Jasper Doest / Gray Wolf (Canis lupus) pack in the snow, Norway

John Shaw / Grey wolves running in snow (Canis lupus), Minnesota, USA. January. Controlled situation.

Klein & Hubert / Grey wolves (Canis lupus) pair and juvenile greeting each other, USA. Controlled conditions

Axel Gomille / Wolf (Canis lupus), young wolves play fighting in meadow, Saxony-Anhalt, Germany.

Nick Garbutt / Pack of wolves (Canis lupus). Yellowstone National Park, Wyoming, USA. January.

Eric Baccega / Pack of Grey wolves (Canis lupus) howling in the snow, captive. Bavarian Forest National Park, Germany, March. Captive.

Eric Baccega / Pack of Grey wolves (Canis lupus) greeting one another and expressing submissive behaviour,captive, Bavarian Forest National Park, Germany, July. Captive.

Will Burrard-Lucas / Ethiopian wolves (Canis simensis) individual from the BBC pack greeting each other after returning from hunting, Ethiopia.

Edwin Giesbers / Wide angle close-up of two European grey wolves (Canis lupus), captive, Norway, February.

Edwin Giesbers / Wide angle close-up of two European grey wolves (Canis lupus), captive, Norway, February.

Florian Möllers / Wolf (Canis lupus) pack running in deep snow, captive in enclosure of the Bavarian Forest National Park, Germany, February

XI ZHINONG / Grey Wolves (Canis lupus) hunting a wounded Tibetan wild ass (Equus kiang) Kekexili, Qinghai, China, December.

Staffan Widstrand / Eurasian / Grey wolf (Canis lupus) running through forest, Kuhmo, Finland. September.

Staffan Widstrand / Eurasian / Grey wolf (Canis lupus) watching flying flock of Common raven (Corvus corax) Kuhmo, Finland. September.

Roland Seitre / Polar Wolves (Canis lupus arctos), a high arctic variant of the Grey Wolf. Captive. Lobo Park, Antequera, Spain, January.

Edwin Giesbers / Grey wolf (Canis lupus) close up portrait, captive

Edwin Giesbers / Grey wolf (Canis lupus) close up, captive

Mark Carwardine / Eurasian / European / Forest Wolf (Canis lupus lupus) head portrait resting on ground. Mongolia, August.

Chadden Hunter / Cameraman Jeff Turner and Producer Chadden Hunter exposed at -40 degrees in Arctic circle in Northern Canada while filming wolves and bison hunting sequence. Taken on location for BBC Frozen Planet se...

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 / Two Arctic wolves (Canis lupus) in tundra landscape, 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

George Sanker / Portrait of Grey Wolf (Canis lupus). Yellowstone National Park, Wyoming, USA, October.

Grzegorz Lesniewski / Wild Carpathian Wolf (Canis lupus) running over snow. Bieszczady Mountains, the Carpathians, Poland, December.

Wild Wonders of Europe / Lesniewski / Portrait of a wild Carpathian Grey Wolf (Canis lupus lupus) in snow-bound woodland habitat. Bieszczady, Carpathian Mountains, Poland, December.

Jeff Vanuga / Gray Wolf (Canis lupus) running. Grand Teton National Park, Wyoming, September.

Jeff Vanuga / Silhouette of Gray Wolf (Canis lupus) standing on a rock by the Yellowstone River. Yellowstone National Park, USA,

Lassi Rautiainen / Brown bear (Ursus arctos) and Grey wolf (Canis lupus) together in wetlands, Kuhmo, Finland, July

Lassi Rautiainen / Grey wolf (Canis lupus) in woodland in thick snow jumping up at eagle perched on dead tree stump overhead, Finland, December

Lassi Rautiainen / Wild Grey wolf (Canis lupus) Kuhmo, Finland, September

Lassi Rautiainen / Wild Grey wolf (Canis lupus) walking, Kuhmo, Finland, September

Danny Green / 2020VISION / Red deer (Cervus elaphus) dominant stag amongst bracken, Bradgate Park, Leicestershire, England, UK, October. Did you know? In the past red deer were predated by wolves and to a lesser extent, lynx an...

Andy Rouse / Grey Wolf (Canis lupus) with clouds and a glacier in the distance. Katmai, Alaska, USA, August.

John Cancalosi / Grey Wolf (Canis lupus) head portrait of male, in snow, Captive

John Cancalosi / Grey Wolf (Canis lupus) head portrait of male, sleeping in snow, Captive

Chris O'Reilly / European grey wolf (Canis lupus lupus) immature, socialising with handler, Human interaction socialisation project, Wolf conservation, Scandinavia, Captive

Angelo Gandolfi / Head portrait of a Grey Wolf (Canis lupus) captive.

Angelo Gandolfi / A wild Grey Wolf (Canis lupus) roaming on the outskirts of a village at night, Tuscany "Maremma" Italy.

Eric Baccega / Two European grey wolves (Canis lupus) howling in winter landscape, captive. Bayerischerwald National Park, Germany.

Eric Baccega / European grey wolf (Canis lupus) howling in snow covered forest, captive. Bayerischerwald National Park, Germany.

Wild Wonders of Europe / Widstra / European / Grey wolf (Canis lupus) at sunset, Kuhmo, Finland, July 2009. WWE INDOOR EXHIBITION

Wild Wonders of Europe / Widstrand / European grey wolf (Canis lupus) carrying prey interacting with a European Brown bear (Ursus arctos) Kuhmo, Finland, July 2009

Wild Wonders of Europe / Widstrand / European grey wolf (Canis lupus) walking, Kuhmo, Finland, July 2009

Wild Wonders of Europe / Widstra / European grey wolf (Canis lupus) interacting with a European brown bear (Ursus arctos) Kuhmo, Finland, July 2009. WWE INDOOR EXHIBITION

Edwin Giesbers / Grey wolf (Canis lupus) head, captive

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

Wild Wonders of Europe / Widstrand / Wild European Grey wolf (Canis lupus) Kuhmo, Finland, September 2008