An elephant bull charges a female hippopotamus as her calf scampers to safety, in Erindi Private Game Reserve in Windhoek, Namibia. (Photo by Rian van Schalkwyk/Barcroft Media)

Boeing B-29 (#10) from the 24th Bomb Squadron, 6th Bomb Group after an emergency landing at Iwo Jima on April 24,1945. (Photo by U.S. Air Force)

Polar Bear club swimmers take their annual swim in the sea at Coney Island in New York City on January 1, 2014. (Photo by Curtis Means/ACE/INFphoto.com)

Two men fight in San Jose, Costa Rica, during the Women's Day on March 8, 2014. (Photo by Jeffrey Arguedas/EFE/SIPA Press)

A woman sits with a Great Dane during the first day of the Crufts dog show in Birmingham, central England March 6, 2014. (Photo by Darren Staples/Reuters)

A Mai-Mai rebel soldier shows off his guns at a checkpoint near the Mugunga refugee camp in Zaire; 1996. (Photo by Carol Guzy/The Washington Post)

Planes land in fog at Heathrow Airport, west London, as heavy fog covers a many parts of the south east, on April 1, 2014. (Photo by Steve Parsons/PA Wire)

Soviet Army soldiers sit on their tanks in front of the Czechoslovak Radio station building in central Prague during the first day of Soviet-led invasion to then Czechoslovakia on August 21, 1968. (Photo by Libor Hajsky/Reuters)