Participant wearing medieval costumes perform during an annual re-enactment of a battle near the village of Libusin, Czech Republic, April 23, 2016. About 2000 enthusiasts have come to simulate the medieval battle during the 24rd annual swordsmen gathering in Libusin village. (Photo by David W. Cerny/Reuters)

A four-legged robot dog called SPOT patrols a park as it undergoes testing to be deployed as a safe distancing ambassador, following the coronavirus disease (COVID-19) outbreak, in Singapore on May 8, 2020. (Photo by Edgar Su/Reuters)

Warriors from the Suri tribe in Ethiopia still stage the savage “Donga” battles – even after many fighters have been died from their injuries. Donga stick fights take place after the harvests, the Surmas count days owing to knots on a long stem of grass or jags on the trunk of a tree dedicated to that specific use. Here: A tribeswoman sporting a huge lip plate and wearing a skinned animal carcass on her head. (Photo by Eric Lafforgue/Exclusivepix Media)

A goat named “White On The Right” bleats as it is paraded with other goats prior to a race during the annual Easter goat racing event at the Mount Pleasant recreation ground in Tobago April 6, 2015. (Photo by Andrea De Silva/Reuters)

Chacha, the male chimp, screams at a worker in Sendai, northern Japan, Thursday, April 14, 2016 after fleeing from a zoo. The chimpangzee tried desperately to avoid being captured by climbing an electric pole. Chacha was on the loose nearly two hours Thursday after it disappeared from the Yagiyama Zoological Park in Sendai, the city that's hosting finance ministers from the Group of Seven industrialized nations in May. (Photo by Kyodo News via AP Photo)

A Typhoon jet flown by Flt Lt Jim Peterson practising over RAF Coningsby in the East Lindsey district of Lincolnshire, England on September 27, 2019 producing a rainbow effect over the plane. The rainbow is made of crystalized or frozen water vapor that reflect and refract sunlight, causing the rainbow effect. (Photo by Claire Hartley/Bav Media)

The pedestrian zone on the banks of the “Parco della Pace” at Lake Maggiore is flooded due to flooding, on Thursday, October 24, 2019 in Locarno, Switzerland. (Photo by Samuel Golay/Ti-Press/Keystoen)

A boat commutes across the Mekong river in Phnom Penh on August 8, 2014. The Mekong is the world's twelth longest river running from the Tibetan Plateau through China's Yunnan province, Myanmar, Laos, Thailand, Cambodia and Vietnam. (Photo by Tang Chhin Sothy/AFP Photo)