The sea leopard. The Antarctic Peninsula. (Photo by Paul Nicklen)

A gentoo penguin chick peeks, checking for patrolling leopard seals before tempting fate. (Photo by Paul Nicklen/National Geographic). Port Lockroy, Antarctic Peninsula, 2011

Young chinstrap penguins resting on an ice floe at the Anvers Island, Antarctica. (Photo by Paul Nicklen)

Narwhals, raising their tusks, float to the surface to breathe. Lancaster Saund, Nunavut, Canada. (Photo by Paul Nicklen)

Arctic tern circling in search of profit. Arctic. (Photo by Paul Nicklen)

The female polar bear studies human habitation, after the seat broke on a snowmobile, backpack for camera and hat Paul Nickle. It is best not to get in the way of bears, when they are hungry. (Photo by Paul Nicklen)

Thick-billed murre ((Latin. Uria lomvia) thrown into the water at Bear Island (Bjørnøya Island), Svalbard. For the sake of the fish the birds dive to a depth of 150 meters. In winter, birds fly to winter in Greenland and Iceland. (Photo by Paul Nicklen)

Walrus. (Photo by Paul Nicklen)

Spring in the Arctic, traces of meltwater runoff sprawled on the ice. (Photo by Paul Nicklen)

Papuanskie Penguins. Port Lockroy, The Antarctic Peninsula. (Photo by Paul Nicklen)

A young polar bear leaps between ice floes. (Photo by Paul Nicklen/National Geographic). Barents Sea, Svalbard, Norway, 2011

Polar bear and her two young drift on an ice floe. Gudzonov diarrhea, Nunavut, Canada. (Photo by Paul Nicklen)