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)

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)

In this February 19, 2017 photo, a couple dances during the “If you don't give me....then you lend me” Carnival street party on Ipanema beach, in Rio de Janeiro, Brazil. The typical view of Carnival in Brazil is anything goes, with no headdress too big, no outfit too small, no song too ribald, but this year some organizers of the world's best known party are drawing the line at lyrics that are sexist, homophobic or racist. (Photo by Silvia Izquierdo/AP Photo)

A family of refugees shelters under a truck carrying plastic lota, kettles used to perform Muslim ablutions in Muna Garage, Maiduguri, Nigeria February 16, 2017. (Photo by Paul Carsten/Reuters)

Two horses appear to burst into laughter before a sweet embrace. The horses both turn their head to look at the camera and flash their teeth, treating the lucky photographer to a rare shot. Moments later the pair show their affectionate side by coming together and “hugging”. Photographer Nir Amos, 34, said he was “amazed” to capture the horses “laughing” in a field near Skógar, in the south east of Iceland on July 31, 2018. (Photo by Nir Amos/Solent News & Photo Agency)

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)

Migrant children play with leaves during Christmas Eve at a shelter, as they travel with their parents as part of a caravan with humanitarian visas to transit throughout the country, in Monterrey, Mexico on December 24, 2021. (Photo by Daniel Becerril/Reuters)

Cemetery workers lift a corpse from a coffin to a metal plate as they prepare the body for cremation at a cemetery in Maracaibo, Venezuela, November 27, 2019. Some overcome the financial burden of a relative's death by renting caskets, a cheaper option than buying one. (Photo by Rodrigo Abd/AP Photo)