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)

Stingray City is a series of shallow sandbars found in the North Sound of Grand Cayman, Cayman Islands. It is a tourist attraction, where southern stingrays are found in abundance and visitors can pet and interact with the animals.

Jack, a Lurcher from Dogs Trust Salisbury, walks past a window display of models in a Dogs Trust shop window in Salisbury, as part of a campaign to discourage the impulse buying of dogs ahead of Valentine's Day, on February 10, 2014. (Photo by Matt Alexander/PA Wire)

Sergeant Andrew Garrett watches K-Dog, a bottlenose dolphin attached to Commander Task Unit 55.4.3, leap out of the water while training near the USS Gunston Hall March 18, 2003 in the Persian Gulf. (Photo by U.S. Navy/Getty Images)

A sеx worker participates in a march to raise public awareness on human rights issues in their profession on International Day to End Violence Against Sеx Workers in Skopje, Macedonia December 17, 2016. (Photo by Ognen Teofilovski/Reuters)

A woman takes a photograph of a sculpture titled “Couple Under an Umbrella, 2013” by Australian sculptor Ron Mueck during a preview of his exhibition at the Pinacoteca Museum in Sao Paulo November 19, 2014. (Photo by Nacho Doce/Reuters)

Horses compete in the VEA, VHBPA, and VTA Maiden Claiming Hurdle race during the Virginia Gold Cup Races at Great Meadow on Saturday May 06, 2023 in The Plains, VA. (Photo by Matt McClain/The Washington Post)

Scarlett points at the huge ice sculpture of a bear during a Photocall for Magical Ice Kingdom at Hyde Park Winter Wonderland at Hyde Park on November 17, 2016 in London, England. It is the event's 10th anniversary this year. (Photo by Ben Perry/Getty Images)