Siberian tigers play at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 22, 2018. (Xinhua/Wang Jianwei)

A Siberian tiger climbs the tree at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 21, 2018. (Xinhua/Wang Jianwei)

A Siberian tiger is seen at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 21, 2018. (Xinhua/Wang Jianwei)

Siberian tigers play at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 22, 2018. (Xinhua/Wang Jianwei)

Siberian tigers play at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 21, 2018. (Xinhua/Wang Jianwei)

Siberian tigers play at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 21, 2018. (Xinhua/Wang Jianwei)

Siberian tigers play at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 21, 2018. (Xinhua/Wang Jianwei)

A Siberian tiger stands in the snow at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 22, 2018.(Xinhua/Wang Jianwei)

A Siberian tiger is seen at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 21, 2018. (Xinhua/Wang Jianwei)

Siberian tigers play at the China Hengdaohezi Feline Breeding Center in Hailin City, northeast China's Heilongjiang Province, Nov. 21, 2018. (Xinhua/Wang Jianwei)