Silver-backed chevrotains have been ‘rediscovered’ by science after 29 years

With help from Vietnamese villagers, researchers captured photos of the deerlike ungulate

silver-backed chevrotain

The silver-backed chevrotain, endemic to Vietnam, was “rediscovered” after 29 years by scientists who teamed up with locals to capture photographic evidence of the deerlike ungulate.

Southern Institute of Ecology, Global Wildlife Conservation, Leibniz Institute for Zoo and Wildlife Research, NCNP

Amidst the dry, thorny underbrush of a coastal Vietnamese forest, a silver-backed chevrotain stepped into view of a camera trap — and back into the scientific record after almost three decades.

The deerlike ungulate, no bigger than a toy poodle, had only ever been studied from dead specimens, four obtained in 1907 and one in 1990. Scientists feared the animal might have gone extinct due to hunting and habitat loss.

But local residents knew better, and in late 2017 directed researchers to forest areas where the silver-backed chevrotain (Tragulus versicolor) might be living. Cameras triggered by motion or heat then snapped the first photographic evidence that the elusive animal still exists, according to a study published online November 11 in Nature Ecology and Evolution.

“We were really excited” by the find, says An Nguyen, a biologist at the Leibniz Institute for Zoo and Wildlife Research in Berlin. The region’s forests are home to many mammals found nowhere else, but an increase in animal traps and encroaching human development in recent decades have put that diversity under threat.

Researchers captured 208 images to confirm the silver-backed chevrotain (pictured) still lived in the wild in Vietnam. They know there’s more than one, as this image shows, but the size of the population is unclear.Southern Institute of Ecology, Global Wildlife Conservation, Leibniz Institute for Zoo and Wildlife Research, NCNP

“Indiscriminate snaring has taken a tremendous toll on mammal communities across Vietnam,” says Andrew Tilker, also a biologist at the Leibniz Institute. Snaring has left “a lot more forest than animals to inhabit it in Vietnam,” he says.

But a species lost to science is not necessarily extinct. So Nguyen and colleagues visited towns and villages near the southeast city of Nha Trang in the fall of 2017 to ask people about the animal. “‘Had they seen chevrotain with silver backs? How many? Where?’” Nguyen says in recalling the researchers’ questions to locals. People referred to both the silver-backed chevrotain and its more common cousin, the lesser chevrotain, by the same name, “cheo cheo.” But many reported seeing the distinctive silver-haired chevrotain.

The team set up cameras at three spots in the forest where silver-backed chevrotain had been spotted. The first images of the silver-backed chevrotain were discovered when the team collected the cameras five months later.

After adding 30 more camera traps, the team ended up with a total of 1,881 images that documented 208 separate, daytime visits, mostly by individual creatures but occasionally by pairs. It’s unclear how many individuals were photographed, or whether the animals were part of a larger population. “We just can’t tell with these cameras,” Nguyen says.

A camera trap captures video of a silver-backed chevrotain scouring the forest floor. Little is known about the biology of this species, as scientists have described it only from dead specimens. 

The villagers weren’t surprised that the animals had been spotted, Nguyen says. “They see them all the time,” he says, though many reported the animals’ numbers had declined in recent years.

The research “emphasizes the critical value of integrating local ecological knowledge into biodiversity conservation efforts,” says Patricia Fifita, an environmental anthropologist at the University of Hawaii at Manoa who was not involved in the research.

Tilker agrees, noting that villagers’ help proved crucial to the researchers’ success in this study. “Local people often have a vast reservoir of ecological knowledge that just isn’t available to any scientists,” he says.

Without more research and population-level data, the future of the silver-backed chevrotain is unclear. If the species exists only in this part of Vietnam, it could be highly threatened, Tilker says. “Right now it’s just a question mark.”

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