Scientists donned panda suits again yesterday for the historic transfer of giant panda Cao Cao and her cub Cao Gen to the outer ring of China’s Wolong Nature Reserve. Cao Gen became the first panda cub born in a semi-natural environment to be released into the semi-wild.

(Listen for Cao Gen’s bark when the basket cover is lifted at the end of the clip.)

Researchers decided to move the pandas after reports that Cao Gen had been exhibiting wild instincts, snarling at humans during his physical examinations. In the wild, these instincts help pandas defend themselves against threats from predators such as leopards.

Acting on a suggestion by panda expert Hu Jinchu, the Wolong reserve’s directors recently announced that the bears’ keepers will periodically dress up in leopard costumes and roar at the pandas to further encourage their survival instincts.

Cao Cao and Cao Gen’s new environment is situated at an elevation of 2,200 meters above sea level and measures 40,000 square meters. Fences around the area are specially-designed to ensure the pandas’ safety from other animals and to prevent them from escaping.