An alpaca chewing a leaf is pictured on November 18, 2014 in the zoo of Frankfurt am Main, Germany. (Photo by Frank Rumpenhorst/AFP Photo/DPA)

American soldiers leaping from an armoured personnel carrier during exercises in Korea, 17th March 1954. (Photo by Three Lions)

A small section of the expanding remains of the Veil Nebula, a massive star that exploded about 8,000 years ago. The entire nebula is 110 light-years across, covering six full moons on the sky as seen from Earth, and resides about 2,100 light-years away in the constellation Cygnus, the Swan. (Photo by Reuters/NASA/ESA/Hubble)

Black-headed gulls sit on pickets at a riverside in Tokyo, Japan, December 27, 2015. (Photo by Toru Hanai/Reuters)

Costumed participants are seen during an Irish tradition of Hunting of the Wren festival held every St. Stephen's Day in Dingle, Ireland, December 26, 2016. Wren Day, also known as Wren's Day, Day of the Wren, or Hunt the Wren Day is celebrated on 26 December, St. Stephen's Day. The tradition consists of “hunting” a fake wren and putting it on top a decorated pole. (Photo by Clodagh Kilcoyne/Reuters)

A rabbit fails to jump over an obstacle during a rabbit track and field competition on the sidelines of a hunting exhibition in Kromeriz, about 60 km east of Prague, on April 1, 2017. Circa 100 rabbits took part in the competition, including disciplines as long jump, high jump and running on a flat track. (Photo by Radek Mica/AFP Photo)

Medic James E. Callahan of Pittsfield, Mass., gives mouth-to-mouth resuscitation to a dying soldier in war zone D, about 50 miles northeast of Saigon, June 17, 1967. Thirty-one men of the 1st Infantry Division were reported killed in the guerrilla ambush, with more than 100 wounded. (Photo by Henri Huet/AP Photo)

In this September 10, 1977, file photo, from left, Hua Guofeng, Chinese Communist Party (CCP) chairman and Mao Zedong's immediate successor; Ye Jianying, CCP vice chairman and future ceremonial head of state; Deng Xiaoping, no formal titles at the time but soon to emerge as paramount leader during the reform era; Li Xiannian, CCP vice chairman and future president; Wang Dongxing, head of the leadership bodyguard unit who helped topple the Gang of Four, view the body of later Chinese leader Mao Zedong in Beijing. (Photo via AP Photo)