevrotain called the lesser mouse-deer that is fairly common but lacks the silver rear end.)

Illegal hunting with wire snares is widespread throughout Vietnam, so these conversations were difficult. The scientists had to spend time getting to know them to gain their trust, says An Nguyen, also with Global Wildlife Conservation, who led the expedition.

"However, people have become very concerned about how much wildlife has vanished in the past five to 10 years," Nguyen says. "They know it's because of overhunting and the use of snares."

Eventually locals took Nguyen and other expedition members to places in the forest where they'd recently seen what looked like the "lost" chevrotain. Camera traps were set up between November 2017 and July 2018. They snagged photos from 280 separate encounters with individual silver-backed chevrotains, although some of these could've been repeat sightings, making it unclear how many live in the area.

"I was overjoyed when we checked the camera traps and saw photographs of a chevrotain with silver flanks," he said.

Besides the silver-backed chevrotain, wire snare poaching has pushed other endemic deer-like species to the brink of extinction, including the saola (Pseudoryx nghetinhensis) and the large-antlered muntjac (Muntiacus vuquangensis).

This illegal hunting, or poaching, is driven by demand for bushmeat in East Asia—and has led to the disappearance of animals in intact habitats in Vietnam. This conundrum is known as "empty forest syndrome" because wire snare traps can indiscriminately catch and kill nearly everything that walks on the forest floor.

Don’t give up

Almost nothing is known about the silver-backed chevrotain, the new study notwithstanding. Based on the photographs and videos, they appear to be solitary, foraging for fruits and plants during the day.

"They walk on the tips of their hooves and very cautiously tiptoe around on those skinny legs," Tilker says.

There are nine species of the chevrotain in South and Southeast Asia, and one species in central Africa. Chevrotains are the smallest ungulates in the world.

Next, the scientists plan to place camera traps in another dry forest region of Vietnam. Eventually they hope to conduct the first-ever comprehensive survey of the species, to assess its population size and distribution.

The researchers can’t yet say how many silver-backed chevrotains are left or where exactly they live; their conservation status remains "data deficient" due to a lack of study. If one or two sites with sizable, stable populations can be identified, then protection measures such as education of local people and anti-poaching patrols can be put in place, Tilker says.

The long-term survival of this species depends on a reduction in snaring and poaching. While Vietnam takes this very seriously, it’s a difficult problem to tackle, says Tilker.

"The rediscovery of the silver-backed chevrotain provides big hope for the conservation of biodiversity, especially threatened species, in Vietnam," said Hoang Minh Duc, head of the Southern Institute of Ecology's Department of Zoology. It will encourage Vietnam, together with international partners, to look for other species and devote additional effort into conserving the country’s biodiversity, he says.

The silver-backed chevrotain is the first mammal re-discovered under a Global Wildlife Conservation program called the Search for Lost Species. This initiative seeks to find some 1,200 animal and plant species that have gone missing to science—and work to protect them. Many of these species aren't exciting or charismatic, says Tilker, and are in need of someone to pay attention.