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)

Team GB Rhythmic Gymnast Lynne Karina Hutchison during a training session on the seafront in Hove, following the outbreak of the coronavirus disease (COVID-19), Hove, Britain, June 10, 2020. (Photo by Peter Cziborra/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)

Pals let their hair down for one last hoorah in Cardiff, capital of Wales on September 12, 2020. Groups of friends crammed into pubs and restaurants to “go out in style” before the “rule of six” is enforced on Monday. (Photo by Huw Evans Picture Agency/The Sun)

An Extinction Rebellion protestor holds up a sign saying “You Can Change Climate Change” in St Martin's Lane in London, United Kingdom on August 23, 2021. (Photo by James Veysey/Rex Features/Shutterstock)

Bullet the bulldog skateboards in a seafront area in the city of Vladivostok, on Russia's Pacific coast on August 9, 2021. The 6-year-old dog learnt how to skateboard two years ago thanks to his owner, Sergei Shukshuyev. (Photo by Yuri Smityuk/TASS)

A leopard attacks a forest guard at Prakash Nagar village near Salugara on the outskirts of Siliguri on July 19, 2011. Six people were mauled by the leopard after the feline strayed into the village area before it was caught by forestry department officials. Forest officials made several attempt to tranquilised the full grown leopard that was wandering through a part of the densely populated city when curious crowds startled the animal, a wildlife official said. (Photo by Diptendu Dutta/AFP Photo)

Ana Mendez Casteñeda smokes marijuana during “Fumaton 420” outside the national Senate in Mexico City, Tuesday, April 20, 2021. The demonstrators are calling for the legalization of marijuana. (Photo by Marco Ugarte/AP Photo)