From a marine iguana foraging for algae to the harsh beauty of dry salt beds in Argentina, the highlights of the 2019 BigPicture: Natural World Photography Competition including bizarre and striking images.

There's the male black grouse (above) captured in Norway by Audun Rikardsen, for example, who had set up a blind to photograph a resident golden eagle. One day, the eagle was replaced by the grouse, who quickly got used to the camera and flash. Rikardsen says it was almost as if the proud bird enjoyed being in the spotlight, strutting his gorgeous plumage. Rikardsen's photo, "Taking Center Stage," was the 2019 Grand Prize winner.

Now in its sixth year, the annual competition encourages photographers to submit work that will both illustrate and celebrate "the rich diversity of life on Earth and inspire action to protect and conserve it through the power of imagery."

The competition is chaired by award-winning wildlife photographer Suzi Eszterhas. This year there were more than 6,500 entries.

These images originally appeared in bioGraphic, an online magazine about science and sustainability and the official media sponsor for the California Academy of Sciences' BigPicture:Natural World Photography Competition.

Here's a look at some of the winners and finalists.

'The Human Touch'

'The Human Touch'. (Photo: James Gifford/BigPicture: Natural World Photography Competition)

A couple of mountain gorillas at Virunga National Park in the Democratic Republic of the Congo recently posed for selfies. That image was fun, but this photo by James Gifford is incredibly touching. Winner of the Human/Nature category, it captures André Bauma, the head caretaker at the park's Senkwekwe Center for orphaned gorillas, with one of the animals in his care.

Bauma is raising the orphaned apes in hopes of releasing them back into the park. In the meantime, though, the gorillas treat him and his team as their family.

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

'Losing Wings'

'Losing Wings'. (Photo: Piotr Naskrecki/BigPicture: Natural World Photography Competition.)

Photographed at Gorongosa National Park in Mozambique, this year's Winged Life winner features mound-building termites. Once a year, when the first heavy rains signal the end of the dry season, millions of these subterranean insects appear, emerging dramatically in a massive, synchronized flight.

"A few minutes after landing on the ground, most individuals break off their wings and start looking for partners," says scientist and photographer Piotr Naskrecki.

In just a day, the ground is carpeted with their discarded wings, providing interesting walkways for all sorts of other creatures — including the winged carpenter ants in Naskrecki's photo, which had just completed their own mating flight.

'Duality'

'Duality'. (Photo: Armand Sarlangue/BigPicture: Natural World Photography Competition.)

The ethereal beauty of Norway's Senja Island is showcased by Segla, the mountain shown here that towers about 2,100 feet (650 meters) above the sea. Reindeer still roam here while humpback whales, orcas and sea eagles are found along the fjords.

Until recently, the area's ecosystems were at risk from the fossil fuel industry. But earlier this year, Norway's Labor Party voted to permanently protect Senja and the surrounding islands and waterways in the Norwegian Arctic from oil drilling and exploration.

Armand Sarlangue's photo of Senja Island is the winner in the Landscapes, Waterscapes and Flora category.

'Sea Dragon'

'Sea Dragon'. (Photo: Pier Mané/BigPicture: Natural World Photography Competition.)

Marine iguanas (Amblyrhynchus cristatus) of the Galapagos Islands are the only lizards that head to the ocean floor. Because food is scarce along the volcanic coastlines, they have evolved to forage at sea, grazing on algae in the water.

Pier Mané captures the winning photo in the Aquatic Life category with an iguana dining on green and red algae. Nutritious meals, however, aren't always easy to find. As bioGraphic reports, warmer waters brought by El Niño can replace algae with seaweeds that are harder to digest. Because this can harm iguana populations, the reptiles have evolved an ingenious trick that enables many of them to survive: shrinking to reduce the number of calories they need.

'Clouds of Salt'

'Clouds of Salt'. (Photo: Chiara Salvadori/BigPicture: Natural World Photography Competition.)

As photojournalist Chiara Salvadori stood on the high plains of northwestern Argentina, she was surround by Salar de Antofalla, one of the world's largest salt pans. Standing at 12,795 feet (3,900 meters), she watched the beauty as the landscape's moody colors changed, shaped by the shadows of the fast-moving clouds overhead.

One of the things that stood out most to Salvadori, she says, was the absence of humanity. Shaped mostly by wind and drought, the Salar’s salt bed supports very little life, with only the hardiest plants and animals surviving.

Salvadori's photo is the competition's Art of Nature winner.

'Curiosity'

'Curiosity'. (Photo: MikhailKorostelev/BigPicture: Natural World Photography Competition.)

To capture his winning shot in the Terrestrial Wildlife category, Mikhail Korostelev went to the South Kamchatka Sanctuary, a federally protected reserve on the tip of Russia's easternmost peninsula. The sanctuary is home to the largest population of protected brown bears in Russia, and the sanctuary's rivers host some of the largest salmon runs along the Pacific Coast.

Korostelev submerged a remotely operated camera along the Ozemaya River, one of the bears' favorite fishing spots, and waited. Soon, a curious bear explored the interesting object sitting on the river bottom and, as it started to investigate, Korostelev, snapped this photo.

'Boneyard Waltz'

'Boneyard Waltz'. (Photo: Daniel Dietrich/BigPicture: Natural World Photography Competition.)

Photographer Daniel Dietrich was a finalist in the Terrestrial Wildlife category with this image of polar bears walking by a pile of whale bones in Kaktovic, Alaska. Their noses are bloodstained, hinting that they recently enjoyed a meal of their own.

Polar bears are top predators in Arctic ecosystems and typically hunt alone, except when learning from their mothers, like the siblings in this photo. Eventually these bears will become solitary hunters in the Arctic National Wildlife Refuge, an area that is also luring a different kind of exploration because it holds an estimated 7.7 billion barrels of oil.

Dietrich says the smallest bear in the photo turned to watch a large male following the group before the trio slipped into the waters of the Beaufort Sea.

'Bohemian Skirt'

'Bohemian Skirt'. (Photo: Jinggong Zhang/BigPicture: Natural World Photography Competition.)

When threatened, the female palmate octopus (Tremoctopus gracilis) will extend her skirt-like membrane and wave it about like a banner. This dramatic, billowing display increases the size of her silhouette and can sometimes be enough to ward off predators.

Photographer Jinggong Zhang captured this survival strategy in Anilao, Philippines, with his image earning finalist recognition in the Aquatic Life category.

'Resilience'

'Resilience'. (Photo: Julie Fletcher/BigPicture: Natural World Photography Competition.)

In 2018, photographer Julie Fletcher set out to document the fire-ravaged forests on Kangaroo Island off South Australia. The country was experiencing its third-hottest year on record. High temperatures and droughts combined to create perfect conditions for brush fires. Slow-moving koalas often couldn't survive the fast-burning blazes.

Fletcher watched as a determined koala with charred fur climbed a tree and began to munch burned leaves. "He was watching me the whole time," she says, "with an intensity that told the story."

Fletcher's photo was a finalist in the Terrestrial Wildlife category.

'Traveling to the Edge'

'Traveling to the Edge'. (Photo: Eleazer/BigPicture: Natural World Photography Competition.)

In this Terrestrial Wildlife finalist photo, Buddy Eleazer captured a gemsbok (Oryx gazella) in the Namib-Naukluft Desert in Namibia. The antelope sends a spray of fine sand as it makes its way across a dune.

Along the ridgeline, the gemsbok will inhale a cool, moist breeze blowing in from the Atlantic Ocean. By breathing in this cooler air, the animal can reduce the temperature of the blood heading toward its brain, helping it recover from overheating in such an unforgiving environment.