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)

A young Bengal tiger cub smuggled into the US and seized at the Mexico border is displayed for the media during Operation Jungle Book at the US Fish and Wildlife Service in Torrance, California on October 20, 2017. Operation Jungle Book, a law enforcement initiative led by the US Fish and Wildlife Service that targeted wildlife smuggling, resulting in federal criminal charges against defendants who allegedly participated in the illegal importation and/ or transportation of numerous animal species – including a tiger, monitor lizards, cobras, Asian “lucky” fish, exotic songbirds and several coral species. (Photo by Mark Ralston/AFP Photo)

A Philippine Airlines A300 Airbus plane lies near the service road of a highway south of Manila after it overshot the runway, September 19, 1987 in Manila upon landing from Singapore. Nobody was injured among 135 passengers and crewmen on board. (Photo by Bullit Marquez/AP Photo)

In this 2017 photo provided by Simon Pierce, Jonathan Green checks on a fin-mounted satellite tag on a whale shark in the Galapagos Islands area of Ecuador. Despite typically being bigger than a double-decker bus, the elusive whale shark has only tiny, almost useless teeth. It's also one of the least understood animals in the ocean. (Photo by Simonjpierce.com via AP Photo)

Cambodian children sleep on a pavement at a park in Phnom Penh on July 8, 2016. (Photo by Tang Chhin Sothy/AFP Photo)

A boy jumps from a swing during sunset in Valras-Plage, southern France December 29, 2014. (Photo by Yves Herman/Reuters)

Storm erupts over Pacific Ocean as plane zooms past at 37,000 ft. The amazing picture shows a massive cloud erupting against a starry night sky as the off-duty airman Santiago Borja flew over the Pacific near Panama City. He had just moments to take the breathtaking snap as the Boeing 767 zoomed by at 37,000 ft on its way from North America to Ecuador. He also had take the picture perfectly in time with the flash of lightning to capture the storm in all its glory. (Photo by Santiago Borja/Solent News)

A mother bear takes a dip in the water to cool off in the warm summer sun but refuses to leave her three youngsters behind – so they climb aboard her back. (Photo by Jon Langeland/Solent News & Photo Agency)