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)

An Indonesian student protester runs after he caught fire while throwing a molotov cocktail towards police during a protest against the new president's decision to hike fuel prices this week in Makassar, South Sulawesi Province November 19, 2014. (Photo by Yusuf Ahmad/Reuters)

Yana Shcherban of Russia looks at the ball after failing to receive it during their FIVB Women's Volleyball World Grand Prix 2014 final round against Japan in Tokyo August 20, 2014. (Photo by Yuya Shino/Reuters)

“Double head vulture”. On the day of windy days during raptors migration some people in my country start to catch these tired raptors, so in this day we go to photograph some raptors and we saw these tow tired vultures, so we start to drag them away from the hunters until they reach a good hidden place, to make them safe until they start a new journey. Photo location: Kuwait. (Photo and caption by Mohd Khorshed/National Geographic Photo Contest)

People are seen in the crowd as Serbian Emir Kusturica & The No Smoking Orchestra performs during the third day of the Mexican musicial festival Vive Latino, at the Foro Sol in Mexico City, on March 29, 2014. (Photo by Alfredo Estrella/AFP Photo)

A woman aims a World War II machine gun at a military show during celebration of the Defenders of the Fatherland Day in St.Petersburg, Russia, Tuesday, February 23, 2016. The day, celebrated in Russia on February 23, honors the nation's military and is a nationwide holiday. (Photo by Dmitri Lovetsky/AP Photo)

Miss Nord-Pas-de-Calais Camille Cerf (C) is congratulated by Miss Ile de France 2014 Margaux Savary (L) and Miss Auvergne 2014 Morgane Laporte after Cerf won the Miss France 2015 beauty contest on December 6, 2014 in Orleans. (Photo by Guillaume Souvant/AFP Photo)

A P-51 Mustang named “Charlotte's Chariot” from the Southern Heritage Air Foundation flies past a cloud of smoke and fire from a nearby battle reenactment during the Wings Over Houston Airshow in Houston, on Saturday, November 1, 2014. Battle reenactments are part of the yearly show held at Ellington Airport. (Photo by Kar Hlava/AP Photo/Bay Area Citizen)