Giant panda Ding Ding enjoys a birthday meal at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Meng Jing)

Giant panda Ding Ding plays with a toy at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Meng Jing)

Giant panda Ding Ding enjoys a birthday meal at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Meng Jing)

Visitors look at giant panda Ding Ding at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Giant panda Ding Ding feeds on bamboos at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Giant panda Ru Yi enjoys a birthday meal at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Visitors look at giant panda Ru Yi at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Giant panda Ru Yi enjoys a birthday meal at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Visitors look at giant panda Ding Ding at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Giant panda Ding Ding feeds on bamboos at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Giant panda Ru Yi enjoys a birthday meal at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Visitors look at giant panda Ru Yi at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Visitors look at giant panda Ding Ding at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Giant panda Ding Ding enjoys a birthday meal at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)

Giant panda Ru Yi enjoys a meal at the Moscow Zoo in Moscow, capital of Russia, on July 31, 2022. The Moscow Zoo on Sunday celebrated the birthdays of two giant pandas Ding Ding and Ru Yi. Six-year-old male Ru Yi was born on July 31, 2016 whereas five-year-old female Ding Ding was born on July 30, 2017. The pair arrived in Moscow in 2019 from China's southwestern province of Sichuan for a 15-year joint research program. (Xinhua/Bai Xueqi)