Heather Angel / Giant panda (Ailuropoda melanoleuca) sliding down slope on back after losing footing. Panda Breeding Centre, Wolong, Sichuan, China. January 1987.

Diane McAllister / Polar bears (Ursus maritimus) fighting in water. Beaufort Sea , Kaktovik, Alaska, USA. Highly commended in the Polar Passion category of the Nature's Best Photography Competition 2019.

Jami Tarris / Polar Bear (Ursus maritimus) cooling off, Spitsbergen, Svalbard, Norway

Jami Tarris / Polar Bear (Ursus maritimus) hunting Bearded Seal (Erignathus barbatus) pup, Spitsbergen, Svalbard, Norway

Jami Tarris / Polar Bear (Ursus maritimus) on ice floe, Spitsbergen, Svalbard, Norway

Jami Tarris / Polar Bear (Ursus maritimus) on shore, Spitsbergen, Svalbard, Norway

Danny Green / Polar bear (Ursus maritimus) walking across sea ice, reflected in water. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) female resting with cubs on glacier. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) female and cubs feeding on Whale carcass. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and two cubs feeding on Whale carcass. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and cubs, standing on sea ice. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and cubs resting on sea ice. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) female and cubs, one cub walking up slope of ice in foreground. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and cubs feeding on Whale carcass. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) and cubs feeding on Whale carcass, on iceberg. Svalbard, Norway, July 2018.

Danny Green / Polar bear (Ursus maritimus) walking across ice, snow covered mountain in background. Svalbard, Norway, April 2018.

Danny Green / Polar bear (Ursus maritimus) resting in snow. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) licking paw, close-up. Svalbard, Norway, April.

Danny Green / Polar bear (Ursus maritimus) standing on glacier. Svalbard, Norway, July 2018.

Danny Green / Polar bear (Ursus maritimus) standing on ice. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) looking for food on ice. Svalbard, Norway, April.

Danny Green / Polar bear (Ursus maritimus) male standing beside rocks in frozen and snow covered landscape. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male walking across frozen landscape. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male in snow. Svalbard, Norway, April.

Danny Green / Polar bear (Ursus maritimus), male and female approaching each other across snow covered rocky landscape. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male approaching female on snow covered hill top. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male approaching female in rocky area covered in snow. Svalbard, Norway, April 2019.

Danny Green / RF - Polar bear (Ursus maritimus) male walking through snow covered landscape, mountains in background. Svalbard, Norway, April (This image may be licensed either as rights managed or royalty free.)

Danny Green / RF - Polar bear (Ursus maritimus) cub walking in snow. Svalbard, Norway, April. (This image may be licensed either as rights managed or royalty free.)

Danny Green / RF - Polar bear (Ursus maritimus) female walking across ice. Svalbard, Norway, April. (This image may be licensed either as rights managed or royalty free.)

Danny Green / Polar bear (Ursus maritimus) female and cubs play fighting. Svalbard, Norway, March 2018.

Danny Green / Polar bear (Ursus maritimus) two walking in snowy landscape. Svalbard, Norway, April 2018.

Danny Green / Polar bear (Ursus maritimus) male female pair looking upwards, snow covered hills in background. Svalbard, Norway, April 2018.

Danny Green / Polar bear (Ursus maritimus) group on ice, female and cubs feeding on Whale carcass. Svalbard, Norway, June 2018.

Danny Green / Polar bear (Ursus maritimus) resting on sea ice, view from above. Svalbard, Norway, June 2018.

Danny Green / Polar bear (Ursus maritimus) sleeping in snow. Churchill, Manitoba, Canada, November.

Danny Green / Polar bear (Ursus maritimus) hunting Seal on sea ice. Svalbard, Norway, July 2018.

Danny Green / Polar bear (Ursus maritimus), two cubs playing, leaping across sea ice, reflected in water. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus), two cubs walking on sea ice. Svalbard, Norway, July.

Danny Green / Polar bear (Ursus maritimus) cub ready to jump down from pack ice. Svalbard, Norway, April.

Nick Garbutt / Western red panda (Ailurus fulgens fulgens) climbing in tree. Singalila National Park, India / Nepal border.

Heather Angel / Giant panda (Ailuropoda melanoleuca) portrait, in falling snow. Captive bred, in enclosure, Panda Breeding Centre, Wolong, Sichuan Province, China. February 2008.

Mark Raycroft / Grizzly Bear (Ursus arctos horribilis) on road, North America

Mark Raycroft / Grizzly Bear (Ursus arctos horribilis), North America

Mark Raycroft / Grizzly Bear (Ursus arctos horribilis) crossing road, North America

Mark Raycroft / Grizzly Bear (Ursus arctos horribilis), North America

Mark Raycroft / Grizzly Bear (Ursus arctos horribilis), North America

John Shaw / Brown bear (Ursus arctos) searching for clams on tidal mudflat with waterbirds. Lake Clark National Park, Alaska. August.

Nick Hawkins / Steller's sea lions (Eumetopias jubatus) off the coast of the Great Bear Rainforest, near Bella Bella, British Columbia, Canada. August

Nick Hawkins / A female American black bear (Ursus americanus) and her young cub, Nova Scotia, Canada. July.

Marie Read / Black-necked stilts (Himantopus mexicanus) pair performing post-copulatory display (as copulation ends, the male slides off the female leaving his wings draped over her and crossing his bill with hers...

Marie Read / American avocets (Recurvirostra americana) two during aggressive (territorial) encounter, Bear River Migratory Bird Refuge, Utah, USA, May.

Suzi Eszterhas / Giant panda (Ailuropoda melanoleuca) sitting with Bamboo in background. Shenshuping Panda Base, Wolong Nature Reserve, Wenchuan, Sichuan Province, China. Captive.

Marion Vollborn/ BIA / Polar Bear (Ursus maritimus) on ice, Svalbard, Norway

Marion Vollborn/ BIA / Polar Bear (Ursus maritimus) waiting at breathing hole for seals, Svalbard, Norway

Marion Vollborn/ BIA / Polar Bear (Ursus maritimus), Svalbard, Norway

Marion Vollborn/ BIA / Polar Bear (Ursus maritimus), Svalbard, Norway

Jeff Foott / Bear Grass (Xerophyllum tenax) flowering, Mount Reynolds, Glacier National Park, Montana

Jed Weingarten / Wild Wonders of China / Asian black bear (Ursus thibetanus) feeding on leaves, Tangjiahe Nature Reserve, Sichuan Province, China, April.

Sven Zacek / Brown bear (Ursus arctos) in coniferous forest. Ida-Virumaa, Eastern Estonia. September.

Pal Hermansen / Brown bear (Ursus arctos), two showing aggression at night. Finland. August.

Pal Hermansen / Bear (Ursus arctos) silhouetted at night under starry sky. Finland. August.

Chase Dekker / Brown Bear (Ursus arctos) in river, Katmai National Park, Alaska

Sean Crane / Grizzly Bear (Ursus arctos horribilis) with Coho Salmon (Oncorhynchus kisutch) prey, Lake Clark National Park, Alaska

Juergen & Christine Sohns / Koala (Phascolarctos cinereus), Parndana, Kangaroo Island, South Australia, Australia

David Perpinan / Close-up of a Giant anteater (Myrmecophaga tridactyla) eating ants, Pantanal, Mato Grosso do Sul, Brazil.

Sylvain Cordier / Polar bear (Ursus maritimus), female with two cubs, on a barrier island outside Kaktovik, Alaska, USA.

Nick Garbutt / Giant anteater (Myrmecophaga tridactyla) foraging in palm savannah grasslands. Southern Pantanal, Moto Grosso do Sul State, Brazil. September.

Danny Green / Brown bear (Ursus arctos) in autumnal forest, Finland, September

Danny Green / Brown bear (Ursus arctos) in autumnal forest, Finland, September

Danny Green / Brown Bear (Ursus arctos) in the snow, Finland, April

Edwin Giesbers / Giant panda (Ailuropoda melanoleuca) in snow, captive.

Eric Baccega / Giant panda (Ailuropoda melanoleuca) cub playfuly chewing a bamboo stick. Yuan Meng, first giant panda ever born in France, is now 10 months old and still feeds on his mother's milk, Captive at Beauva...

Eric Baccega / Giant panda cub (Ailuropoda melanoleuca) portrait Yuan Meng, first giant panda ever born in France, age 10 months. Captive at Beauval Zoo, Saint Aignan sur Cher, France

Eric Baccega / Giant panda (Ailuropoda melanoleuca) cub playing on wooden structure. Yuan Meng, first giant panda ever born in France, age 10 months, Captive at Beauval Zoo, Saint Aignan sur Cher, France

Eric Baccega / Giant panda (Ailuropoda melanoleuca) cub playing on wooden structure. Yuan Meng, first giant panda ever born in France, age 10 months, Captive at Beauval Zoo, Saint Aignan sur Cher, France

Eric Baccega / Giant panda (Ailuropoda melanoleuca) cub exploring during its outings in the enclosure. Yuan Meng, first giant panda ever born in France, age 10 months, Captive at Beauval Zoo, Saint Aignan sur Cher,...

Eric Baccega / Giant panda (Ailuropoda melanoleuca) female, Huan Huan, out in her enclosure in mist, Captive at Beauval Zoo, Saint Aignan sur Cher, France. The mist is created artificially by machine, in order to cr...

Eric Baccega / Giant panda (Ailuropoda melanoleuca) female, Huan Huan, out in her enclosure in mist, Captive at Beauval Zoo, Saint Aignan sur Cher, France The mist is created artificially by machine, in order to cr...

Andy Rouse / Polar bear (Ursus maritimus) standing on pack ice at the water's edge, Svalbard, Norway. June.

Eric Baccega / Portrait of Giant panda cub (Ailuropoda melanoleuca) captive. Yuan Meng, first Giant panda ever born in France, now aged 8 months, Beauval Zoo, France

Donald M. Jones / Brown Bear (Ursus arctos) feeding on dandelions, western Canada

Donald M. Jones / Brown Bear (Ursus arctos) feeding on dandelions, western Canada

Donald M. Jones / Black Bear (Ursus americanus) cub in tree, western Canada

Yashpal Rathore / Sloth bear (Melursus ursinus) cubs riding on mothers back, Daroiji Bear Sanctuary, Karnataka, India.

Yashpal Rathore / Sloth bear (Melursus ursinus) cub riding on mothers back, Daroiji Bear Sanctuary, Karnataka, India.

Philippe Clement / Red panda (Ailurus fulgens) eating bamboo leaves. Captive, native to the eastern Himalayas and southwestern China.

Staffan Widstrand / Wild Wonders of China / Red panda or Lesser panda (Ailurus fulgens) in the humid montane mixed forest, Laba He National Nature Reserve, Sichuan, China

Danny Green / Grizzly Bear (Ursus arctos) eating a fish, Lake Clarke National Park, Alaska, August

Philippe Clement / Juvenile European brown bear cub (Ursus arctos arctos) walking in deep snow in winter, Bavarian Forest National Park, Germany, January. Captive.

Philippe Clement / European brown bear (Ursus arctos arctos) cubs suckling from mother in the snow in winter, Bavarian Forest National Park, Germany, January. Captive.

Ingo Arndt / Polar Bear (Ursus maritimus) on icefield with moon in late winter, Svalbard, Spitsbergen, Norway, April

Roy Mangersnes / Juvenile female Polar bear (Ursus maritimus) rolling, playing with ice in a fjord, Svalbard, Norway, March.

Roy Mangersnes / Juvenile female Polar bear (Ursus maritimus) hunting for seals at breathing holes in the ice, Svalbard, Norway, March.

Roy Mangersnes / Juvenile female Polar bear (Ursus maritimus) lying down protecting a seal carcass at sunset, Svalbard, Norway, March.

Steven Kazlowski / Polar bear (Ursus maritimus) mother with two juveniles walking along ice edge during autumn freeze up, Beaufort Sea, off Arctic coast, Alaska