Giant panda Bei Bei walks towards his frozen 4th birthday cake at the Smithsonian National Zoo in Washington, DC, on August 22, 2019. Bei Bei is set to move to China after turning four years old, according to a US-China breeding agreement between the Smithsonian National Zoo and the China Wildlife Conservation Association. (Photo/Agencies)

Giant panda Bei Bei eats his frozen 4th birthday cake at the Smithsonian National Zoo in Washington, DC, on August 22, 2019. Bei Bei is set to move to China after turning four years old, according to a US-China breeding agreement between the Smithsonian National Zoo and the China Wildlife Conservation Association.(Photo/Agencies)

Giant panda Bei Bei walks towards his frozen 4th birthday cake at the Smithsonian National Zoo in Washington, DC, on August 22, 2019. Bei Bei is set to move to China after turning four years old, according to a US-China breeding agreement between the Smithsonian National Zoo and the China Wildlife Conservation Association. (Photo/Agencies)