A vintage car sits in flood water on March 20, 2019 in Hamburg, Iowa. Although flood water in the town has started to recede many homes and businesses remain surrounded by water. Several Midwest states are battling some of the worst flooding they have experienced in decades as rain and snow melt from the recent “bomb cyclone” has inundated rivers and streams. At least three deaths have been linked to the flooding. (Photo by Scott Olson/Getty Images)

A family take a souvenir picture next to giant male panda Xiao Liwu, who was born at the San Diego Zoo and will be repatriated to China with his mother Bai Yun, bringing an end to a 23-year-long panda research program in San Diego, California, U.S., April 18, 2019. (Photo by Mike Blake/Reuters)

A supporter dressed as flamingo cheers on the riders during the 12th stage of the 102nd Giro d'Italia – Tour of Italy – cycle race, 158kms from Cuneo to Pinerolo on May 23, 2019. (Photo by Marco Bertorello/AFP Photo)

A woman holds up what the Chris Steaks & Burgers restaurant says is Thailand's biggest burger weighing more than 6 kilograms, before a competition held to eat it at the restaurant in Bangkok, Thailand, October 11, 2019. Chris Steaks and Burgers is offering a 10,000 baht ($330) prize for anyone who can finish the mammoth snack in nine minutes – one baht for every calorie. (Photo by Jiraporn Kuhakan/Reuters)

Female Iraqi Kurdish peshmerga fighters watch on as they release a bear into the wild in the Gara Mountains near the northern Iraqi city of Dohuk on March 4, 2018, after Iraqi Kurdish Animal rights activists from a local NGO rescued it from a private home. (Photo by Safin Hamed/AFP Photo)

Members of the Mayossa folk dance group pour water on a young woman in Kiskunmajsa, Hungary on April 2, 2018. According to an old Hungarian tradition, celebrated for several hundred years, young men pour water on young women, who in exchange present their sprinklers with beautifully colored eggs on Easter Monday. (Photo by Sandor Ujvari/EPA/EFE/Rex Features/Shutterstock)

In this Thursday, May 25, 2017 photo, Donte, a musician who only gave his first name, straightens out dollar bills on his first day in a brand new Chewbacca costume purchased from eBay for $441, in the Hollywood section of Los Angeles. Donte said he replaced the old one because he wasn't making any money with it. (Photo by Jae C. Hong/AP Photo)

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)