A giant panda cub rests at Zoo Berlin in Berlin, capital of Germany, May 28, 2020. Zoo Berlin reopened to the public on April 28 after a closure for more than a month due to COVID-19. Giant pandas "Meng Meng", "Jiao Qing" from China and their twin cubs "Meng Xiang", "Meng Yuan" have attracted numerous visitors though restrictions are still imposed in the zoo. (Photo by Binh Truong/Xinhua)

A giant panda cub plays at Zoo Berlin in Berlin, capital of Germany, May 28, 2020. Zoo Berlin reopened to the public on April 28 after a closure for more than a month due to COVID-19. Giant pandas "Meng Meng", "Jiao Qing" from China and their twin cubs "Meng Xiang", "Meng Yuan" have attracted numerous visitors though restrictions are still imposed in the zoo. (Photo by Binh Truong/Xinhua)

Giant panda "Meng Meng" is seen at Zoo Berlin in Berlin, capital of Germany, May 28, 2020. Zoo Berlin reopened to the public on April 28 after a closure for more than a month due to COVID-19. Giant pandas "Meng Meng", "Jiao Qing" from China and their twin cubs "Meng Xiang", "Meng Yuan" have attracted numerous visitors though restrictions are still imposed in the zoo. (Photo by Binh Truong/Xinhua)

Giant panda "Meng Meng" is seen at Zoo Berlin in Berlin, capital of Germany, May 28, 2020. Zoo Berlin reopened to the public on April 28 after a closure for more than a month due to COVID-19. Giant pandas "Meng Meng", "Jiao Qing" from China and their twin cubs "Meng Xiang", "Meng Yuan" have attracted numerous visitors though restrictions are still imposed in the zoo. (Photo by Binh Truong/Xinhua)

Giant panda "Meng Meng" is seen at Zoo Berlin in Berlin, capital of Germany, May 28, 2020. Zoo Berlin reopened to the public on April 28 after a closure for more than a month due to COVID-19. Giant pandas "Meng Meng", "Jiao Qing" from China and their twin cubs "Meng Xiang", "Meng Yuan" have attracted numerous visitors though restrictions are still imposed in the zoo. (Photo by Binh Truong/Xinhua)

A giant panda cub rests at Zoo Berlin in Berlin, capital of Germany, May 28, 2020. Zoo Berlin reopened to the public on April 28 after a closure for more than a month due to COVID-19. Giant pandas "Meng Meng", "Jiao Qing" from China and their twin cubs "Meng Xiang", "Meng Yuan" have attracted numerous visitors though restrictions are still imposed in the zoo. (Photo by Binh Truong/Xinhua)

A giant panda cub plays at Zoo Berlin in Berlin, capital of Germany, May 28, 2020. Zoo Berlin reopened to the public on April 28 after a closure for more than a month due to COVID-19. Giant pandas "Meng Meng", "Jiao Qing" from China and their twin cubs "Meng Xiang", "Meng Yuan" have attracted numerous visitors though restrictions are still imposed in the zoo. (Photo by Binh Truong/Xinhua)

Giant panda "Meng Meng" is seen at Zoo Berlin in Berlin, capital of Germany, May 28, 2020. Zoo Berlin reopened to the public on April 28 after a closure for more than a month due to COVID-19. Giant pandas "Meng Meng", "Jiao Qing" from China and their twin cubs "Meng Xiang", "Meng Yuan" have attracted numerous visitors though restrictions are still imposed in the zoo. (Photo by Binh Truong/Xinhua)