In this March 18, 2015 photo, a boy rides a mechanical bull for children at the Texcoco Fair on the outskirts of Mexico City. In Mexico, these types of fairs date back to Spanish colonial times, and in some smaller communities they are organized around the feast days of Roman Catholic saints. (Photo by Eduardo Verdugo/AP Photo)

Members of the Jordanian police women's team attend the 7th Annual Warrior Competition at the King Abdullah Special Operations Training Center in Amman April 22, 2015. Thirty-eight teams from 18 countries are participating in the competition to test their military skills. (Photo by Muhammad Hamed/Reuters)

National Geographic photographer Steve Winter has spent most of his adult life shooting wild cats. Photo: A 14-month-old cub, cooling off in a pond, is riveted by a deer that appeared near the shore. Tigers are powerful swimmers; they can easily cross rivers four to five miles wide and have been known to swim distances of up to 18 miles. (Photo by Steve Winter/National Geographic)

The painted nails of a Kurdish Peshmerga female fighter are seen as she takes up a position during combat skills training before being deployed to fight Islamic State militants, at their military camp in Sulaimaniya, northern Iraq September 18, 2014. (Photo by Ahmed Jadallah/Reuters)

“The Africanis is a landrace of South African dogs. It is believed to be of ancient origin, directly descended from hounds and pariah dogs of ancient Africa, introduced into the Nile Valley from the Levant. The Swahili name for the breed is umbwa wa ki-shenzi meaning common or mongrel or “traditional dog”. Africanis is also an umbrella name for all the aboriginal dogs in southern Africa”. – Wikipedia. Photo: Africanis 18. Murraysburg, Western Cape, May 10, 2010. (Photo by Daniel Naudé)

Shane Baker of Minnesota poses for a photo with adult film actress Rachel Starr at the Pornhub booth at the 2017 AVN Adult Entertainment Expo at the Hard Rock Hotel & Casino on January 18, 2017 in Las Vegas, Nevada. (Photo by Ethan Miller/Getty Images)

Marco Antonio Eguchi of Brazil gets bucked off of Bottoms Up in the first round of the PBR Frontier Communications Iron Cowboy at AT& T Stadium on February 18, 2017 in Arlington, Texas. (Photo by Tom Pennington/Getty Images)

A boy moves away as a United Nations World Food Programme (WFP) helicopter lands in Rubkuai village, Unity State, northern South Sudan, February 18, 2017. South Sudan on Monday declared famine in some parts of the country, with more than three years of war leaving nearly five million hungry in what aid groups called a “man-made” tragedy. (Photo by Siegfried Modola/Reuters)