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 woman is helped out of the wrecked car of a train that derailed at the station of Pioltello Limito, on the outskirts of Milan, Italy, Thursday, January 25, 2018. Italian officials said that the commuter train derailed in northern Italy, killing some people, seriously injuring 10 and trapping others heading into Milan at the start of the work day. (Photo by AP Photo/Stringer)

Even upside down, a stereophonic turntable continues to play and hold the interest of Helen Sorowitz, a visitor to the New York High Fidelity Show in New York, September 9, 1960. (Photo by Ruben Goldberg/AP Photo)

Women dancing at the disco club Xenon in New York City, USA in 1978. Xenon was a popular disco in Manhattan in the late 1970s and early 1980s. It was the only nightclub popular enough to compete with Studio 54. (Photo by Waring Abbott/Getty Images)

A hint of Spring Fever is evidenced by this passerby tipping his hat to a store fixture mannequin on a State St. sidewalk in downtown Chicago on March 23, 1978. The mannequin was awaiting pickup to be transported. (Photo by AP Photo)

Members of the Mayossa folk dance group pour water on a young woman in Kiskunmajsa, Hungary on April 2, 2018. According to an old Hungarian tradition, celebrated for several hundred years, young men pour water on young women, who in exchange present their sprinklers with beautifully colored eggs on Easter Monday. (Photo by Sandor Ujvari/EPA/EFE/Rex Features/Shutterstock)

A model slips on the runway while parading an outfit by Australian designer Toni Maticevski at Fashion Week Australia in Sydney on May 15, 2016. (Photo by William West/AFP Photo)

A picture made available 26 April 2016 shows a tiger playing in the water with a trainer nicknamed “Super Tiger Man” at the Tiger Temple in Kanchanaburi province, Thailand, 24 April 2016. The site known in Thai as “Wat Pa Luangta Maha Bua Yannasampanno” has been the focus of a dispute with the Department of National Parks, Wildlife and Plant Conservation (DNP) after the DNP asked in 2015 that the temple hands over its 147 tigers since it was not licensed to keep them. The temple has requested for a zoo license according to its managing director. (Photo by Diego Azubel/EPA)