|C. l. occidentalis at the Grizzly and Wolf Discovery Center at West Yellowstone, Montana.|
|Subspecies:||C. l. occidentalis|
|Canis lupus occidentalis
|C. l. occidentalis range (green)|
The northwestern wolf (Canis lupus occidentalis), also known as the Mackenzie Valley wolf, British Columbia wolf or northern timber wolf is a subspecies of gray wolf which ranges from the upper Mackenzie River Valley, southward into central Alberta. Along with C. l. nubilus, C. l. occidentalis is the most widespread member of the five gray wolf subspecies in North America, with at least six different synonyms.
The subspecies was first written of by Scottish naturalist Sir John Richardson in 1829. He chose to give it the name occidentalis in reference to its geographic location rather than label it by its color, as it was too variable to warrant such. Phylogenetic analyses of North American gray wolves show that there are three clades corresponding to C. l. occidentalis, C. l. nubilus and C. l. baileyi, each one representing a separate invasion into North America from distinct Eurasian ancestors. C. l. occidentalis, the most northwestern subspecies, is descended from the last gray wolves to colonize North America. It likely crossed into North America through the Bering land bridge after the last ice age, displacing C. l. nubilus populations as it advanced, a process which has continued till present times.
The northwestern wolf is one of the largest gray wolves in North America, and varies greatly in color from black to pure white. The average weight of 147 wolves captured in Denali National park between 1986 and 1994 was 40 kilograms (88 lb) for females and 47 kilograms (104 lb) for males. The heaviest recorded specimen was killed on 70 Mile River in east-central Alaska on July 12, 1939 and weighed 79.4 kilograms (175 lb). Sir John Richardson described the northwestern wolf as having a more robust build than the European Wolf, with a larger, rounder head and a thicker, more obtuse muzzle. Its ears are also shorter, and its fur bushier.
- Wozencraft, W. C. (2005). "Order Carnivora". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Mech, L. David (1981), The Wolf: The Ecology and Behaviour of an Endangered Species, University of Minnesota Press, p. 352, ISBN 0-8166-1026-6
- Snyder, S. A. 1991. Canis lupus. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2013, November 27].
- Chambers SM, Fain SR, Fazio B, Amaral M (2012). "An account of the taxonomy of North American wolves from morphological and genetic analyses". North American Fauna 77: 1–67. Retrieved 2013-07-02.
- Richardson, J. (1829) Fauna boreali-americana, or, The zoology of the northern parts of British America, London : J. Murray [etc.], pp. 60-65
- Mech, L. D. (2003). The Wolves of Denali. University of Minnesota Press. pp. 39-40. ISBN 0816629595.
- Lopez, Barry H. (1978). Of Wolves and Men. J. M. Dent and Sons Limited. p. 18. ISBN 0-7432-4936-4.
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