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)

Frog legs it! Indonesian flying frog tries to hitch a ride on snail's back before realising it would be quicker to hop it alone. A tiny frog struck up an unlikely friendship with a giant African land snail after clambering onto its shell to catch a ride. (Photo by Hendy Mp/SOLENT/Visual Press Agency)

A man drinks at a "colored" water cooler in a streetcar terminal in Oklahoma City, July 1939. (Photo by Reuters/Library of Congress)

Members of the Bearded Ladies Cabaret cross Broad St., before a march by supporters of Sen. Bernie Sanders, I-Vt., in Philadelphia, on the first day of the Democratic National Convention, July 25, 2016. (Photo by Tom Williams/CQ Roll Call/AP Images)

Gold medalist Jesper Pedersen of Norway with silver medalist Rene de Silvestro of Italy and bronze medalist Liang Zilu of China are seen during the flower ceremony for the Para Alpine Skiing, Men's Giant Slalom Sitting on March 10, 2022. (Photo by Aly Song/Reuters)

Demonstrators react during a rally in support of legal and safe abortion and to mark the International Safe Abortion Day in Bogota, Colombia on September 28, 2021. (Photo by Luisa Gonzalez/Reuters)

Gold medalist Luiza Gega of Albania celebrates after the Athletics - Women's 3000m Steeplechase Final on day 10 of the European Championships Munich 2022 at Olympiapark on August 20, 2022 in Munich, Germany. (Photo by Wolfgang Rattay/Reuters)

Astronauts Harrison Schmitt (left) and Eugene Andrew Cernan practice taking geological samples at the Kennedy Space Center in Florida, in preparation for NASA's scheduled Apollo 17 lunar landing mission, on August 28, 1972. Schmitt is the Lunar Module Pilot and Cernan is the mission's Commander. They are training for their period of EVA (extravehicular activity) on the Moon. (Photo by Space Frontiers/Getty Images)