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)

An exhausted Rohingya refugee woman touches the shore after crossing the Bangladesh-Myanmar border by boat through the Bay of Bengal, in Shah Porir Dwip, Bangladesh, September 11, 2017. (Photo by Danish Siddiqui/Reuters)

The Aurora Borealis (Northern Lights) lights up the sky near the village of Pallas (Muonio region) of Lapland, Finland September 8, 2017. (Photo by Alexander Kuznetsov/Reuters/All About Lapland)

Yi Arias, a CORE crew member in an upbeat mood at COVID-19 mass-vaccination of healthcare workers taking place at Dodger Stadium in Los Angeles, California, U.S., January 15, 2021 (Photo by Irfan Khan/Pool via Reuters)

A woman participates in a ritual for the African sea goddess Yemanja at Ramirez Beach in Montevideo, Uruguay, Tuesday, February 2, 2021. (Photo by Matilde Campodonico/AP 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)

Models display creations by fashion house Andres Sarda during the Mercedes Benz Fashion Week, amid the coronavirus disease (COVID-19) outbreak in Madrid, Spain, April 8, 2021. (Photo by Sergio Perez/Reuters)

April Haze, a San Jose-based stripper, teaches a pole dance class to her students at Revel Room Studios in Milpitas, California, April 15, 2021. As some of the United States' estimated 3,821 strip clubs start to open up again, women who work as strippers are confronting a transformed industry. Revenue in the industry is estimated to have decreased 17.4% in 2020 and is forecast to fall another 1.5% this year, according to research by IBISWorld. (Photo by Brittany Hosea-Small/Reuters)