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)

A young Bengal tiger cub smuggled into the US and seized at the Mexico border is displayed for the media during Operation Jungle Book at the US Fish and Wildlife Service in Torrance, California on October 20, 2017. Operation Jungle Book, a law enforcement initiative led by the US Fish and Wildlife Service that targeted wildlife smuggling, resulting in federal criminal charges against defendants who allegedly participated in the illegal importation and/ or transportation of numerous animal species – including a tiger, monitor lizards, cobras, Asian “lucky” fish, exotic songbirds and several coral species. (Photo by Mark Ralston/AFP Photo)

Giving out with a yell, Elke Sommer is tossed on the trampoline as she trains for her movie role as an athlete, on the playing field of the University of California at Los Angeles, June 8, 1967. (Photo by AP Photo)

Tactics reminiscent of the early American frontier days are now being used in Vietnam. Lieutenant Commander Donald D. Sheppard, UBN, of Coronado, California, aims a flaming arrow at a bamboo hut concealing a fortified Viet Cong bunker on the banks of the Bassac River, Vietnam on December 8, 1967. (Photo by AP Photo)

A woman reacts with flour over her face while playing a game with cake-making ingredients as part of local festivities marking Myanmar's 70th Independence Day in Yangon on January 4, 2018. The country is celebrating the 70th anniversary of its declaration of independence from British colonial rule. (Photo by Ye Aung Thu/AFP Photo)

In this 2017 photo provided by Simon Pierce, Jonathan Green checks on a fin-mounted satellite tag on a whale shark in the Galapagos Islands area of Ecuador. Despite typically being bigger than a double-decker bus, the elusive whale shark has only tiny, almost useless teeth. It's also one of the least understood animals in the ocean. (Photo by Simonjpierce.com via AP Photo)

Female Iraqi Kurdish peshmerga fighters watch on as they release a bear into the wild in the Gara Mountains near the northern Iraqi city of Dohuk on March 4, 2018, after Iraqi Kurdish Animal rights activists from a local NGO rescued it from a private home. (Photo by Safin Hamed/AFP Photo)

A boy plays with pelicans in Yoff, commune of Dakar, Senegal March 14, 2018. (Photo by Zohra Bensemra/Reuters)