Lupine Anatomy



Height and Weight

In general, Gray Wolves measure from 66 to 96 cm (26 to 38 inches) at the shoulder, and from 102 to 147 cm (40 to 58 inches) from head to the base of their tail. Tail length measures from 33 to 51 cm (13 to 20 inches). A Wolf's average weight ranges from 27 to 45 kilograms (60 to 100 pounds); however, some Wolves have been recorded in extremes of 18 to 80 kilograms (40 to 175 pounds). Female Wolves (called bitches) generally weigh 20% less than the males (called dogs).


Pelage

Wolves are covered in a moderate length pelt across most of their body. The color of their fur may range from pure black to pure white, with any tint or shade of gray, tan, cream, ochre (yellow-gold), sienna (reddish brown), and brown between. On Wolves having light and dark patterned fur, the markings tend to be lighter on the ventral (belly) side of the body and graduate to darker/longer/thicker fur on the dorsal (back) side.

The ears, forehead, and top of the muzzle are usually of a short/course/lighter fur, mingled of dark and/or mid pelage tones with the underside of the muzzle and throat being of lighter pelage tones. The legs and paws also have short/course/lighter fur. The tail is generally covered with a long/thick/bushy fur, the color scheme being similar to that of the rest of the Wolf; dark on top and lighter on the bottom. Light colored Wolves may even have a dark spot of fur covering the precaudal scent gland, also called the violet gland, at the top of their tail, about 10 cm (4 inches) from its base and on the tip.

In the wintertime a Wolf's pelt usually grows quite thick to keep the Wolf comfortable at cold temperatures. During this time the pelt fills in with a short, dense, under-growth of fine, or downy, light colored fur. This is sometimes called a "prime coat." In spring this fur is then shed, thinning the pelt dramatically to prevent the Wolf from over-heating as summer temperatures rise. Some call this thinning of the pelt "blowing" or "blowing-out" the coat.

Some Wolves, especially dark furred Wolves, have phases where their pelt lightens significantly during certain seasons or as they age. A black-phase Wolf starts life with a very dark or black pelt which may become lighter in the summer and then darken again in the winter. A dark or black-phase Wolf's fur also tends to lighten with age and may become light gray, or even white, as the Wolf reaches his or her senior years.

Wolves are generally born with dark or black fur which lightens as they mature. It is unlikely that Wolves are subject to albinism, as no living examples exist.


Eyes and Vision

Wolves are usually born with deep blue eyes which lighten and then gradually fade into the adult eye color over the next six to ten weeks. A mature Wolf's eyes are often amber/brown or gold, but also commonly come in hues of brown, gray, yellow, and green. It is interesting to note that puppies are born with blue eyes, while mature Wolves do not retain blue as an eye color. Huskies often have blue eyes, and because of this people think there must be blue eyed Wolves as well, but this isn't true. If you see a Wolf with blue eyes then he or she is likely a Wolf-hybrid and not a full-blooded Wolf.

A Wolf's eye sight is just about as good as that of a human being. However some experts believe that Wolves may be nearsighted because their eyes lack a foveal pit, an indentation in the retina which provides for focusing, especially on distant objects. Wolves have excellent peripheral vision and their eyes are optimized to detect motion. In addition, they have a very high ratio of rods (grayscale receptors) to cones (color receptors) in the retina; in fact, about 95% rods. This abundance of rods aids the Wolf in the ability to see at night. A Wolf's night vision is far superior to that of a human being.

Although little research has been done into a Wolf's ability to see color, it is believed that they may be partially color blind. Wolves have only red and blue photo receptors in their eyes, unlike humans, who have red, green, and blue photo receptors. Tests on domestic canines show that they may not be able to distinguish yellow from green or orange from red. Tests on Wolves, where red, blue, yellow, and green dyes were put onto clean snow, show that they often detect the red and yellow stains. This could be because they associate these colors with blood and urine and have little interest in the other colors. There is no conclusive evidence regarding the color vision abilities of Wolves, however. It is my personal belief that Wolves can see all of the colors, but only take an interest in those that might benefit them in some way.

Canines have a third eyelid (nictitans) which stretches across the eye and contains a gland which, along with glands in the ciliary body, acts to lubricate the eye. However, these tear glands excrete an oily substance rather than watery tears: Canines are not able to shed the moist tears of sorrow as humans do, but this doesn't mean they don't cry.


Ears and Hearing

A Wolf's ears are triangle shaped and rounded across the top; they are much broader and shorter than coyote or fox ears. Wolves tend to have shorter/darker fur on the backside of the ear, with a lighter, somewhat longer fur along the inside. Wolves are able fold their ears back against their head, move them side to side, and forward independently of each other. This range of motion assists the Wolf in detecting the direction of sound quite precisely. Wolves also use ear postures for communicating amongst themselves.

Hearing is a Wolf's second most developed sense. It is thought that domestic canines can hear sixteen times better than human beings. It is supposed that a Wolf's ability to hear is even better than this. Experts believe that Wolves may be able to hear frequencies far above the limits of human beings. The upper limit of human hearing is about 20 kHz, a Wolf's upper limit has been estimated at between 25 and 80 kHz. Wolves have been known to react to imitated Wolf howls from five kilometers (three miles) away. Some experts say that a Wolf can hear ten to sixteen kilometers (six to ten miles), depending on the density of trees and other obstacles between them and the source of the sound.


Nose, Tongue, Taste, and Smell

A Wolf's nose is composed dark or black, rubber-like, tissue at the end of the muzzle and above the lip, with a pair of nostrils leading to the nasal cavity which lie above the hard palate of the mouth. The nose is the only part of the canine body that "sweats," as there are no sweat glands in the skin. The nose gets wet and cold as the Wolf exercises in order to cool the blood flowing through the muzzle and facilitate a constant body temperature.

The sense of smell is a Wolf's most developed sense and greatest asset. A domestic canine's nasal cavity has about twenty-five times the number of olfactory receptors and fourteen times the scent receptive surface area of a human being. It has been suggested by experts that a Wolf may have twelve times the ability to detect odors of a domestic canine and a hundred times that ability of a human being.

The sense of smell plays a very important role in lupine life and society. Not only is it the means by which Wolves detect and locate pray, but it is instrumental in a variety of other tasks. A Wolf's body has scent glands (see the Scent Glands section) that tell a Wolf's health, mood, and identity to other Wolves. Upon meeting, Wolves will smell each other's muzzle, anus, and tail to make sure they know who the other Wolf is, and also learn details about health, mood, where the Wolf has been, and what she/he has been eating. Wolves use urination, called marking, to mark their territories so other Wolves may know they are crossing into another pack's land by smelling the marks.

A Wolf's tongue is long and quite soft. It is covered in hundreds of projections called papillae which aid in grooming and with tugging meat from bones. A Wolf also uses the tongue for licking up blood, drinking water, and during certain social rituals where tongue contact indicates respect and/or submissive behavior. The tongue is quite thick, but tapers to a thin tip that can be curved into a ladle-like form, making it especially useful for lapping up water.

It's difficult to know exactly what another animal is able to taste, but it is known that canines have taste receptors that permit them to know the sensations of sweet, salty, bitter, and acidic.


Teeth, Fangs, and Jaws

A Wolf has 42 teeth: the upper jaw has six incisors; for cutting flesh, two canines (also called fangs); for piercing into flesh and holding prey, eight premolars and four molars; for slicing and grinding. The lower jaw has six incisors, two canines, eight premolars, and six molars. The last premolars on the upper jaw and the first molars on the lower jaw are called the carnassial teeth; specialized for slicing through meat. The canines may reach a length of 5.7 centimeters (2.25 inches), which includes the area set within the jaws.

Experts have surmised that Wolves are capable of a jaw pressure of up to 105 kilograms per square centimeter (1,500 pounds per square inch). This is about twice the jaw pressure of a German shepherd.


Paws, Legs, and Movement

Wolves have long, strong legs and large paws; they are built for speed and agility. The forelegs appear pressed into the Wolf's narrow chest, with the elbow turned inward and the paws turned outward. This allows the Wolf's fore and hind legs to swing in a strait line so that the hind paw falls into the impression that the front paw left. Domestic canines generally leave the hind paw impression next to the forepaw impression. The Build of a Wolf's legs are ideal for fast, agile movement over all types of terrain, even deep snow. And the webbing between their toes makes Wolves excellent swimmers as well.

As with other canines, Wolves are digitigrade; meaning they bear their weight on their toes as they walk and not the entire sole of the foot. There are four toes on each hind paw, and five toes on each forepaw. However, one of the toes on the forepaw is used for clasping and doesn't touch the ground. Each toe has a calloused pad and a non-retractable claw. Also, each paw has a single large calloused heel pad. An adult Wolf's forepaw prints measure from about 11.4 to centimeters 12.7 (4 to 5 inches) in length and from about 9.5 to 11.4 centimeters (3 to 4 inches) in width, with their hind paws measuring 15 to 20% smaller then their forepaws.

The average gait of a Wolf is between 6.5 and 8 kilometers (4 and 5 miles) per hour. Wolves can maintain an average top speed of about 40 kilometers (25 miles) per hour over a distance of 3 kilometers (2 miles). A Wolf maintaining a speed of 56 kilometers (35 miles) per hour over 6 kilometers (4 miles) was reported by a Minnesota game warden in 1955. There have been other reports of Wolves running in excess of 56 kilometers (35 miles) miles per hour, but these are likely exceptional extremes. Wolves bound when they are in pursuit of large prey animals. L. David Mech reported that he witnessed Wolves bounding over 5 meters (16 feet) while in pursuit of moose. Wolves can keep up the chase for about twenty minutes, after which they tend to rest or sleep for at least ten to fifteen minutes before resuming activity.

It's not uncommon for a Wolf to travel 32 to 48 kilometers (20 to 30 miles) a day while hunting. Where food is scare Wolves have been recorded to have walked 190 kilometers (120 miles) searching for food in a single day. Wolves have a great capacity for long journeys. When dispersing from their pack, lone Wolves have been monitored traveling over 800 miles in search of new territory.


Anus, Genitals, and Tail

A Wolf's anal region not only serves the usual function of defecation, but also plays an important role in communication. To the lower left and right of the anal sphincter are the anal scent ducts. The exact purpose of these "scent glands" is uncertain, but it is theorized that they produce a potent scent unique to a given Wolf and are employed in scent marking and in greeting ceremonies for the purpose of establishing the identity and status of a given Wolf. In the communications section you will find more information on the role these glands play in lupine social life.

The male genitalia consist of a fur covered scrotum, composed of thin, dark colored skin. The scrotum surrounds the testicles and is designed to keep the testicles several degrees cooler than the Wolf's internal body temperature so that the sperm are not damaged by excessive warmth. From the scrotum extending along the lower belly is the prepuce, often called the sheath. The prepuce is a flap of fur covered flesh that sheaths and protects the penis. The penis is a soft fleshy organ which extends from the sheath as it pumps full of blood when the Wolf becomes sexually aroused. The penis contains a bone called the Baculum Bacula (OS penis), which aids in penetrating the female's vulva during copulation. When canines mate the
male's erection occurs after penetration, rather then before (to achieve) penetration as in humans. Toward the base of the penis is the bulbus glandis, also called the knot, which swells into the female's vagina to tie the male and female together during coitus. The knot prevents the mating pair from parting until after insemination has taken place. In addition to mating function and urination, the penis is also used to scent mark; it is believed that the urine contains a pheromone, or scent, unique to the individual Wolf and that other Wolves smelling this mark can easily identify the Wolf from whom it came from. Out of mating season a male Wolf's testicles tend to shrink, accompanied by the loss of sexual appetite.

The female genitalia are mostly internal. The external labium (lips) of the vulva occupies approximately the same physical location on the body as the scrotum would on a male. In the wintertime, when the female enters estrus, the vulva becomes hot and puffy (hence the term "in heat"). This puffy/swelling makes the female visually interesting to males, and along with the pheromones produced in the vagina, indicates when the bitch is physically ready to mate. The puffy vulva is also ideally shaped so that the tip of the male's penis can easily hook into its fold to be directed into the vagina during copulation. During copulation the male thrusts his penis into and out of the female's vagina while shifting his weight from one leg to the other in order to work his bulbus glandis into her. This locks the male's penis into the female's cervix, which undulates to stimulate his penis to erection. Erection expands the bulbus glandis and ties the two
Wolves together; thus coitus is achieved. Once coitus is achieved, the female's vaginal sphincter muscles tighten around the male's bulbus glandis to hold it firm as she pulls forward, triggering ejaculation of semen into the uterus. In the initial 30-50 seconds of the tie, the male deposits only clear semen until orgasm is achieved. During the initial 30 seconds or so of orgasm, a cloudy, somewhat thicker, sperm bearing semen is ejaculated; thus insemination is achieved. After insemination the semen returns to a clear state, but continues to pump forth until the end of the tie, which may last up to 35 minutes. Additional information about courtship and mating can be found in the procreation section.

A Wolf's tail measures from 33 to 51 cm (13 to 20 inches) and consists of long fur radiating away from it in all directions, but sloping toward the tip. Most Wolves have a dark spot of fur covering the precaudal scent gland, also called the violet gland, about 10 cm (4 inches) from the croup and on the tail's tip. The tail serves to protect the anus and genitals from insect bites as well as a device for communicating with other Wolves. The communications aspect of the Wolf's tail will be delved into in the section dealing with communication.


Scent Glands

There are various scent glands located across the Wolf's body which are used for communication of identity, mood, and health. Scent glands are located on the anus, the top of the tail, behind the ears, and on the cheek near the corner of the mouth. In addition, the penis and vagina also function as scent glands during urination marking.

Anal scent glands, located to the left and right and below the anal sphincter, produce a pungent oily pheromone that is excreted during bowel movements, thus scenting the Wolf's scat with his or her unique odor. The purpose for this is unknown, but it is believed that the anal scent glands play an important role in the identity of Wolves, for high ranking males often lift their tails during greeting ceremonies, whereby both Wolves sniff each other under their tails, before they accept each other. Submissive males and females of any rank usually do not greet this way, and will tuck their tail to avoid attempts to know them this way. The exception to this is when the dominant female enters estrus, at which time she will lift her tail to a ranking male, so that he may know she is receptive to mating.

Another major scent gland, called the precaudal gland or violet gland, is located near the top of the tail, about 10 cm (4 inches) down from the croup. Again the actual purpose of this gland is unknown, but it is believed that the oily bluish pheromone it produces may indicate a Wolf's mood or level of sexual receptivity during mating season.

There is little information available for the scent glands below the ears and on the cheeks, except that they are sniffed during greetings and sometimes nuzzled during active submission displays. See the communications section for more information on this topic.



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