Turkana boys play with rifles in a village inside the Turkana region of the Ilemi Triangle, northwest Kenya December 21, 2014. The Ilemi Triangle is a disputed region in East Africa, claimed by South Sudan and Kenya, bordering also Ethiopia. The dispute arose from unclear wording of a 1914 treaty which tried to allow free movement of the Turkana people, nomadic herders who had traditionally grazed the area. (Photo by Goran Tomasevic/Reuters)

A winter swimmer, wearing a Santa Claus hat to celebrate the upcoming Christmas, reacts as he plays on a frozen lake at a park in Shenyang, Liaoning province, December 22, 2014. The characters on the hat read: “Shenyang Winter Swimming”. (Photo by Reuters/Stringer)

Tourists play in front of a 3D painting on the wall of a house in Luoyuan village, Jinhua, Zhejiang province, August 26, 2015. The village hired a team to put on 3D paintings all over the valley as a method to attract tourists and improve the income of local villagers, according to local media. (Photo by Reuters/China Daily)

Denver Broncos cheerleaders during the third quarter. The Denver Broncos played the Kansas City Chiefs at Sports Authority Field at Mile High in Denver, Colo. on September 14, 2014. (Photo by Aaron Ontiveroz/The Denver Post via Getty Images)

Hucul horses play in the wild meadows and forests near Odrzychowa in southeastern Poland on October 18, 2014. Huculs, a primitive breed of horse, escaped total extinction due to the efforts of scientists and Polish farmers. (Photo by Janek Skarzynski/AFP Photo)

A Brazil soccer fan wearing contact lenses that mimic the Brazilian flag reacts as she watches her team play Germany in a World Cup semifinal game via live telecast inside the FIFA Fan Fest area on Copacabana beach in Rio de Janeiro, Brazil, Tuesday, July 8, 2014. (Photo by Leo Correa/AP Photo)

Honourable mention, Behaviour category. Toss the scorpion – Indian roller playing with its kill by Susmita Datta. The image was taken during an early morning safari drive at Tadoba Andhari Tiger Reserve in India. (Photo by Susmita Datta/PA Wire/Royal Society Publishing Photography Competition 2017)

A Hawaiian cleaner wrasse provides its cleaning services to a yellowfin goatfish in a reef community off the Big Island in Hawaii. Cleaner species help rid their hosts of ectoparasites, dead tissue, bacteria and fungi. Studies have shown cleaning to play a vital role in keeping many reef ecosystems healthy. (Photo by Marty Snyderman/Caters News Agency)