A girl walks in front of a graffiti painted on the wall of a house located inside the 15th-century complex built by Mameluk Sultan al-Ashraf Qaitbey, in Cairo's City of the Dead, Egypt February 13, 2017. (Photo by Amr Abdallah Dalsh/Reuters)

Actress Laetitia Casta attends the “The Meyerowitz Stories” screening during the 70th annual Cannes Film Festival at Palais des Festivals on May 21, 2017 in Cannes, France. (Photo by Stephane Mahe/Reuters)

A police officer stands at a police cordon near the scene of a terror attack in London, U.K., on Sunday, June 4, 2017. A van swerved into Saturday-night crowds on London Bridge, before three men got out and went on a stabbing rampage through nearby bars. (Photo by Luke MacGregor/Bloomberg)

A mural signed by “TV Boy” and depicting Pope Francis and U.S. President Donald Trump kissing, is seen on a wall in downtown Rome, Italy on May 11, 2017. (Photo by Tony Gentile/Reuters)

Members of the China Disabled Peoples Performing Art Troupe perform “My Dream” at Jorge Eliecer Gaitan Theater in Bogota on August 30, 2017. China Disabled People's Performing Art Troupe Company composed of artists with some hearing, mental, motor, visual or speech disabilities, was founded in 1987 and is currently Honorary and Goodwill Ambassadors of Unesco for its great example of inclusion. (Photo by John Vizcaino/AFP Photo)

The “Rabid Transit” Burning Man art car erupts with flames from it's onboard propane poofers during the 4th day of the annual Burning Man arts and music festival in the Black Rock Desert of Nevada, U.S., August 31, 2017. (Photo by Jim Bourg/Reuters)

Eva Longoria Farmer Visits "The Tonight Show Starring Jimmy Fallon" at Rockefeller Center on November 24, 2015 in New York City. (Photo by Theo Wargo/NBC/Getty Images for "The Tonight Show Starring Jimmy Fallon")

Behaviour: Mammals category. Giant Gathering by Tony Wu, USA. Dozens of sperm whales mingled noisily off Sri Lanka’s northeast coast, stacked as far down as Tony could see. This was a congregation of dozens of social units, like a gathering of the clans. Aggregations like this could be a critical part of the whales’ rich social lives but are rarely reported. Some two thirds of the population was wiped out before commercial whaling was banned in 1986. This kind of major gathering could be “a sign that populations are recovering”, says Tony. (Photo by Tony Wu/Wildlife Photographer of the Year 2017)