Zhang Xiang (right) and his mother Zhang Ka in the wild environment in Wolong, Sichuan province, in November 2013. [Photo provided to China Daily]

Zhang Hemin says the researchers at first did not know how to handle the abandonment problem.

So, they settled on a course that was part philanthropy and part trickery.

They would take away the deserted baby and feed it milk.

Then, they would switch it with the favored cub from time to time. So the mother unwittingly supported both.

Researchers also emulated the mother panda in other ways.

The mother would lick different parts of the newborn cub, including its anus to get its droppings out.

So, researchers used a cotton bud to mimic the mother while touching the deserted cub to get the droppings out. This ensured the cubs' survival, Zhang Hemin said.

In a significant development, the International Union for the Conservation of Nature said in early September that China's giant panda had been downgraded from "endangered" to "vulnerable" on a global list of species at risk of extinction, saying evidence from national surveys indicated the previous population decline had been reversed.

But China's State Forestry Administration disagrees saying it is too early to say the giant panda is no longer endangered.

China's fourth panda census showed 1,864 wild pandas and 375 captive pandas worldwide as of the end of 2013. This compares with 1,596 wild pandas and 164 captive pandas worldwide in the third census carried out over 2000-2002.

And 24 of the 33 groups of wild pandas found in the fourth census are endangered, with some groups having fewer than 30 pandas.

Eighteen groups have fewer than 10 pandas each and are in danger of extinction.

Zhang Hemin is against the downgrading but says it shows an acknowledgment of China's achievements in panda breeding.