Gray Wolf (Canis lupus) Fact Sheet: Physical Characteristics

General body size

• Largest, non-domestic canine (Mech and Boitani 2004)
  • Similar to a German shepherd dog except with longer legs and larger feet (Mech and Boitani 2004)
  • Length comparable to the average height of a human, slightly shorter c. 5-6.5 ft (Mech 1970)
    • Tail length included in larger size range
  • Standing, shoulder height: 26-36 inches (Mech 1970)

Weight

• Highly variable
• Adult range: 13-78 kg (29-172 lb) (Mech and Boitani 2003)
  • Smallest subspecies inhabits the Israeli desert
  • Largest subspecies inhabits the northern tundra
  • See subspecies table below for details on selected Eurasian subspecies; note highly variable size within and between subspecies

Anatomy

• Chest narrow and keel-like (Mech 1970)
• Legs long (Mech and Boitani 2004)
  • Forelegs pressed inward, elbows turned in and paws turned out (Mech 1970)
  • Leg length promotes speed and ability to move in deep snow cover (Mech 1970)
• Feet flexible (Mech and Boitani 2004)
  • Toes: 4 on hindfoot; 5 on forefoot, only 4 touching the ground when walking (Mech 1970)
    • Each with large, calloused pad (Mech 1970)
    • Non-retracting claws, useful for digging and scrambling up steep, loose surfaces (Mech 1970)
    • Heel pad large (Mech 1970)
• Skull elongate (Mech 1970)
  • Olfactory region of nasal cavity large; 14 times that of humans (Mech 1970)
• Teeth: 42 total; canines (reaching 2.25 in) are the largest (Mech 1970)
  • Canines and incisors hold prey
    • Gap between canine and first pre-molar increase efficiency
  • Carnassials (flesh teeth) chew flesh
  • Massive molars crush bone

Coat/Pelage

• Soft, dense underhair, overlaid by guard hair; arranged in irregular rows (Mech 1970)
  • Underhairs short and fine
  • Guard hair determines perceived color
    • Long, stiff hairs of the outer coat
• Mane; erectile hairs along the back of the neck and shoulders (Mech 1970)
  • Raised when angry
• Color highly variable within and between populations
  • Litter mates often with dissimilar color (Mech 1970; Mech and Boitani 2003)
  • White, cream-colored, buff, tawny, reddish, gray, black; mottled combinations thereof (Mech 1970)
  • All-black individuals uncommon in most populations, though in high frequency in some forested areas (Anderson et al. 2009)
    • Rare in wolves of the North American tundra; increasing in frequency in more southerly, forested areas (Anderson et al. 2009)
  • Early hybridization with domestic dogs introduced melanism (all-black coat) into wolves in North American and Italy (Anderson et al. 2009)
    • Genetic introgression from domestic dogs may provide a selective advantage for all-black wolves in North American forests (Anderson et al. 2009)
• Graying with age (Anderson et al. 2009)

• Males larger than females (Mech 2008)

Sense of smell

• Superior
• 100-1,000,000 times more sensitive to odor than humans (Harrington and Asa 2003)
• Three olfactory systems
  • Main olfactory system characterized by the densely grouped olfactory receptors and high surface area inside the nose (Harrington and Asa 2003)
    • Large olfactory receptor area and numerous active chemoreceptors (Harrington and Asa 2003; Zhang et al. 2011)
    • c. 280 million olfactory receptors; more than the number of visual receptors in the retina (Wieland 1938, as cited in Moulton 1967)
  • Accessory olfactory system; receives signals from the vomeronasal organ (VNO) and possibly linked to sexual response
  • Trigeminal olfactory system; receives signals from olfactory and respiratory epithelium and primarily responds to noxious chemicals (Harrington and Asa 2003)

Vision

• See the world "faster" than humans; better temporal resolution allowing wolves to track movement on a fine scale (Harrington and Asa 2003; Horowitz 2010)
  • Eg. when watching TV, humans see a smooth progression of events from one frame to the next; dogs (and by extension wolves) see the dark gaps between each frame (Horowitz 2010)
  • Due to the large number of rods (a type of photoreceptor), over 2 times the number compared to humans (based on summary of research reported by Harrington and Asa 2003)
• Color vision restricted to blue and green; the color "red" might appear as a faint shade of green to a canid (Harrington and Asa 2003)
• Acuity may be sharper in wolves than in dogs (Harrington and Asa 2003)
  • Ganglionic cells more numerous in wolves; sharp vision along much of the visual horizon without having to shift gaze
• Capable of sight even in low light (Harrington and Asa 2003)
  • Tapetum lucidum, cellular layer behind the retina that directs light back toward photoreceptors
    • Responsible for "eyeshine", commonly observed in many nocturnal animals
    • Shape and position reflects light gathered from at and below the visual horizon

• 39 chromosome pairs (2n=78) (Wayne 1993)

Size 

• Smallest North American subspecies (McBride 1980)
  • Head and body length, nose to tail
    •  168 cm (c. 5.5 ft)
  • Shoulder height: 71-81 cm (28-32 in)
  • Weight range: 23-41 kg (50-90 lb) (McBride 1980; USFWS webpage)

Coat/Pelage

• Color highly variable, as with all wolves (McBride 1980)
• No solid black or white variants

Coat color is highly variable in the gray wolf.

Image credits: top, © Christian Mehlfuhrer from WikiMedia Commons, some rights reserved; middle, © Metassus from Flickr, some rights reserved; bottom, © Quartle from WikiMedia Commons. Some rights reserved.

Anderson et al. (2009)
Ferguson (1981)
Harrison (1968)
Harrington and Asa (2003)
Geptner et al. (1998)
Horowitz (2009)
Kingdon (1991)
McBride (1980)
Mech (1970, 2008)
Mech and Boitani (2003, 2004)
Mendelssohn (1982)
Moulton (1967)
Nowak (1999)
Ognev (1962)
Parson and Nicholopoulos (1995)
Shrestha (1997)
USFWS webpage
Wayne (1993)
Zhang et al. (2011)