An Amur tiger walks across a passageway after a news conference at the Philadelphia Zoo, Wednesday, May 7, 2014, in Philadelphia. The see-through mesh pathway called Big Cat Crossing is part of a national trend called animal rotation that zoos use to enrich the experience of both creatures and guests. (Photo by Matt Slocum/AP Photo)

Strokkur geyser against cloudy sky at sunset. Strokkur is a fountain geyser located in a geothermal area beside the Hvítá River in Iceland in the southwest part of the country, east of Reykjavík. It is one of Iceland's most famous geysers, erupting once every 6–10 minutes. Its usual height is 15–20 m, although it can sometimes erupt up to 40 m high. (Photo by Teatsche Dijkhuis/Getty Images/EyeEm)

Youth category winner: Symphony No 5 by Giacomo Redaelli (Italy). (Photo by Giacomo Redaelli/2019 Nature Photographer of the Year)

A motorcycle sits at the site of a destroyed home after the Soberanes Fire burned through the Palo Colorado area, north of Big Sur, California, July 31, 2016. (Photo by Michael Fiala/Reuters)

Khan, a five-year-old male White Bengal tiger, looks on inside an open-air cage at the Royev Ruchey zoo in Krasnoyarsk, Russia, October 21, 2016. (Photo by Ilya Naymushin/Reuters)

A woman rides a horse through the biannual Stow Horse Fair in the town of Stow-on-the-Wold, southern England on October 24, 2019. The Stow Horse Fair has attracted Gypsy and Traveller people from all over the country to the Cotswold town every May and October since 1476. (Photo by Oli Scarff/AFP Photo)

National Geographic photographer Steve Winter has spent most of his adult life shooting wild cats. Photo: A 14-month-old cub, cooling off in a pond, is riveted by a deer that appeared near the shore. Tigers are powerful swimmers; they can easily cross rivers four to five miles wide and have been known to swim distances of up to 18 miles. (Photo by Steve Winter/National Geographic)