Breeders hold panda cubs at the Chongqing Zoo in southwest China's Chongqing on Jan. 21, 2020. Four panda cubs named Shuangshuang, Chongchong and Xixi, Qingqing, together with the 37-year-old giant panda Xinxing, posed for a Chinese New Year greeting at the Chongqing Zoo. (Photos: Xinhua/Tang Yi)

Panda cubs play at the Chongqing Zoo in southwest China's Chongqing on Jan. 21, 2020. Four panda cubs named Shuangshuang, Chongchong and Xixi, Qingqing, together with the 37-year-old giant panda Xinxing, posed for a Chinese New Year greeting at the Chongqing Zoo.

A panda cub plays at the Chongqing Zoo in southwest China's Chongqing on Jan. 21, 2020. Four panda cubs named Shuangshuang, Chongchong and Xixi, Qingqing, together with the 37-year-old giant panda Xinxing, posed for a Chinese New Year greeting at the Chongqing Zoo.

Breeders present a "gift" to giant panda Xinxing at the Chongqing Zoo in southwest China's Chongqing on Jan. 21, 2020. Four panda cubs named Shuangshuang, Chongchong and Xixi, Qingqing, together with the 37-year-old giant panda Xinxing, posed for a Chinese New Year greeting at the Chongqing Zoo.

Giant panda Xinxing plays at the Chongqing Zoo in southwest China's Chongqing on Jan. 21, 2020. Four panda cubs named Shuangshuang, Chongchong and Xixi, Qingqing, together with the 37-year-old giant panda Xinxing, posed for a Chinese New Year greeting at the Chongqing Zoo.

Panda cubs play at the Chongqing Zoo in southwest China's Chongqing on Jan. 21, 2020. Four panda cubs named Shuangshuang, Chongchong and Xixi, Qingqing, together with the 37-year-old giant panda Xinxing, posed for a Chinese New Year greeting at the Chongqing Zoo.

Giant panda Xinxing eats at the Chongqing Zoo in southwest China's Chongqing on Jan. 21, 2020. Four panda cubs named Shuangshuang, Chongchong and Xixi, Qingqing, together with the 37-year-old giant panda Xinxing, posed for a Chinese New Year greeting at the Chongqing Zoo.