In this October 14, 2013 photo, ecology professor Ricardo Freitas catches a broad-snouted caiman to examine, then release back into the water channel in the affluent Recreio dos Bandeirantes suburb of Rio de Janeiro, Brazil. Caimans are like tanks, a very old species with a remarkable capacity for renovation that allows them to survive under extreme conditions where others couldn't, said Freitas, who runs the Instituto Jacare, or the Caiman Institute, which aims to protect the reptiles. (Photo by Felipe Dana/AP Photo)

Iranian mourners cover themselves with mud during Ashoura, marking the death anniversary of Imam Hussein, the grandson of Islam's Prophet Muhammad, at the city of Bijar, west of the capital Tehran, Iran, Thursday, November 14, 2013. Hussein, one of Shiite Islam's most beloved saints, was killed in a 7th century battle at Karbala, Iraq. (Photo by Ebrahim Noroozi/AP Photo)

A giant Uncle Sam balloon is marched down 6th Avenue during the 87th Annual Macy's Thanksgiving Day Parade, Thursday, November 28, 2013, in New York. After fears the balloons could be grounded if sustained winds exceeded 23 mph, Snoopy, Spider-Man and the rest of the iconic balloons received the all-clear from the New York Police Department to fly between Manhattan skyscrapers on Thursday. (Photo by John Minchillo/AP Photo)

Military vehicles surround a wreckage of a trolleybus, in Volgograd, Russia, Monday, December 30, 2013. A bomb blast tore through a trolleybus in the city of Volgograd on Monday morning, killing at least 10 people a day after a suicide bombing that killed at least 17 at the city's main railway station. Volgograd is about 650 kilometers (400 miles) northeast of Sochi, where the Olympics are to be held. (Photo by Denis Tyrin/AP Photo)

“The Independence day”. While on storm chasing expeditions in the Tornado Alley in USA I have encountered many photogenic supercell storms. This photograph was taken while we were approaching the storm near Julesburg, Colorado on My 28th, 2013. The storm was tornado warned for more than one hour, but stayed an LP storm through all its cycles and never produced a tornado, just occasional brief funnels, large hail and some rain. Photo location: Julesburg, Colorado, USA. (Photo and caption by Marko Korošec/National Geographic Photo Contest)

In this September 1, 2015 photo, street artists Jenaro de Rosenzweig, left, and Alejandro Revilla pose for a portrait behind a restaurant's window covered with a mural by artist Francisco Munoz, signed with his artist's name below, in the Roma Norte neighborhood of Mexico City. Rosenzweig and Revilla founded the “Street Art Chilango” cooperative in March 2013, which is filling neighborhoods with public art by local street artists. (Photo by Rebecca Blackwell/AP Photo)

In celebration of the Spring Solstice 2013 and in conjunction with the release of Dreamworks’ 3D animation The Croods – a family animation centered around the first ever pre historic road trip – a giant monument was built at Stonehenge at sunrise on Tuesday March 19, 2013. This marks the first time a modern structure has Ever been allowed on this historic site. (Photo by Flashforwardpublicity.com)

This adorable gallery reveals the astonished expressions of dozens of puppies as they try to gobble up treats flying through the air toward them. Photographer Christian Vieler, 48, has been documenting pooches, with their eyes bulging, mouths wide open and looks of love on their faces, in his studio as part of the project “Dogs Catching Treats” since 2013. (Photo by Christian Vieler/Caters News Agency)