Daniel J. Cox / Gray Wolf (Canis lupus) predating female Elk (Cervus elaphus) crossing river, Alum Creek, Yellowstone National Park, Wyoming, sequence 4 of 4

Daniel J. Cox / Gray Wolf (Canis lupus) killing female Elk (Cervus elaphus) crossing river, Alum Creek, Yellowstone National Park, Wyoming, sequence 3 of 4

Daniel J. Cox / Gray Wolf (Canis lupus) attacking female Elk (Cervus elaphus) crossing river, Alum Creek, Yellowstone National Park, Wyoming, sequence 2 of 4

Daniel J. Cox / Gray Wolf (Canis lupus) pair predating female Elk (Cervus elaphus) crossing river, Alum Creek, Yellowstone National Park, Wyoming, sequence 1 of 4

Daniel J. Cox / Gray Wolf (Canis lupus) pack on ridge in winter, Lamar Valley, Yellowstone National Park, Wyoming

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.

Andy Rouse / Grey wolf (Canis lupus lupus) Finland, September.

Juergen Freund / Dingo (Canis lupus dingo) at Devils Marbles, Northern Territory, Australia.

Roland Seitre / Arabian wolf (Canis lupus arabs) running. Captive, occurs in Israel, Iraq, Oman, Yemen, Jordan and Saudi Arabia.

Roland Seitre / Arabian wolf (Canis lupus arabs) running over sand. Captive, occurs in Israel, Iraq, Oman, Yemen, Jordan and Saudi Arabia.

Edwin Giesbers / Wide angle close-up of a European grey wolf (Canis lupus) in landscape, captive, Norway, February.