“The Challenge!” Young boy relishes in a game of tug of war before school. Photo location: Lake Titicaca, Peru. (Photo and caption by Paul Heyman/National Geographic Photo Contest)

A picture taken on July 14, 2014 from a Boeing C135 refueling tanker shows two French Rafale fighter planes, flying over the French capital during the annual Bastille Day military parade on the Champs-Elysees in Paris. France has issued an unprecedented invitation to all 72 countries involved in World War I to take part in its annual Bastille Day military parade. (Photo by Franck Pennant/AFP Photo)

Jill Olsen (R) has her picture taken inside a giant cocoon, from the “Falling Skies” TV series, during the 2014 Comic-Con International Convention in San Diego, California July 24, 2014. (Photo by Sandy Huffaker/Reuters)

A Siberian tiger at a photographer for getting too much in its face during the presentation of two new Siberian tigers at Cabarceno Natural Reserve in Cabarceno, northern Spain, 21 July 2014. (Photo by Pedro Puente Hoyos/EPA)

This picture taken on July 25, 2014 shows people cooling off in a waterpark in Suining, southwest China's Sichuan province. Meteorological departments issued an orange alert for high temperature as a heat wave embraces Sichuan province, with temperature of most area topped 37, local media reported. (Photo by AFP Photo)

Animals destined for the stage of Radio City Music Hall in New York on November 13, 1986 are led to the stage door by their co-stars, the Rockettes dancers. A variety of animals, including camels, sheep and donkeys, will star in an annual Christmas production. (Photo by G. Paul Burnett/AP Photo)

A woman looks at a swimmer getting herself warm after the annual Christmas winter swimming competition in the Vltava river in Prague December 26, 2014. (Photo by David W. Cerny/Reuters)

A man dressed in a condom costume walks at Caleta Portales beach, during a summer awareness campaign by the Chilean Corporation for the Prevention of AIDS in Valparaiso city, northwest of Santiago January 9, 2015. (Photo by Rodrigo Garrido/Reuters)