In this February 28, 2015 photo, teammates struggle to lift a bull off the trapped leg of a charro, during the bull riding event at a charreada in Mexico City. National Charros Association President Manuel Basurto Rojas said: “We in charreria are taking things into our own hands. We have codes, we have rules, for how to treat the animals. On the other hand, there is a lot of danger involved for the men doing these tricks”. (Photo by Rebecca Blackwell/AP Photo)

A dog catches a wave during the Surf City Surf Dog Contest in Huntington Beach, California September 27, 2015. (Photo by Lucy Nicholson/Reuters)

A model wears a creation by Taiwanese fashion house Shiatzy Chen as part of its Spring-Summer 2016 ready-to-wear fashion collection, presented during the Paris Fashion Week in Paris, France, Tuesday, October 6, 2015. (Photo by Jerome Delay/AP Photo)

Children of local herders gather at a reindeer camping ground, some 200 km (124 miles) northeast of Naryan-Mar, the administrative centre of Nenets Autonomous Area, far northern Russia, August 2, 2015. People, including local herders and members of their families, gathered at the site to mark Reindeer Day, a professional holiday of reindeer breeding workers, which is celebrated annually on August 2 in the region. (Photo by Sergei Karpukhin/Reuters)

16-year-old panda, Ye Ye, rests in an enclosure at the Wolong Nature Reserve, a conservation center that trains pandas for release into the wild. This image was published in the August 2016 National Geographic magazine as part of the “Pandas Gone Wild” story. (Photo by Ami Vitale/National Geographic Creative)

Model Sara Sampaio shows some side boob as she arrives at Balmain Fashion Show during Paris Fashion Week in Paris, France on September 28, 2017. (Photo by Splash News and Pictures)

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)