A mahout watches the Thai animation movie Kan Kluay with his elephant in Ayuthaya province, about 80km (49 miles) north of Bangkok June 5, 2006. The movie tells the story of a young Thai wild elephant who, while looking for his father, becomes the war elephant of the Thai King fighting against Burma and restored Thailand's ancient Ayuthaya empire that existed about 400 years ago. (Photo by Sukree Sukplang/Reuters)

Frances Fowler leads the Bowie VFD Marching Thoroughbreds in the Bowie 4th of July Parade in Bowie, Md., on July 4, 1976. (Photo by James M. Thresher/The Washington Post via Getty Images)

Winner of the National Park Foundation's photo contest; Honorable Mention: Fan Favorite. Grand Canyon National Park, Arizona. Three friends enjoy sunrise over the Grand Canyon. (Photo by Peter Blanchard)

The Sphinx breed of cat “Adam vom Feisastern” of the German breeder Sabine Braeuer waits on a jury table during an annual International Pedigree Dog and Cat Show in Erfurt, Germany on June 10, 2012. (Photo by Jens Meyer/Associated Press)

A Miniature Dachshund (L) wears a duck bill-shaped dog muzzle while sitting in a stroller with another Miniature Dachshund at the “Interpets” international pet fair in Tokyo, Japan, April 2, 2015. (Photo by Kiyoshi Ota/EPA)

A Hawaiian cleaner wrasse provides its cleaning services to a yellowfin goatfish in a reef community off the Big Island in Hawaii. Cleaner species help rid their hosts of ectoparasites, dead tissue, bacteria and fungi. Studies have shown cleaning to play a vital role in keeping many reef ecosystems healthy. (Photo by Marty Snyderman/Caters News Agency)

The Invasion. A quiet street in Macau. Modernization around is quickly changing the city, as documented by Paul Tsui. (Photo by Paul Tsui/National Geographic Travel Photographer of the Year Contest)

The fourth annual BigPicture Natural World Photography Competition aims to celebrate the diversity of life on Earth, and encourages people to protect and conserve it. Here: “The Salmon Catchers”. Terrestrial Wildlife. To capture this view of a mother grizzly bear and her cub, photographer Peter Mather set up a camera trap on a log that he knew the bears tended to traverse while fishing for salmon, in the Yukon River watershed in Canada. (Photo by Peter Mather/BigPicture Natural World Photography Competition 2017)