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)

Children enjoy a sledge ride past ice swimming fans at the Zalew Zegrzynski lake in Nieporet, Poland, Sunday, February 25, 2018. A cold wave hit Poland with the temperature minus 8 degree Celsius (17.6 Fahrenheit) during the day and dropping to minus 16 degree Celsius (3.2 Fahrenheit) in the night in central Poland. (Photo by Alik Keplicz/AP Photo)

Performers ride atop a car leading to the the National Circus Day celebration in Santiago, Chile, Saturday, September 4, 2021, amid the new coronavirus pandemic. Chile's Culture Minister set the stage for the first circus performances with a ringside public since the beginning of the pandemic quarantine measures as the South American country looks to fully roll back almost all COVID-19 related restrictions. (Photo by Esteban Felix/AP Photo)

In this May 2016 photo released by The Ocean Agency/XL Catlin Seaview Survey, a boat sails near a coral reef that has been bleached white by heat stress in the Maldives. oral reefs, unique underwater ecosystems that sustain a quarter of the world's marine species and half a billion people, are dying on an unprecedented scale. Scientists are racing to prevent a complete wipeout within decades. (Photo by The Ocean Agency/XL Catlin Seaview Survey via AP Photo)

A Maori warrior prepares to challenge Prince Charles during his welcome to Takanhanga Marae in Kaikoura, New Zealand November 23, 2019. (Photo by Tracey Nearmy/Reuters)

A view shows “The Farnese Bridge”, a participatory monumental cardboard installation by French artist Olivier Grossetete, over the Tiber river in front of the Palazzo Farnese, the seat of the French embassy in Italy, during its inauguration in Rome on July 13, 2021. A French Embassy project, the Farnese bridge is the realization of the dream of Cardinal Farnese, who wished to build a bridge over the Tiber to connect Palazzo Farnese to the gardens of the Villa Farnesina. A project, at the time, entrusted to Michelangelo, but that remained unfinished. (Photo by Filippo Monteforte/AFP Photo)

Penny Verdin displays a sleeping squirrel she helped rescue after it was injured during Hurricane Ida, Saturday, September 4, 2021, in Dulac, La. (Photo by John Locher/AP Photo)

A priest comforts one of the relatives of the victims, before a mass in their memory, as Lebanon marks one-year anniversary of Beirut port explosion, at the port in Beirut, Lebanon on August 4, 2021. United in grief and anger, families of the victims and other Lebanese came out into the streets of Beirut on Wednesday to demand accountability as banks, businesses and government offices shuttered to mark one year since the horrific explosion. (Photo by Aziz Taher/Reuters)