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)

Tactics reminiscent of the early American frontier days are now being used in Vietnam. Lieutenant Commander Donald D. Sheppard, UBN, of Coronado, California, aims a flaming arrow at a bamboo hut concealing a fortified Viet Cong bunker on the banks of the Bassac River, Vietnam on December 8, 1967. (Photo by AP Photo)

A woman reacts with flour over her face while playing a game with cake-making ingredients as part of local festivities marking Myanmar's 70th Independence Day in Yangon on January 4, 2018. The country is celebrating the 70th anniversary of its declaration of independence from British colonial rule. (Photo by Ye Aung Thu/AFP Photo)

A man wears a busho mask and a costume made of sheep pelt while climbing up a ladder outside a barn in Mohacs, Hungary, 20 February 2020, on the first day of carnival. The traditional Busho carnival, which marks the end of winter, dates back to the 16th century. According to local legend, members of an ethnic South Slavic group living in Mohacs at the time dressed up in similar costumes and wore wooden masks to scare away Ottoman invaders, who mistook them for demons. (Photo by Tamas Soki/EPA/EFE)

A resident (unseen) uses a belt to get vegetables in Wuhan, in China's central Hubei province on March 13, 2020. China reported just eight cases of the coronavirus on March 13, with no new domestic infections outside the epicentre of Hubei province. (Photo by AFP Photo/China Stringer Network)

The clown is on tour at Outlets on June 7, 2020 in Wuhan,Hubei Province,China.Wuhan has seen its urban life gradually get back to normal following encouragement from local city management to open up street-stalls. Since January, China has recorded more than 81,000 cases of COVID-19 and at least 3200 deaths, mostly in and around the city of Wuhan, in central Hubei province, where the outbreak first started. (Photo by Getty Images/Stringer)

A bride to be in the Grassmarket in Edinburgh, Scotland on Monday, April 26, 2021, as beer gardens, non-essential shops, restaurants and cafes, along with swimming pools, libraries and museums in Scotland reopen today after lockdown restrictions have eased. (Photo by Andrew Milligan/PA Images via Getty Images)

Swan Uppers try to capture a swan and it's Cygnets on the River Thames near Windsor, England, during Swan Upping, with Windsor Castle in background, Tuesday July 20, 2021. The ancient tradition of Swan Upping is the annual census to gauge the numbers and health of the swan population on the River Thames. (Photo by Steve Parsons/PA Wire via AP Photo)