An infrared portrait from NASA's Spitzer Space Telescope which shows generations of stars is seen in this undated NASA handout image released February 14, 2013. In this wispy star-forming region, called W5, the oldest stars can be seen as blue dots in the centers of the two hollow cavities (other blue dots are background and foreground stars not associated with the region). Red shows heated dust that pervades the region's cavities, while green highlights dense clouds. (Photo by NASA/Reuters/JPL-Caltech/Harvard-Smithsonian/Handout)

A three-month-old Sumatran tiger cub named “Bandar” shows his displeasure after being dunked in the tiger exhibit moat for a swim reliability test at the National Zoo in Washington, on November 6, 2013. All cubs born at the zoo must take a swim test before being allowed to roam in the exhibit. Bandar passed his test. (Photo by Manuel Balce Ceneta/Associated Press)

Characters dressed as Elmo and Cookie Monster who pose for tips take a photo by request from a tourist (2nd R, black pants) in Times Square in the Manhattan borough of New York City, January 29, 2016. (Photo by Rickey Rogers/Reuters)

In this Friday, March 3, 2017 photo, a ribbon on a staff member's outfit blows in the breeze as she arrives for the opening session of the Chinese People's Political Consultative Congress (CPPCC) at the Great Hall of the People in Beijing. The annual session of China's ceremonial legislature is designed to awe onlookers with its size and sweep, yet the experience is also made up of tiny moments, details that point to the personalities of the participants and the event's unique, sometimes quirky, traits that a casual observer might easily miss. (Photo by Mark Schiefelbein/AP Photo)

Chloe Lewis attends “The Ony Way Is Essex” season finale filming in Wintney, Hook, England on October 29, 2017. (Photo by Beretta/Sims/Rex Features/Shutterstock)

Nature, singles winner: Frogs with their legs severed struggle to the surface, surrounded by frogspawn, after being thrown back into the water in Covasna, Romania. (Photo by Bence Mate/World Press Photo 2019)

A baby sloth uses his mother as a hammock while she feasts on papayas in Heredia province in Costa Rica in April 2023. (Photo by William Steele/Solent News)

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)