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)

Filipino children play as they are doing caroling activities on the street near an airport, days before Christmas in Manila, Philippines, 20 December 2017. Filipinos celebrate the longest Christmas in the world which starts as early as September every year. (Photo by Francis R. Malasig/EPA/EFE)

People react as a Canadian man wearing only a pair of shorts orders a drink from a fast food outlet in Gangneung Curling Centre on day 10 of the PyeongChang 2018 Winter Olympic Games on February 19, 2018 in Gangneung, South Korea. (Photo by Carl Court/Getty Images)

Children enjoy a sledge ride past ice swimming fans at the Zalew Zegrzynski lake in Nieporet, Poland, Sunday, February 25, 2018. A cold wave hit Poland with the temperature minus 8 degree Celsius (17.6 Fahrenheit) during the day and dropping to minus 16 degree Celsius (3.2 Fahrenheit) in the night in central Poland. (Photo by Alik Keplicz/AP Photo)

The Duchess of Cambridge pulls a pint with the Duke of Cambridge during their visit to Belfast Empire Hall for an informal party to celebrate inspirational young people who are making a real difference in Northern Ireland as part of their two day visit to Northern Ireland on February 27, 2019. (Photo by Aaron Chown/PA Wire Press Association)

An art wall painting representing performance artist Marina Abramovic by Italian artist Maurizio Cattellan to publicize his upcoming exhibition The Artist is Present, in Shanghai, China, is displayed on a facade of a building, in Milan, Italy, Wednesday, September 19, 2018. (Photo by Luca Bruno/AP Photo)

Olena Korzeniuk, a 15-year-old girl poses on the stairs during a bid to set the national record for the longest hair on a child in Kiev, Ukraine on March 12, 2019. During a ceremony, the experts of the National Register of Records found the blonde hair of the Ukrainian Rapunzel to be 2.35m (6.5ft) long. (Photo by Tarasov/Ukrinform/Barcroft Images)

Britain's Camilla, Duchess of Cornwall watches a performance during a salsa school visit in Havana, Cuba March 26, 2019. (Photo by Phil Noble/Reuters)