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)

Wakodahatchee wetlands, Delray Beach, Florida, US. Equipped with sinewy necks and spear-like bills, great blue herons can lunge with fearsome speed to strike their aquatic prey. Adults will also employ rapid stabbing motions as one aspect of their complex courtship displays; they’re seemingly dangerous moves, but fitting to the intensity of mating season. (Photo by Melissa Rowell/Audubon Photography Awards)

Girls dressed in “Hanfu”, or Han clothing, prepare for an event to mark the traditional Qixi festival, the Chinese equivalent of Valentine's Day, at a park in Beijing, China, August 7, 2019. Chinese for “Han clothing”, “Hanfu” is based on the idea of donning costumes worn in bygone eras by China's dominant Han ethnicity. Some of the most popular styles are from the Ming, Song and Tang dynasties. Hanfu enthusiasts doubled to two million in 2018 from a year earlier, according to a survey by Hanfu Zixun, a popular community account on the Wechat social media platform. (Photo by Jason Lee/Reuters)

July gestures next to her boyfriend Jason Schaller while they are suspended from hooks pierced through their skins by professional body artist Wei Yilaien at a bar in Shanghai, China September 16, 2018. “I like being unique and I don't like doing things that many people are aware of and would accept”, said Wei, 24, who staged the show of extreme body piercing in China's normally buttoned down financial capital. (Photo by Aly Song/Reuters)

Behaviour winner; Courting Royals: two royal terns in courtship display by Kristian Bell. Another beautiful morning on a beautiful beach on the Gulf Coast of Florida seemed to prompt these two royal terns to commence an intricate courtship dance. The photograph was taken with a Canon 300mm lens and 2x extender. (Photo by Kristian Bell/Deakin University/Royal Society Publishing Photography Competition 2018)

David Goffin of Belgium meets a koala during a promotional event for the Australian Open tennis tournament at Melbourne Park on January 17, 2018. (Photo by Fiona Hamilton/Reuters/Tennis Australia)

A passenger (L) gets inside a decorated matatu as other passengers wait for it to fill at night in the streets of Nairobi, Kenya, 24 March 2018. The Matatu culture is very big in Kenya, the minibuses are decorated with colorful graffiti inside and outside and most of them are equipped with TV screens, high-speed internet, and power sockets. (Photo by Daniel Irungu/EPA/EFE)

A bloodied man who carried dead and wounded, speaks on the phone at the site of a suicide attack an explosion that struck a protest march, in Kabul, Afghanistan, Saturday, July 23, 2016. Witnesses in Kabul say that an explosion causing multiple casualties struck the march by members of Afghanistan’s largely Shiite Hazara ethnic minority group, who were demanding that a major regional electric power line be routed through their impoverished home province. (Photo by Omar Sobhani/Reuters)