An adult female Harp Seal (Pagophilus groenlandicus) surfaces in a breathing hole she has maintained in the floating pack ice of the Gulf of St. Lawrence, near where her young pup is resting on the ice.

Gulf of St. Lawrence, Nova Scotia, Canada.

A young Harp Seal pup (Pagophilus groenlandicus) rests on the sea ice where it was born. The pup is less than two weeks old.

Gulf of St. Lawrence, Nova Scotia, Canada.

Two large, mature adult male polar bears (Ursus maritimus) confront one another on the sea ice at a seal kill site. Arctic Ocean north of the Svalbard Archipelago, near 81-degrees North.

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Twin polar bear cubs (Ursus maritimus), about three months old, inside a snow den. Polar bear maternity denning area, Wapusk National Park, Western Hudson Bay, Manitoba, Canada.

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An Atlantic Walrus (Odobenus rosmarus rosmarus) mother and calf rest on sea ice in the Barents Sea (Arctic Ocean) near Stoliczka Island in Franz Josef Land, Russia.

Atlantic Walruses (Odobenus rosmarus rosmarus) swimming as a herd in northern Novaya Zemlya, where the Barents Sea and Kara Sea meet, in the Russian High Arctic.

An adult Atlantic Walrus (Odobenus rosmarus rosmarus) surfaces to breath while swimming in the Arctic Ocean near Lagoya Island in the Svalbard Archipelago, Norway.

A Northern Sea Otter (Enhydra lutris kenyoni) rests on an iceberg in Prince William Sound, Alaska.

Northern Sea Otters (Enhydra lutris kenyoni) resting together on an iceberg in Prince William Sound, Alaska.

Northern Sea Otters (Enhydra lutris kenyoni) resting together on an iceberg, Prince William Sound, Alaska.

Orcas (Orcinus orca), also known as killer whales, in Prince William Sound, Alaska.

As the arctic climate warms, killer whales are expanding their range northward.

An adult Harbor Seal (Phoca vitulina) resting on ice near Surprise Glacier, Harriman Fjord, Prince William Sound, Alaska.

As the climate warms, Harbor Seals are expanding their range northward.

An adult polar bear (Ursus maritimus) swims stealthily among floes of ice in the Arctic Ocean north of the Svalbard Archipelago, Norway.

To see more polar bears, please browse the separate polar bear image collections.

An adult male polar bear (Ursus maritimus) "still-hunting" on sea ice -- waiting for an opportunity to grab an unsuspecting seal as it surfaces to breathe. Arctic Ocean north of the Svalbard Archipelago, near 81-degrees North.

To see more polar bears, please browse the separate polar bear image collections.

Adult male polar bears (Ursus maritimus) sparring playfully on sea ice. Hudson Bay, Manitoba, Canada.

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An adult male polar bear (Ursus maritimus) lies on sea ice while "still-hunting" -- waiting for an opportunity to grab a seal as it surfaces to breathe. Hudson Bay, Manitoba, Canada.

To see more polar bears, please browse the separate polar bear image collections.

An adult male Hooded Seal (Cystophora cristata) on sea ice. He has inflated the bladder characteristic of the species -- the "hood," an elastic inflatable sac -- which extents from his nose to his forehead on top of his head.

Gulf of St. Lawrence, Canada

A newborn Hooded Seal pup (Cystophora cristata) lies next to its mother on the floating sea ice where the pup was born.

Gulf of St. Lawrence, Nova Scotia, Canada.

Pacific Walruses (Odobenus rosmarus divergens) maneuver for position at a small crowded haul-out on Arakamchechen Island in the Bering Sea, Chukotka, Russia.

Pacific Walruses (Odobenus rosmarus divergens) maneuver for position at a small, crowded haul-out on Arakamchechen Island in the Bering Sea, Chukotka, Russia.

Pacific Walruses (Odobenus rosmarus divergens) maneuver for position at a small, crowded haul-out on Arakamchechen Island in the Bering Sea, Chukotka, Russia.

A Pacific Walrus (Odobenus romarus divergens) at a small, crowded haul-out on Arakamchechen Island in the Bering Sea, Russia.

A Svalbard Reindeer (Rangifer tarandus platyrhynchus) jumping as it travels across the tundra at Eidembukta on Spitsbergen in the Svalbard Archipelago, Norway.

A reindeer antler (Rangifer tarandus) lying on the Arctic tundra, Wrangel Island, Russia.

An adult male Musk Ox (Ovibos moschatus) on autumn tundra at Blomsterbugten, Kejser Franz Joseph Fjord, Northeast Greenland National Park, Greenland.

An adult male Musk Ox (Ovibos moschatus) at Blomsterbugten, Kejser Franz Joseph Fjord, Northeast Greenland National Park, Greenland.

An adult Arctic Fox (Alopex lagopus), in dark summer pelage, carrying a fledgling Black-legged Kittiwake (Rissa tridactyla) it has just killed at a seabird colony in Diskobukta on Edgeoya in the Svalbard Archipelago, Norway.

An adult Arctic Fox (Alopex lagopus), in dark summer pelage, carrying a fledgling Black-legged Kittiwake (Rissa tridactyla) it has just killed at a seabird colony in Diskobukta on Edgeoya in the Svalbard Archipelago, Norway.

Pacific Walruses (Odobenus rosmarus divergens), including mothers with calves, are hauled out and jammed together on a very small stretch of rocky shore backed by nearly-shear cliffs on Herald Island in the Chukchi Sea (Arctic Ocean), Russia.

Atlantic Walruses (Odobenus rosmarus rosmarus) resting and swimming near shore at a small haul-out on Ostrova Oranskie, northern Novaya Zemlya, where the Barents Sea and Kara Sea meet, in the Russian High Arctic.

An adult Atlantic Walrus (Odobenus rosmarus rosmarus) surfaces to breath while swimming in the Arctic Ocean near Lagoya Island in the Svalbard Archipelago, Norway.

Pacific Walruses (Odobenus rosmarus divergens) hauled out and jammed together on a very small stretch of rocky shore backed by nearly-shear cliffs on Wrangel Island in the Chukchi Sea (Arctic Ocean), Russia.

Pacific Walruses (Odobenus rosmarus divergens) swim in the Bering Sea during a rainstorm at Cape Onman, Chukotka (Chukchi Peninsula, Siberia), Russia.

A polar bear mother (on right) and her twin cubs (about 2 years old) rest on a floe of sea ice in heavy fog at twilight, in the Arctic Ocean above 81-degrees North.

To see more polar bears, please browse the separate polar bear image collections.

A young polar bear cub, about six months old, follows its mother as she walks along the edge of shore-fast ice in Nordaustlandet in the Svalbard Archipelago.

To see more polar bears, please browse the separate polar bear image collections.

A polar bear mother shelters her twin cubs during a snowstorm. Wapusk National Park, Western Hudson Bay, Manitoba, Canada.

To see more polar bears, please browse the separate polar bear image collections.

A Harp Seal (Pagophilus groenlandicus) mother with her young "white-coat" pup, on the sea ice where the pup was born. The pup is less than two weeks old.

Gulf of St. Lawrence, Nova Scotia, Canada.

An adult Arctic Fox (Vulpes lagopus), in white winter pelage, resting in snow near the shore of Hudson Bay at sunset.

Wapusk National Park, Manitoba, Canada.

Steller Sea Lions (Eumetopias jubatus) swimming in the Bering Sea, Russia.

A Steller Sea Lion (Eumetopias jubatus) in Prince William Sound, Alaska.

A bull Steller Sea Lion (Eumetopias jubatus) with females and calves at a rookery in Prince William Sound, Alaska.

An adult Svalbard Reindeer (Rangifer tarandus platyrhynchus) on autumn tundra.

Near Kapp Lee, Edgeoya, Svalbard Archipelago, Norway.

The antler of a Svalbard Reindeer (Rangifer tarandus platyrhynchus), Signehamna in Lilliehook Fjorden, Spitsbergen, Svalbard. The distant glacier is Lilliehook Breen.

An adult Arctic Hare (Lepus arcticus), well-camouflaged in its white pelage, hunkers down during a snowstorm, next to a boulder for protection from the wind.

Near Churchill, Manitoba, Canada.

An Arctic Hare (Lepus arcticus) on rocky tundra at Blomsterbugten in the Kejser Franz Joseph Fjord system, Northeast Greenland National Park, Greenland.

Atlantic Walrus (Odobenus rosmarus rosmarus) mother and calf on sea ice in Barents Sea, near Stoliczka Island, Franz Josef Land, Russia.

Atlantic Walruses (Odobenus rosmarus rosmarus) on offshore rocks at Kvitoya (White Island), the easternmost island in the Svalbard Archipelago.

Atlantic walruses (Odobenus rosmarus rosmarus) resting and swimming near shore at a small haul-out on Ostrova Oranskie, northern Novaya Zemlya, where the Barents Sea and Kara Sea meet, in the Russian High Arctic.

An adult Atlantic Walrus (Odobenus rosmarus rosmarus) in the Arctic Ocean near the shore of Lagoya Island in the Svalbard Archipelago, Norway.

The skull of a subadult Pacific walrus (Odobenus rosmarus divergens) lying on the rocky tundra near the shore of Wrangel Island, Siberia, Russia.

A young Arctic Fox (Alopex lagopus), in dark summer pelage, crosses a fast-moving stream to hunt for Black-legged Kittiwakes (Rissa tridactyla) where the birds have a nesting colony in Diskobukta on Edgeoya in the Svalbard Archipelgo, Norway.

A young Arctic Fox (Alopex lagopus), in dark summer pelage, carrying a fledgling Black-legged Kittiwake (Rissa tridactyla) it has just killed at a seabird colony in Diskobukta on Edgeoya in the Svalbard Archipelago, Norway.

A Bearded Seal (Erignathus barbatus) resting on a small iceberg near the receding glacier front of Hamiltonbreen in Hamiltonbukta, Spitsbergen, Svalbard.

A Svalbard Reindeer (Rangifer tarandus platyrhynchus) in summer snowfall at Sundneset in Freemansundet on Barentsoya in the Svalbard Archipelago, Norway.

An adult female polar bear gazes out at the sea while stranded ashore due to lack of sea ice. Phippsoya, Svalbard, Norway

To see more polar bears, please browse the separate polar bear image collections.

An adult female polar bear snacks on seaweed while stranded ashore due to lack of sea ice. Phippsoya, Svalbard, Norway.

To see more polar bears, please browse the separate polar bear image collections.

Harbor Seals (Phoca vitulina) at Virgohamna on Danskoya in the Svalbard Archipelago, Norway.

As the arctic climate warms, Harbor Seals are expanding their range northward.

An adult Northern Sea Otter (Enhyrda lutris kenyoni) swimming in Prince William Sound, Alaska.

A bull Steller Sea Lion (Eumetopias jubatus) with females and calves at a rookery in Prince William Sound, Alaska.

A bull Steller Sea Lion (Eumetopias jubatus) at his rookery, Prince William Sound, Alaska.