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)

October winner. “A burst of the aurora borealis over Kirkjufell, taken in September 2016. This shot has been a holy grail for me and was finally captured after many trips”. MICK RYAN, JUDGE: Iceland is a hotspot for aurora photography and this composition of the symmetric, free-standing Kirkjufell and the trident waterfall is much-sought after. If you can time your visit when the aurora “kp” index is high and know the settings for nighttime aurora images, you may end up with a beautiful photograph like this. (Photo by DВ/The Guardian)

Staff of a boat restaurant on the Taedong River line up at the entrance as they wait to greet customers Sunday, June 18, 2017, in Pyongyang, North Korea. The boat is berthed along the river, which is the fifth longest river on the Korean Peninsula and runs through the country's capital, Pyongyang. (Photo by Wong Maye-E/AP Photo)

A team of female swimmers wearing facekini pose on beach by the sea on August 18, 2020 in Qingdao, Shandong Province of China. (Photo by Qian Han/VCG via Getty Images)

People pose near a new Banksy artwork in Rothesay Avenue, Nottingham, Britain on October 17, 2020. (Photo by Carl Recine/Reuters)

A stag reacts as magpies and crows fuss over a resting stag as they feed on ticks from the fur of the deer herd roaming on the Ashton Court Estate, Bristol, in crisp and cold Autumnal weather on November 23, 2020. (Photo by Ben Birchall/PA Images via Getty Images)

A couple watch the sunrise in front of the Mediterranean Sea in Barcelona, Spain, Sunday, January 24, 2021. (Photo by Emilio Morenatti/AP Photo)