A lost species known as the “mouse deer’” has been spotted for the first time since 1990.

The “shy and solitary” silver-backed chevrotain, which is the size of a rabbit and has two tiny fangs, was last recorded more than 25 years ago. It was since thought to have been lost by snare poaching in Vietnam.

The discovery, published Monday in the journal Nature Ecology and Evolution, was made by a team of researchers who set up a series of “camera traps” for five months in a southern region of Vietnam where locals said they may have spotted the deer-like creature with grey fur. The colour distinguishes it from “more common lesser” mouse deer, according to researchers.

It is the first mammal rediscovered as part of a Global Wildlife Conservation project to find lost species.

"For so long, this species has seemingly only existed as part of our imagination," said An Nguyen, associate conservation scientist for GWC and expedition team leader, in a statement. “Discovering that it is, indeed, still out there, is the first step in ensuring we don't lose it again, and we're moving quickly now to figure out how best to protect it."

Scientists know little about the species, which was first described in 1910 after four of them were discovered in southern Vietnam. A fifth was collected in central Vietnam in 1990 before mouse deer were thought to be lost.

“The rediscovery of the silver-backed chevrotain provides a 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, in a statement.

“This also encourages us, together with relevant and international partners, to devote time and effort to further investigate and conserve Vietnam's biodiversity heritage.”

The mouse deer are neither mouse or deer, but the smallest of small hoofed mammals known as “ungulates.” Scientists are now setting up a wide survey of the area to determine how stable and populous the silver-backed chevrotains are in Vietnam.

"It is an amazing feat to go from complete lack of knowledge of the wildlife of the Greater Annamites 25 years ago to now having this question mark of the silver-backed chevrotain resolved," said Barney Long, GWC senior director of species conservation, in a statement.

The team of researchers have also released accompanying illustrations by artist Eric Losh depicting the discovery.