A great tit eats food from the top of a photographer's hat as the press wait for politicians on Downing Street on December 16, 2019 in London, England. The UK's Prime Minister is set to hold a mini Cabinet reshuffle to replace outgoing ministers following last week's general election victory. (Photo by Leon Neal/Getty Images)

A streaker races across the field and is caught by security during the Super Rugby match between New Zealand's Highlanders and South Africa's Sharks at Forsyth Barr Stadium in Dunedin on February 7, 2020. (Photo by Marty Melville/AFP Photo)

A medical worker in protective gear sprays mist on her colleague during a hot day at an outdoor clinic for coronavirus tests at a public health facility in the southwestern city of Gwangju, South Korea, 05 June 2020. (Photo by Yonhap/EPA/EFE)

An art wall painting representing performance artist Marina Abramovic by Italian artist Maurizio Cattellan to publicize his upcoming exhibition The Artist is Present, in Shanghai, China, is displayed on a facade of a building, in Milan, Italy, Wednesday, September 19, 2018. (Photo by Luca Bruno/AP Photo)

An Oriental Garden Lizard sits on a tree in Gauhati, India, Tuesday, April 16, 2019. During the breeding season, the male lizard's head and throat turn a bright color. (Photo by Anupam Nath/AP Photo)

A demonstrator uses a slingshot during a protest against Chile's government in Santiago, Chile, November 14, 2019. (Photo by Jorge Silva/Reuters)

Women members of the national police take part in a parade during a graduation ceremony in Bogota, Colombia on November 7, 2019. (Photo by Juan Barreto/AFP Photo)

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)