Australian scientists have found one of the world’s rarest mammals living high in the Himalayan mountains.

The squirrel is more than a metre long, weighs 2.5 kilograms and has been known to scientists for almost 130 years but was previously thought to be a single, rare species living mostly in remote valleys in Pakistan.

Now researchers from Australia and China have shown that two related species of gigantic, woolly flying squirrels, both previously unknown to science, live in India and China.

Led by Australian Museum chief scientist Professor Kristofer Helgen and research associate Dr Stephen Jackson, the findings were published on Monday in the Zoological Journal of the Linnean Society.

Using the handful of museum specimens of woolly flying squirrels available, with data from field expeditions, the team confirmed that these huge, fluffy squirrels form three widely separated populations of distinct species, two of which are described as new species.

These have been named the Tibetan woolly flying squirrel (eupetaurus tibetensis) and the Yunnan woolly flying squirrel (eupetaurus nivamons).

Professor Helgen said comparative research in museum collections, along with new fieldwork, often led zoologists to species that were new to science, even new mammals.

But even Professor Helgen was surprised by the latest discoveries.

“These are some of the largest squirrels in the world, so it is pretty surprising that it has taken until 2021 for them to get their scientific names,” she said.

“The two new species are gorgeous, soft-furred squirrels that are genetically and anatomically very different from all other squirrels. And they live on top of the world – in the Himalayas and on the Tibetan plateau,” she said.

Dr Jackson said the squirrels lived at altitudes up to 4800 metres (or more than half the height of Mount Everest), occur largely in areas uninhabited by people, and are some of the least known animals in the world, with only a handful of people having seen the mammal glide.

“At over one metre in length with a thick pelt of silky fur, the squirrel is one of the largest in the world. It is a nocturnal animal, with a huge furry tail like a fox,” he said.

Populations of woolly flying squirrels had previously been suspected to occur in China, but documentation was lacking.

The eastern Himalayan region where the Yunnan woolly flying squirrel was discovered is the intersection of three global biodiversity hotspots: the Himalayas, the mountains of south-west China, and Indo-Burma.

The other new species, the Tibetan woolly flying squirrel, is known from the southern Tibetan plateau, in the Tibetan Autonomous Region of China and the Indian state of Sikkim.

Most specimens of this species were collected more than 50 years ago but have been largely overlooked in museums.

Scientists are hoping that populations of the Tibetan woolly flying squirrel still occur in high elevation areas of China, India, and Bhutan.

All three species of giant woolly flying squirrels live near the tree line, above 2400 metres elevation.

“Very little remains known about them so far, but they have highly specialised teeth and are known to feed on pine needles, a very unusual diet, and rest in rocky crevices,” Dr Jackson said.

“Though they live in remote areas, all species are potentially affected by hunting, habitat loss, and warming climates,” he said.