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)

Iraqi teenagers swim in waste water from the nearby Tuweitha nuclear facility near Baghdad, Iraq on May 28, 2003. Iraqis are consuming contaminated water unaware of the dangerous pollutants that can cause severe ill health. (Photo by Damir Sagolj/Reuters)

Sukhoi Su-30SM jet fighters of the Sokoly Rossii (Falcons of Russia) aerobatic team fly in formation during the International Army Games 2016, in Dubrovichi outside Ryazan, Russia, August 5, 2016. (Photo by Maxim Shemetov/Reuters)

Supporters enjoy the atmosphere before watching England's second World Cup match against USA on the big screen at Road to Victory, Europe's largest World Cup fan park at Mayfield Depot on November 25, 2022 in Manchester, England. The English team came into their second World Cup 2022 match favoured to win. (Photo by Anthony Devlin/Getty Images)

A woman dressed in Ukrainian national costume poses for a photograph in front destroyed Russian military equipment at Khreshchatyk street in Kyiv on August 20, 2022, that has been turned into an open-air military museum ahead of Ukraine's Independence Day on August 24, amid Russia's invasion of Ukraine. (Photo by Dimitar Dilkoff/AFP Photo)

Garbage, including plastic waste, is seen at the beach of Costa del Este, in Panama City, on April 19, 2021. Every two weeks, Marine Biology students descend about five meters in the sea to take care of a coral nursery of the staghorn species (Acropora cervicornis) in Portobelo, Panama, with which they aim to restore reefs damaged by climate change and pollution, as part of the Reef2Reef project. (Photo by Luis Acosta/AFP Photo)

A woman dressed as the Wizard of Oz’s Dorothy walks her dog dressed as the Cowardly Lion as they attend the annual Congressional Dog Costume Parade on Capitol Hill in Washington, DC, on October 27, 2021. (Photo by Jim Watson/AFP Photo)

Vendors warm themselves as they light a bonfire at a market during a nationwide power outage, in Muzaffarabad on January 23, 2023. A massive power breakdown in Pakistan on January 23 affected most of the country's more than 220 million people, including in the mega cities of Karachi and Lahore. (Photo by Sajjad Qayyum/AFP Photo)