XINING, Aug. 13 -- A zoo on the Qinghai-Tibet Plateau announced on Wednesday that it has successfully bred a pair of rare snow leopard twins, which, unlike their artificially bred peers in China, were raised by their mother instead of zoo staff.

Scientists with the wildlife park in Xining, capital of northwest China's Qinghai Province, said the twins are in good health after getting through the first two months of their life -- a period which sees a high mortality rate among newborns.

Here are some key facts about the endangered animals:

Snow leopards are usually nocturnal and live between 3,000 and 5,500 meters above sea level in the rocky mountains and plateaus of central and south Asia.

The animal has rarely been seen in the wild since last century due to loss of their habitats and poaching. An estimated 3,500 to 7,000 snow leopards live in the wild, in addition to 600 to 700 more in zoos around the world.

More than half of the wild snow leopards live high up in the remote mountains of northwest Xinjiang, Tibet, Qinghai, Gansu, Yunnan, Sichuan and Inner Mongolia in China, according to the International Snow Leopard Trust.

Snow leopards are white, yellowish, or smoky-gray with dark-gray to black spots. The average life span of a wild snow leopard is 10 years, while those who live in captivity can survive at least 15 years.

They are well adapted for their severe environment. They are smaller than big cats, generally weighing between 28 and 55 kg. The body length is around 75 to 130 cm, and tails are typically about the same length again.

The cat is generally a crepuscular hunter and its main prey consists of wild sheep, goats, musk deer, marmots, hares and birds.

Due to their inherently rare and mysterious character, these critically endangered mammals, scientifically known as uncia, are rarely seen by people. Researchers and conservationists have to work very hard to track them down.

"Some people call snow leopards "hermits on the plateaus." That's an apt phrase to reflect their solitary nature. "It can take years for scientists to shoot a picture of them in the wild," said Qi Xinzhang, deputy chief of the Xining Wildlife Park.

The big cats' bite may be worse than their bark. The animals known to locals as "king of the snow mountains" can't give a full, deep roar because of the underdeveloped fibroelastic tissue that forms part of the vocal apparatus.

The snow leopard was listed as endangered by the International Union for the Conservation of Nature and Natural Resources in 1972. It is also given the highest level of state protection in China, on a par with that given to the giant panda.

The Xining Wildlife Park established an artificial breeding base in 2009 to try to pluck the leopards from the point of extinction. It now has eight adult leopards, the largest artificially raised population in China.

The last time the park saw the birth of snow leopard cubs was in 2012, when a pair of twins, a male and a female, was born.