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 participant Saint Nicholas parade walks from house to house dressed in the traditional devil and Nicholas costumes in Francova Lhota district of Zlin, Czech Republic on December 3, 2017. This type of parade is one of the most popular age old tradition in a few villages in Wallachia region (eastern part of Czech Republic). Saint Nicholas walks the streets going from house to house three days and Saint Nicholas gives sweets to children and the devils get up to mischief. (Photo by Lukas Kabon/Anadolu Agency/Getty Images)

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)

Rev. Yeon Ah Lee Moon of the Sanctuary Church holds a gold AR-15 during a ceremony to rededicate marriages at the World Peace and Unification Sanctuary in Newfoundland, Pennsylvania, USA, 28 February 2018. The church, a breakaway from the Unification Church, believes guns are a symbol of the “rod of iron” referenced in the Book of Revelations. (Photo by Jim Lo Scalzo/EPA/EFE)

Most Russians intending to vote for Vladimir Putin in Sunday's election say stability is at the root of their faith in their candidate – though many young voters believe it's time for a change of leader. Putin, 65, is expected to win a fourth term in office with 69 percent of the vote, according to the latest survey by a state-run pollster. Reuters correspondents and photographers who travelled around the country talking to voters ahead of the March 18 election found nothing to contradict expectation of an emphatic Putin victory. (Photo by Anton Vaganov/Reuters)

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)

Kang Na-ra, a North Korean defector who is now a beauty YouTuber, points at her lips after putting on a lipstick made by North Korea, in Seoul, South Korea, June 11, 2019. (Photo by Kim Hong-Ji/Reuters)