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)

People cling on to a crowded train as it leaves a railway station during the ongoing Coronavirus Disease (COVID-19) outbreak in Ghaziabad, India, September 21, 2021. (Photo by Anushree Fadnavis/Reuters)

Burning candles illuminate graves as a Bangladeshi man observes a contemplative moment on All Souls' Day at the Dhaka Christian Cemetery at Wari in Dhaka, Bangladesh, 02 November 2021. People on All Saints Day and All Souls Day pay respect to deceased relatives and loved ones by placing flowers on their tombs or maintaining their graves and lighting candles. (Photo by Monirul Alam/EPA/EFE)

A public bus makes its way on a flooded road after heavy monsoon rains in Mumbai, India on August 4, 2019. India receives its monsoon rains from June to September. (Photo by Indranil Mukherjee/AFP Photo)

Models wearing facekinis, popular with female bathers who want to protect more than just their modesty, pose for a picture on a beach on August 5, 2019 in the Chinese seaside city of Qingdao, Shandong Province of China. (Photo by Xu Chongde/VCG via Getty Images)

In this Friday, August 9, 2019, file photo, Pakistan Rangers soldiers face Indian Border Security Force soldiers at a daily closing ceremony on the Indian side of the Attari-Wagah border. India's recent clampdown has a long history in Kashmir and the conflict has existed since the late 1940s, when India and Pakistan won independence from the British empire and began fighting over rival claims to the Muslim-majority territory. India and Pakistan have fought two of their three subsequent wars over Kashmir, and each administers a portion of the region. India has long seen the Kashmiri struggle for self-determination as Islamabad's proxy war against New Delhi. (Photo by Prabhjot Gill/AP Photo/File)

Fans dressed up in costume await the cast members on the red carpet at the world premiere of the film "The Avengers: Endgame" in Los Angeles, California, April 22, 2019. (Photo by Mario Anzuoni/Reuters)

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)