A child rescued from Boko Haram in Sambisa forest is seen at the Internally Displaced People's camp in Yola, Nigeria May 3, 2015. Hundreds of traumatised Nigerian women and children rescued from Boko Haram Islamists have been released into the care of authorities at a refugee camp in the eastern town of Yola, an army spokesman said. (Photo by Afolabi Sotunde/Reuters)

A former paratrooper demonstrates his strength and skills while lifting a chair during the celebrations for the Paratroopers Day at the Central park in the Siberian city of Krasnoyarsk, Russia, August 2, 2015. Paratroopers are an elite unit of the Soviet Army, and everyone in the country recognize their blue berets. (Photo by Ilya Naymushin/Reuters)

A jaguar ambushes a giant jacare caiman high up on the Three Brothers River in the Pantanal in Mato Grosso, Brazil. The cat wrestled with the reptile for over twenty minutes in a death struggle witnessed by photographer Chris Brunskill just after ten o'clock in the morning on the 26th of September, 2017. Caimans form a large part of the jaguar's diet in the Pantanal but battles such as this are very rarely observed and seldom photographed. (Photo by Chris Brunskill Ltd/Getty Images)

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)

For centuries the Highlands peoples of Papua New Guinea fought over land, women and pigs. Sorcery and battle skills could elevate a clan to Bigmanship, where the bigger the “presentation”, the bigger the man. Clans therefore would paint their bodies and create fearsome masks as part of their psy. Here: These are the terrifying tribe of “mudmen” from a remote part of Papua New Guinea. (Photo by Jeremy Hunter/Exclusivepix Media)

A member of the Acorda Capoeira (Awaken Capoeira) group performs on a rooftop in the Rocinha favela in Rio de Janeiro, Brazil, July 24, 2016. In a favela with a history of violence between police and drug gangs, or armed battles between traffickers themselves, capoeira is an outlet that gives kids a sense of community – its practice a collective exercise blending characteristics of drum circles, sparring and tag-team gymnastics. (Photo by Bruno Kelly/Reuters)

Patients from Rady Children's Hospital hug a bottlenose dolphin after being invited to swim and interact with dolphins at Sea World in San Diego, California August 27, 2015. Sea World has hosted Dolphin Interaction Program for seven years. It was started by dolphin trainer Joy Soto who battled and overcame non-Hodgkin’s lymphoma. (Photo by Mike Blake/Reuters)

A naked Hindu holy man arrives to bath in the Godavari River during Kumbh Mela, or Pitcher Festival, at Trimbakeshwar in Nasik, India, Saturday, August 29, 2015. Hindus believe taking a dip in the waters of a holy river during the festival, will cleanse them of their sins. According to Hindu mythology, the Kumbh Mela celebrates the victory of gods over demons in a furious battle over a nectar that would give them immortality. (Photo by Rajanish Kakade/AP Photo)