Canis lupus

Canis lupus

Description 15

The gray wolf is the largest extant member of the Canidae, excepting certain large breeds of domestic dog. Gray wolf weight and size can vary greatly worldwide, tending to increase proportionally with latitude as predicted by Bergmann's Rule, with the large wolves of Alaska and Canada sometimes weighing 3–6 times more than their Middle Eastern and South Asian cousins. On average, adult wolves measure 105–160 cm (41–63 in) in length and 80–85 cm (31–33 in) in shoulder height. The tail measures 29–50 cm (11–20 in) in length. The ears are 90–110 mm (3.5–4.3 in) in height, and the hind feet are 220–250 mm (8.7–9.8 in). The mean body mass of the extant gray wolf is 40 kg (88 lb), with the smallest specimen recorded at 12 kg (26 lb) and the largest at 79.5 kg (175 lb). Gray wolf weight varies geographically; on average, European wolves may weigh 38.5 kg (85 lb), North American wolves 36 kg (79 lb) and Indian and Arabian wolves 25 kg (55 lb). Females in any given wolf population typically weigh 5–10 lb (2.3–4.5 kg) less than males. Wolves weighing over 54 kg (119 lb) are uncommon, though exceptionally large individuals have been recorded in Alaska, Canada, and the forests of western Russia. The heaviest recorded gray wolf in North America was killed on 70 Mile River in east-central Alaska on July 12, 1939 and weighed 79.4 kg (175 lb).

Compared to its closest wild cousins (the coyote and golden jackal), the gray wolf is larger and heavier, with a broader snout, shorter ears, a shorter torso and longer tail. It is a slender, powerfully built animal with a large, deeply descending ribcage, a sloping back and a heavily muscled neck. The wolf's legs are moderately longer than those of other canids, which enables the animal to move swiftly, and allows it to overcome the deep snow that covers most of its geographical range. The ears are relatively small and triangular. Females tend to have narrower muzzles and foreheads, thinner necks, slightly shorter legs and less massive shoulders than males.

The gray wolf usually carries its head at the same level as the back, raising it only when alert. It usually travels at a loping pace, placing its paws one directly in front of the other. This gait can be maintained for hours at a rate of 8–9 km/h (5.0–5.6 mph), and allows the wolf to cover great distances. On bare paths, a wolf can quickly achieve speeds of 50–60 km/h (31–37 mph). The gray wolf has a running gait of 55–70 km/h (34–43 mph), can leap 5 m (16 ft) horizontally in a single bound, and can maintain rapid pursuit for at least 20 minutes.

Generally, wolves have a high heart weight of 0.93%-1.07% total body mass compared to the average mammal at 0.59% total body mass. Wolves have a decreased heart rate suggesting cardiac enlargement and hypertrophy. Tibetan gray wolves, which occupy territories up to 3,000 above sea level, have evolved hearts that withstand the low oxygen levels. Specifically, these wolves have a strong selection for RYR2, a gene that initiates cardiac excitation.

The gray wolf's head is large and heavy, with a wide forehead, strong jaws and a long, blunt muzzle. The skull averages 230–280 mm (9.1–11.0 in) in length, and 130–150 mm (5.1–5.9 in) wide. The teeth are heavy and large, being better suited to crushing bone than those of other extant canids, though not as specialised as those found in hyenas. Its molars have a flat chewing surface, but not to the same extent as the coyote, whose diet contains more vegetable matter. The gray wolf's jaws can exert a crushing pressure of perhaps 10,340 kPa (1,500 psi) compared to 5,200 kPa (750 psi) for a German shepherd. This force is sufficient to break open most bones. A study of the estimated bite force at the canine teeth of a large sample of living and fossil mammalian predators when adjusted for the body mass found that for placental mammals, the bite force at the canines (in Newtons/kilogram of body weight) was greatest in the extinct dire wolf (163), then followed among the extant canids by the four hypercarnivores that often prey on animals larger than themselves: the African hunting dog (142), the gray wolf (136), the dhole (112), and the dingo (108). A similar trend was found with the carnassial tooth bite force, but with the extinct dire wolf and gray wolf both measuring (141), then followed by the African hunting dog (136), the dhole (114), and the dingo (113).

The gray wolf has very dense and fluffy winter fur, with short underfur and long, coarse guard hairs. Most of the underfur and some of the guard hairs are shed in the spring and grow back in the autumn period. The longest hairs occur on the back, particularly on the front quarters and neck. Especially long hairs are on the shoulders, and almost form a crest on the upper part of the neck. The hairs on the cheeks are elongated and form tufts. The ears are covered in short hairs, which strongly project from the fur. Short, elastic and closely adjacent hairs are present on the limbs from the elbows down to the calcaneal tendons. The winter fur is highly resistant to cold; wolves in northern climates can rest comfortably in open areas at −40° by placing their muzzles between the rear legs and covering their faces with their tail. Wolf fur provides better insulation than dog fur, and does not collect ice when warm breath is condensed against it. In warm climates, the fur is coarser and scarcer than in northern wolves. Female wolves tend to have smoother furred limbs than males, and generally develop the smoothest overall coats as they age. Older wolves generally have more white hairs in the tip of the tail, along the nose and on the forehead. The winter fur is retained longest in lactating females, though with some hair loss around their nipples. Hair length on the middle of the back is 60–70 mm (2.4–2.8 in). Hair length of the guard hairs on the shoulders generally does not exceed 90 mm (3.5 in), but can reach 110–130 mm (4.3–5.1 in).

Coat color ranges from almost pure white through various shades of blond, cream, and ochre to grays, browns, and blacks, with variation in fur color tending to increase in higher latitudes. Differences in coat color between sexes are largely absent, though females may have redder tones. Black-colored wolves in North America inherited the Kballele responsible for melanism from past interbreeding with dogs, while the mutation was found to be naturally occurring in wolves from Iran. Black specimens are more common in North America than in Eurasia, with about half the wolves in Yellowstone National Park being black.

Sources and Credits

  1. (c) Aleksandar, some rights reserved (CC BY-SA), https://commons.wikimedia.org/wiki/File:Wolf_Tierpark_Hellabrunn-5.jpg
  2. (c) Aleksandar, some rights reserved (CC BY-SA), https://commons.wikimedia.org/wiki/File:Black_Canis_lupus.jpg
  3. (c) Klaus Rassinger, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Canis_lupus_05_MWNH_358.jpg
  4. (c) Klaus Rassinger, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Canis_lupus_02_MWNH_358.jpg
  5. (c) Klaus Rassinger, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Canis_lupus_01_MWNH_358.jpg
  6. (c) Klaus Rassinger, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Canis_lupus_03_MWNH_358.jpg
  7. (c) Klaus Rassinger, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Canis_lupus_04_MWNH_358.jpg
  8. (c) Didier Descouens, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Canis_lupus_Canine_perc%C3%A9e_MHNT_PRE_2010.0.12.2_Henri_Filhol.jpg
  9. (c) Squidocto, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:Canis-lupus-familiaris_track.jpg
  10. Unknown (Fish & Wildlife Service employee), no known copyright restrictions (public domain), http://commons.wikimedia.org/wiki/File:Canis_lupus_tracks.jpg
  11. (c) GlacierNPS, some rights reserved (CC BY), http://commons.wikimedia.org/wiki/File:Wolf_(Canis_lupus)_Tracks_(5634555361).jpg
  12. (c) Juan lacruz, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:20151229_111952_Excrementos_de_lobo.jpg
  13. (c) Juan lacruz, some rights reserved (CC BY-SA), http://commons.wikimedia.org/wiki/File:20151229_113609_Excrementos_de_lobo.jpg
  14. (c) Aleksandar, some rights reserved (CC BY-SA), https://www.flickr.com/photos/74743437@N00/9020105774
  15. Adapted by Aleksandar from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Wolf

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