From a gorilla tenderly embracing its caretaker to a black grouse's sensational mating ritual, this year's BigPicture: Natural World Photography Competition-winning images represent the best nature photography around the world.

Rarely-seen animal behaviour and extraordinary moments in nature are seen in this year's competition. Over 6500 submissions were entered by world-class photographers from 67 countries with the goal to showcase Earth’s biodiversity, as well as some of the mounting threats to the natural world. This year's grand prize-winning image was captured by photographer Audun Rikardsen of Tromsø, Norway. The jaw-dropping image captures a puffed-up black male grouse putting on a showy display to capture the attention of a female.

Rikardsen spent three years preparing for the shot, titled "Taking Centre Stage," which is actually the result of a happy coincidence. His original goal was to photograph majestic golden eagles but the black grouse frequently returned to Rikardsen's photography spot over the years and eventually became comfortable in front of the camera.

"This year's grand prize-winner is a stunning photo that combines technical skills and creative brilliance," Suzi Eszterhas, BigPicture jury chair, said in a statement. "Here, the photographer has managed to capture the grouse’s breeding display in a way that transports the viewer to the scene. It is a testament to how patience, dedication, and deeply knowing your subject can produce a remarkable image."

The competition was divided into a number of categories which include, Terrestrial Wildlife, Winged Life, Landscapes, Waterscapes & Flora, Aquatic Life, Art of Nature, and Human/Nature. The winner of the Human/Nature category was photographer James Gifford for an incredibly tender shot captured at Senkwekwe Gorilla Orphanage in Virunga National Park in the Democratic Republic of Congo where head caretaker André Bauma risks his life daily to look after the animals.

"While I was watching from a distance, one of André's charges enveloped him in a hug, giving me the chance to capture their remarkable relationship," Gifford said of the photo. "I have never before witnessed such a close and natural bond between any wildlife species and a human."

The winner of the terrestrial wildlife category was Mikhail Korostelev for this underwater photograph of a massive brown bear fishing for salmon in the South Kamchatka Sanctuary in Russia. While the winner of the winged life category was Piotr Naskrecki for his intricate shot of small winged carpenter ants on a bed of discarded wings taken in Gorongosa National Park in Mozambique.

All 50 winning images will be featured in the annual BigPicture photography exhibit, set to open on 26 July, 2019 at the California Academy of Sciences in San Francisco. A gallery of this year’s winning images was just published by bioGraphic, the Academy’s online magazine about science and sustainability.