They're not a fictional species: Mouse deer still roam the Vietnamese woods.
In 2017 and ?? ??? ?? ??2018, biologists set camera traps in Vietnam's coastal forests to potentially spot the evasive species, not seen in 29 years. The plan worked. Researchers from Global Wildlife Conservation, working with the Southern Institute of Ecology, Leibniz Institute for Zoo and Wildlife Research, and the local community, captured 275 photos of the mouse deer, formally called the Silver-backed Chevrotain.
These are the first photos of the chihuahua-sized species alive in the wild, animals first described by scientists in 1910, but last seen in 1990.
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"They're pretty elusive," said Andrew Tilker, Global Wildlife Conservation's Asian species officer.
Tilker suspects these herbivores wisely steer clear of any potential danger in the woods, but scurry out to make their living off of forest vegetation and fruit — when it's safe.
While there's now proof the mouse deer lives, this doesn't mean the population — vulnerable to habitat encroachment like any wild species — is well-numbered or healthy.
"It might be that it's found across a wide part of Vietnam, or this might be one of a couple populations," said Tilker. "We really have no idea."
(Tilker and his team are prudently keeping specific mouse deer locations hidden, should any nefarious interests go looking for them.)
Behold, the mouse deer:
Original image has been replaced. Credit: Mashable 
Original image has been replaced. Credit: Mashable 
Original image has been replaced. Credit: Mashable Earth is teeming with biodiversity, though many critters, like the world's largest bee, go unseen for decades in their remote or niche habitats.
SEE ALSO: The number of species on Earth is uncountableBut little-seen creatures like the mouse deer are out there, persisting — as long as their wild homes remain untrammeled. And scientists suspect that millions of species, especially insects, have yet to be documented by science.
"Go to a rainforest or a coral reef, or any of the wild places left on the planet, and we are simply over our heads, Seabird McKeon, an ecologist at the University of Central Florida, told Mashable earlier this year.
Many species, however, are imperiled, or may become imperiled this century as the tolls of habitat destruction, exploitation, and climate change, amass. The UN estimates that 1 millionanimal and plant species are threatened with extinction.
The elusive mouse deer might be threatened, too.
"We're careful not to assume their species is thriving across a wide area," Tilker said.