Anatomy and Physiology title

Size | Foot Structure and Speed | Colour | Teeth |Wolf Senses | Diseases | Longevity

The Gray Wolf is the largest member of the canid family. As we proceed, we will begin to study more about the anatomy and physiology of the wolves, starting with its size...



Size

Some myths and legends of old would have us believe that wolves typically weighs around 200lbs (91kg), ravening the countryside in search of choice virgins and lusty children, while ransacking villages. In fact, many people who have never seen a wolf in their lives before, firmly believed that wolves are enormous. It hardly makes a difference whether these people dwelt in the medieval period, or oddly enough in this era of information superhighway, the present.

Barry Lopez noted in his book, Of Wolves and Men, that even people who have considerable experience with wolves seem to want them to be bigger than it is. He illustrated an example in page 18, "A trapper in Minnesota, a man who had caught hundreds of wolves in his life, looked at one in a trap one day and judged its weight at eighty-five or ninety pounds. When it was weighed and found to be sixty-seven pounds, he became slightly indignant with the creature and said, 'He's got the frame to carry ninety pounds. Must be sick.'"

Wolf Skeleton
Wolf Skeleton
Source: The Wolf Almanac by Busch, Robert H., pg.22

Although smaller than legend, adult males from most areas range between 75-125lbs (34-57kg). Wolves in the norther portions of their range tend to be larger than their counterparts in the south. They range in size from about 45lbs from an adult Arabian wolf to well over 100lbs for a large timber wolf. In Alaska, where perhaps the biggest wolves are found, a wolf that weighs more than 120lbs (54.5kg) is uncommon.

In saying that, there are authenticated records of male wolves weighing as much as 175lbs (79kg). This animal was killed on 70 Mile River in extreme east central Alaska by a government hunter on July 12, 1939. A Canadian park ranger killed a 172lbs (78kg) animal in Jasper National Park in 1945. The heaviest recent wolf on record is a 122lbs (55kg) male captured for radio-collaring in Montana in 1994. Males are typically between 5-10lbs (2.2-4.5kg) heavier than females.

An average weight for a North American grey wolf would be 80lbs (36kg), less in southern Canada, more in the north. The little red wolf of the southeastern United States rarely exceeds 65lbs (29.5kg) while the average weight of 28 wolves killed in the 1970s in Mexico was only 70lbs (32kg). A mature European wolf might weigh 85lbs (39kg). Wolves in the Punjab in India and on the Arabian Peninsula might average 55lbs (25kg).

Measured from tip to tail, an adult grey wolf is about as long as an adult person is tall, or between 50-70 inches (1.3-1.8 metres), of which 1/4 is tail length, and stand around 3/4 of a meter (2 1/2 feet) at the shoulder.

Compared to dogs of same size, wolves chest are much narrower. Their legs are also longer in proportion to their body weight. Their legs are also longer in proportion to their body weight than most dogs. Because of its narrower chest, the wolf's left and right foot track are closer together than those of dogs.

As large as wolves are, they usually appear to be much larger because of their long hiar. In their winter coat, the hair on their back and sides averages 2-2.5 inches (5-6.3cm) in length. Starting at the base of the neck, the wolf has a teardrop-shaped mane of hair that elongates into just a crest down the spine towards the tail. Over the shoulders, the mane is about 6 inches (15.2cm) wide. The hair in the mane are are 4-5 inches (10-12.7cm) long and are attached to erectorpili muscles, which allows their hair to stand on end, making the wolf appear much larger than it is actually is.

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Foot Structure & Speed

Wolf tracks are very similar to those of the domestic dog, consisting of four pad prints plus claw marks. The wrist bone of the wolf are fused together for extra strength. When closed, the toes are rugged and strong. Splaying the toes allows the wolf to grip on slippery, uneven and steep surfaces.

All members of the canine and feline family are digitigrade or walking just upon their tiptoes. Unless a wolf is lying down, the heel of each foot does not come in contact with the ground. the front feet of the wolf are exceptionally large. This is of great advantage to the wolf when it runs upon snow as it allows greater weight distribution and more support to prevent the animal from sinking in as deeply when the snow is soft.

Wolf Paw
Footprint of a 3-year-old Alaskan timber wolf, actual size.
Source: Of Wolves and Men by Lopez, Barry., pg.20

The foreprint of a wolf varies from 4 1/2 to 5 inhces in length and 3 3/4 to 4 1/2 inches in width. The back feet are smaller, leaving prints about 3 3/4 inches long and 3 1/4 inches wide. Tracks in soft medium such as sand or mud often appear larger and tracks in snow melted by the sun often appear huge. The small 'thumbs' on the front feet do not leave a mark, since they are elevated above the level of the remaining claws.

Depending on the gait, the distance between the tracks of the hind feet and those of the front feet varies from 25 to 38 inches.

A large domestic dog has a very similar track, but experienced trackers use two clues to distinguish them from wild prints. In dogs, the two outside toes often points slightly outward from the heel, but in wolves, the outer toes point straight ahead. In addition, the tracks of a wolf often lie more in a straight line than those of a dog, since dogs tend to wander more to each side of a straight line.

Wolves are agile creatures but not as deft and quick as coyotes. Red wolves move in a more delicate manner than grey wolves, appearing to put less weight on the foot. Wolves spend an average of eight to ten hours out of every twenty-four on the move, mostly the crespuslar hours. They travel great distances and ave tremendous stamina. A Finnish biologist reported one pack moved 125 miles in a day. The naturalist Adolph Murie watched a pack in Alaska make a regular daily round of about 40miles in search of food while the female was denning. Tundra wolves may run for 5-6 miles behind caribou before accelerating to attack.

Wolves walk with a trotting pace, and leave a single line of pawprints. Other wolves walk along the leader's tracks in single file. Wolves are good runners, and with their loping style of running over long distances, managing speeds up to 45km/h (28mph) in shorter bursts.

The wolf has five toes on each forefoot, but only four are actually needed. The fifth toe, corresponding to our thumb, has regressed. It is now found up on the middle of the foot and is known as the dewclaw. There are just four toes on each of the hind feet. Each toe pad is surrounded by stiff, bristly hair, which acts as insulation and also provides a better grip on slippery ice surfaces. The claws are strong and blunt because the tips are worn off by constant contact to the ground. These are used for digging and in gripping the earth while running, not for seizing prey.

Wolves walk, trot, lope, or gallop. Their legs are long, and they walk at about 4 miles (6.4km) per hour. Their usual mode of travel is to trot, which they do at various speeds, generally between 8 to 10 miles (12.8-16km) per hour. Wolves can keep this pace for hours on end and have been known to cover 60 miles (64km) in a single night. They have been clocked at speeds of over 40 miles (64km) per hour dor a distance of several miles.

Wolves do not run at full speed until they get as close to their prey as possible. At that point, they make a high-speed chase to test the animal.

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Colour

The wolf coat consist of two layers; a soft, light coloured, dense underfur that lies beneath a covering of long guard hairs which shed moisture and keep the underfur dry. Wolves range from all shades of grey, blond, ochre, brown to pure white or solid black. Amongs the more striking are the slate blue coats of some arctic wolves. The tip of a wolf's tail, however, is often coloured black.

Both the red wolf and Abyssian wolf have reddish coats. The red wolf, which inhabits hot, humid areas on the Gulf Coast, has a short, coarse coat and large, pointed ears in contrast to the short, rounded ears of tundra wolves. Short ears are less sensitive to the cold while long ears can dissipate body heat more efficiently.

Barry Lopez (1978) noted the great variation of coat colours in the Arctic region: "The great variety in pelage... among wolves in a single area is attested to by the number of words people use to describe local wolf coloration. 'Peach,' 'yellow,' 'orange,' 'tan,' and 'rusty' were all words I heard used in the Arctic. One eskimo remembered trapping a spotted wolf, a black with white patches in its coat, in 1968 in the Brooks Range."

Stanley Young (1994) further added, "The color of North American wolves... varies greatly, so much so that it is relatively unimportant for the scientific description of the animals."

White phase female with pup
White Phase Female Wolf with Sooty Brown Pup
Source: The Wolf Almanac, by Busch, Robert H.

As a general rule of thumb, most wolves in North America tend to be a grizzled grey-brown colour, though it is not unusual to have a variation of colours within a litter. These litter mates usually have the same quality of fur. The colour of newborns are said to be sooty brown, except in the Arctic where the pelage is either light blue or dull slate.

Variations in colour within a pack is also commonplace. L. David Mech noted of "a pack with three gray wolves, one black and one white." Dark-phase wolves often comprises a third of wolf populations found in southern Canada and Minnesota but mostly, greys predominate, hence the common name. But even then, the coats usually have a lot of base yellow interspersed between the salt-and-pepper gret and black hairs.

Many of the wolves in Canada's high Arctic are a creamy-white colour. These white hair shafts have more air pockets than colouration pigment, and therefore provide better insulation to the canids. White wolves have been reported as far south as Minnesota in recent years, but in the past they appear to have been quite common in the Great Plains. The Lewis and Clark expedition, mountain men, explorers and immigrants reported large numbers of very light wolves in the early 1800s.

The colour of the coat apparently has no camouflage function, as black wolves are commonly found on the tundra and white wolves stand out against the black soils of central Russia.

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Bleached Skull
Bleached Wolf Skull
Source: Wolves by Savage, Candace., pg.27

Teeth

The wolf has extremely strong jaws. According to Barry Lopez, the jaws of a wolf have a "crushing pressure of perhaps 1,500lbs/in compared to 750lbs/in for a German shepherd." No longer needing to bring down big prey, dogs developed skulls and teeth that were smaller, relative to their overall size, than a wolf's.

As noted in the summary found in the Ecology of the Wolf, the wolf has a dental formula of 3/3, 1/1, 4/4, 2/3, for a total of 42 teeth. Humans on the other hand has a dental formula of 2/2, 1/1, 2/2, 3/3, for a total of 32 teeth.

The need to make room for the sheer number of teeth, and to deploy them usefully probably account for the animal's characteristic long stout. A wolf's upper jaw is equiped with six incisors, two canine teeth, eight premolars, and four molars, while the lower jaw has six incisors, two canines, eight premolars, and six molars.

Wolf Dentition
Wolf Dentition
Adapted From: The Wolf Almanac by Busch, Robert H., pg.27

In incisor as seen in the picture above are used to cut flesh from prey. The long canines, which may reach up to 2 inches in length, tearing into flesh to grasp or hold prey. They are the functional equivalent of talons and permit a wolf to pierce through tough hides and thick hair and... to hang on for dear life...

Premolars and molars grind and slice meat. The high-ridged carnassial teeth, the last premolars in the upper jaw, and the first molars in the lower jaw are used for scissoring off chunks of meat to be swallowed. Wolves seldom chew their food. It is said by Candace Savage in Wolves that "the carnassial was one of the reasons that the modern line of carnivoires has the means to survive". And finally, the last molars are used to grind and pulverised food prior to digestion.

Barry Lopez noted that "the animal can develop a crushing pressure of perhaps, 1,500 lbs/in² compared to 750 lbs/in² for a German Shepherd. This is enough to break open most of the bones the wolf encounters to get at the marrow. Stanley Young further wrote that, "A wolf can snap off the tail of a yearling, a full-grown cow, or steer with the cleanness of cut as that of a scythe on maturing hay."

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Wolf Senses

Most wolf biologists agree that the most acute of a wolf's senses is that of smell. The sense of smell in the wolf is highly developed, as would be expected in an animal possessing numerous scent glands. The surface area receptive to smell in the wolf's nose is fourteen times that of human nose, although the degree of sensitivity to smell is not directly corelative to the surface area. In The Wolf: The Ecology and Behavior of an Endangered Species, L. David Mech wrote that "Researchers estimate that this ability is up to one hundred times more sensitive than that of man." Research has shown that wolves have been able to detect their prey at distances of up to 1.75 miles (3km). The wolves usually travel until they encounter the scent of some prey species ahead of them. They then move directly toward their prey in and effort to capture it. Wolves also use scent to mark their territory and to identify individuals.

Next to smell, the sense of hearing is the most acute of the wolf's sense. Barry Lopez, in Of Wolves and Men, states that "wolves can hear well up to a frequency of 25 kHz." Other researchers believe that the actual maximum frequency detected by wolves are much higher, perhaps even up to 80 kHz. Humans, by contrast, can only hear up to 20 kHz. While a dog's hearing is about 16 times better than ours, the wolves' hearing is much more acute than that. L. David Mech furthermore stressed that "wolves can hear as far as six miles away in the forest and ten miles away on the open tundra" When wolves howl, other wolves can hear the howling over an area of up to 120 square miles or 300 square kilometres on a calm night.

Wolves also have a keen eyesight and are quick to detect the slightest movement of anything in front of them. Like many major predators, the wolves' eyes are on the front of their heads, and they have probably less a little less than 180-degrees vision, unlike their prey species, which normally can see over 300 degrees of a circle. However, because of how their eyes are shaped, wolves are unable to focus sharply at an object at a great distance; since they are quite near-sighted, they would need to depend on their other more acute senses. R.D Lawrence stated in In Praise of Wolves, "they can see details clearly up to a distance of about 75 feet". The wolf also possess a night vision far superior than a man's. A high proportion of rods to cones in the retina is one measurement of strong night vision, and canines have almost 95% rods.

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Diseases

Wolves are susceptible to more than a hundred diseases and parasites, including various protozoa, roundworms, tapeworms, flatworms, mange, mites, ticks, fleas, distemper, cataracts, oral papillomatosis, tularemia, trichnosis, bovine tuberculosis, encephalitis, arthritis, brucellosis, cancers, rickets, pneumonia, Lyme disease, and many other ailments.

External parasites such as flies, ticks, fleas, and mites tend to be less of a problem in cold northern regions. The most common wolf afflictions are mange, caused by tiny mites, and tapeworms, ingested by wolves from their ungulate prey. Distemper is sometimes seen in wolves that have been in contact with domestic dogs.

Contrary to popular myths, rabies is very rare in the modern wolf. This was not the case a century ago, when Native Americans and explorers often reported encountering rabid wolves. Wolves however are not a primary vector of rabies in North America, usually contracting the disease from foxes and skunks. Rabies used to be very common in Europe during the Middle Ages, a period that spawned many of the myths surrounding the wolf. Rabies in wolves still occurs sporadically in Europe and in Asia.

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Mexican Pup
A Mexican wolf pup hiding in thick vegetation.
Photo © Landis, Dan. Wild Canid Survival and Research Center
Source From: The Wolf Almanac by Busch, Robert H.,

Longevity

Disease, parasites, and injuries take a heavy tool and hard winters and food shortages shorten the lives of many wolves, especially pups and subordinate pack members, however, the only true enemy of the wolf is man. A large percentage of wolf mortality has been caused by human activities.

Technically, a wild wolf can live up to 15-16 years if it survives the threat of human hunters, starvation, and aggression though in reality, its lifespan is much shorter. In The Way of the Wolf, L. David Mech stated, "Probably most wild wolves die before the reach five years of age." This is borne out by numerous field studies. In one Minnesota study of 165 wolves, only ten lived beyond nine years of age while another study in the same state noted that of the 55 wolves studied, only six lived beyond nine years, one reached 13, and the rest all died before the age of eight years. In captivity, wolves often live to 13-14 years of age, and occassionally older. The record age for a captive wolf appears to be 17.

Older wolves that can no longer hunt effectively may become the lowest ranking pack member, trailing behind and living off the remains of kills; or the others may allow it to go on travelling and feeding with them. If it was a former alpha animal, then how it is treated in old age may depend on how it has treated its packmates when it was in command.



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