– The panda cub snuffles, stretches out a tiny paw and snuggles with his mother, Cao Cao. She stirs, sniffs him gently and gives him a lick as they rest in her maternity enclosure at the Hetaoping Wilderness Training Base in the mist-wreathed mountains of southwestern China.

The cub, 2 months old and too small to be named, is the size of a house cat. He and his sister are rare genetic treasures, the first twin giant panda cubs born to a wild male panda and a female sent back into the wild to mate.

In the past two years, Cao Cao, a mother of nine, has given birth to the only three progeny of an ambitious return-to-nature program that Chinese scientists hope will save the species from extinction. Cao Cao, 16, was born in the wilds herself before being taken into captivity in Sichuan when she was about 13 months old.

One of her male cubs, Tao Tao, was released in 2012 and has since been recaptured twice for health checks. Researchers believe Tao Tao may have sired a cub, but they will have to wait until the cub is an adult to do DNA testing.

Wild pandas, once found in 17 provinces, now survive in just three. Their habitat is fragmented, with 73 percent in groups so small there is a strong chance they will not survive, said a 2017 report from Beijing Forestry University.

In the 1970s, the panda population dipped to about 1,000. In response, the Chinese government spent tens of millions of dollars to establish training centers and forest reserves, helping the numbers recover to roughly 2,200. Of those, 25 percent reside in the scientific centers, zoos or other such facilities.

The roly-poly celebrities are replete with political and cultural significance, and economic value as a tourism draw. So to ensure their long-term survival, China has initiated a make-or-break experiment sending captive pandas into the wild permanently to boost fragile populations scattered in six isolated mountainous regions.

Equally vital is a plan for a 5 million-acre conservation park — twice the size of Yellowstone National Park — financed by the Bank of China at a cost of $1.1 billion. Researchers hope the park, set for completion by 2023, will ensure the successful release of dozens of captive-bred pandas to re-establish wild populations in areas that have not seen them for decades.

The Hetaoping base, where Cao Cao usually resides, has released four captive-bred females since 2016 in hopes that they would mate with wild males. Cao Cao is the only one with a confirmed pregnancy.

At Hetaoping, cubs are prepared for release largely without human contact. They are raised by their mothers until independent, then moved to larger isolated compounds. Their only interaction with humans is with the keepers who deliver bamboo daily, dressed in panda suits soaked in panda urine to cover the human smell.

A second center — Chengdu Research Base of Giant Panda Breeding in the Sichuan capital, Chengdu — has taken the opposite approach. At Chengdu, operated in collaboration with Virginia-based Global Cause Foundation, humans train the bears to eat, climb trees and find water, making it easier to intervene when they are injured or sick.

The problem is that whatever the approach, the release of pandas can prove physically dangerous (for the pandas) and politically delicate (for the humans), since the public reacts with outrage to any sort of panda suffering or fatalities.

Of 11 pandas thus far released permanently by the centers, three have died and a fourth, Qian Qian (pronounced Chen Chen), got sick and would have died had she not been rescued, her story the focus of a recent IMAX movie, “Pandas.”

“In some places the wild population is less than 30, in some less than 20,” said Zhang Hemin, deputy director of the China Conservation and Research Center for the Giant Panda, which runs the Hetaoping base as well as a facility in Dujiangyan. “If we don’t help them, they’ll be extinct within the next 30 to 50 years.”

He called Cao Cao a “hero mother,” having given birth to three sets of twins and three others.

Three young pandas from multiple mothers are now being prepared for release from Hetaoping. The reintroduction plan cannot be considered a success until pandas not only survive but also reproduce and raise wild cubs that survive and reproduce.

“That is the biggest challenge for us,” Zhang said. “We spent almost 50 years to successfully breed pandas in captivity. Maybe it will take another 50 years to reintroduce captive pandas into the wild.”