Jeff Wilson / Adult Arctic wolf (Canis lupus) Ellesmere Island, Nunavut, Canada, June 2008. Taken on location for BBC series, Frozen Planet, Summer

Jeff Wilson / Arctic wolf (Canis lupus) on tundra, Ellesmere Island, Nunavut, Canada, June 2008. Taken on location for BBC series, Frozen Planet, Summer

Jeff Wilson / Silhouette of Arctic wolf (Canis lupus) on sea ice, Ellesmere Island, Nunavut, Canada, June 2008. Taken on location for BBC series, Frozen Planet, Summer

Jeff Wilson / Two Arctic wolves (Canis lupus) in tundra landscape, Ellesmere Island, Nunavut , Canada, June 2008, Taken on location for BBC series, Frozen Planet, Summer

Peter Cairns / European grey wolf (Canis lupus) portrait in snow, Tromso, Norway, captive, April

LYNN M. STONE / Arctic grey wolf {Canis lupus arctos} running through snow, USA. captive

Staffan Widstrand / Grey wolf running silhouetted {Canis lupus} Toropets, Russia.

Jim Brandenburg / Arctic Wolf (Canis lupus) pack hunting Muskox (Ovibos moschatus) herd, Ellesmere Island, Nunavut, Canada

Jim Brandenburg / Arctic Wolf (Canis lupus) juvenile male babysitting pups, Ellesmere Island, Nunavut, Canada

Jim Brandenburg / Arctic Wolf (Canis lupus) alpha male known as Buster, smelling Arctic Poppy (Papaver lapponicum) flowers, Ellesmere Island, Nunavut, Canada

Tom Vezo / Arctic Wolf (Canis lupus) portrait of white wolf with ice on its chin, Idaho

Jim Brandenburg / Arctic Wolf (Canis lupus) pups, Ellesmere Island, Nunavut, Canada