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)

The front wheels of a tractor, pulling a trailer overloaded with sugarcane, are seen lifted off the ground as it passes through the streets of Karor Lan Esan, Pakistan December 6, 2015. (Photo by Caren Firouz/Reuters)

Brazilian bikinis are displayed outside a shop near Copacabana beach in Rio de Janeiro on August 4, 2016 on the eve of the opening of the Rio 2016 Olympic Games. (Photo by Leon Neal/AFP Photo)

Daniel Cheong, a dog behaviorist and trainer, steps over a leash as he walks a pack of dogs in Arlington, Va. on November 13, 2018. (Photo by Ricky Carioti/The Washington Post)

A protester gestures as he holds a dog before a burning barricade during protests in Harare, Zimbabwe on January 15, 2019. (Photo by Philimon Bulawayo/Reuters)

A worker stack bricks on his head at a brick factory in Lalitpur January 12, 2015. (Photo by Navesh Chitrakar/Reuters)

Palestinians inspect a destroyed street after an Israeli strike in Gaza City, 13 May 2021. In response to days of violent confrontations between Israeli security forces and Palestinians in Jerusalem, various Palestinian militants factions in Gaza launched rocket attacks since 10 May that killed at least six Israelis to date. Gaza Strip's health ministry said that at least 65 Palestinians, including 13 children, were killed in the recent retaliatory Israeli airstrikes. Hamas confirmed the death of Bassem Issa, its Gaza City commander, during an airstrike. (Photo by Mohammed Saber/EPA/EFE)

Firls attend Sunday Mass at Sacre-Coeur church, in Port-au-Prince, Sunday, July 11, 2021, four days after President Jovenel Moise was assassinated in his home. (Photo by Joseph Odelyn/AP Photo)