Defenders' Experts
The Basics of Wolf Biology and Taxonomy
The gray wolf (Canis lupus) is the largest member of
the canid (dog) family in North America. The table below compares the size and
appearance of the gray wolf to the other canid species in the U.S.
| Gray
Wolf (Canis lupus) |
Red
Wolf (Canis rufus) |
Coyote (Canis latrans) |
Fox (Vulpes or Urocyon) |
|
| Size | 5-6 feet long from nose to tail | 3-4 feet long from nose to tail | 3-4 feet long from nose to tail | 3-3.5 feet long from nose to tail |
| Weight | 80-120 pounds | 40-80 pounds | 30-40 pounds | 12 pounds |
| Color | gray, tan, brown, black, or white | reddish brown, black, or gray | reddish brown, tan, or gray red-brown (red fox) | grizzled- gray (gray fox) |
| Eye color | Yellow, green, or brownish | Yellow, green, or brownish | Yellow to green | Yellow to brown |
Wolves are highly intelligent. Their acute hearing and exceptional sense of smell - up to 100 times more sensitive than that of humans - make them well-adapted to their surroundings and to finding food. Some researchers estimate that a wolf can run as fast as 40 miles an hour. Wolves have been known to travel 120 miles in a day, but they usually travel an average of 10 to 15 miles a day.
Pack Life
Wolves live, travel, and hunt in packs of four to seven animals, consisting of an alpha, or dominant pair, their pups, and several other subordinate or young animals. The alpha female and male are the pack leaders, tracking and hunting prey, choosing den sites, and establishing the pack's territory. The alpha pair mate in January or February and give birth in spring, after a gestation period of about 65 days. Litters can contain from one to nine pups, but usually consist of around six. Pups have blue eyes at birth and weigh about one pound. Their eyes open when they are about two weeks old, and a week later begin to walk and explore the area around the den. Pups romp and playfight with each other from a very young age. Scientists think that even these early encounters establish hierarchies that will help determine which members of the litter will grow up to be pack leaders. Wolf pups grow rapidly, reaching 20 pounds at two months and full size in a year. All adults share parental responsibilities for the pups. They feed the pups by regurgitating food for them from the time the pups are about four weeks old until they learn to hunt with the pack.
A wolf pup is the same size as an adult by the time he or she is about a year old, and is able to mate by about two years of age. Pups remain with their parents for at least the first year of their of their lives, while they learn to hunt. During their second year of life, when the parents are raising a new set of pups, young wolves can remain with the pack, or spend periods of time on their own. Frequently, they return in autumn to spend their second winter with the pack. By the time wolves are two years old, however, they leave the pack for good to find mates and territories of their own.
Not all the pups in a litter live to the age of dispersal, of course. Biologists have determined that only one or two of every five pups born live to the age of 10 months, and only about half of those remaining survive to the time when they would leave the pack and find their own mates. Adult wolves on the other hand, have fairly high rates of survival. A seven year old wolf is considered to be pretty old, and a maximum lifespan is about 16 years.
Communication
Wolves communicate through facial expressions and body postures, scent-marking, growls, barks, whimpers and howls. Howling can mean many things: a greeting, a rallying cry to gather the pack together or to get ready for a hunt, an advertisement of their presence to warn other wolves away from their territory, spontaneous play and bonding. There is no evidence, however, that wolves howl at the moon. Pups begin to howl at one month old. The howl of the wolf can be heard for up to six miles. When wolves in a pack communicate with each other, they use their entire bodies: expressions of the eyes and mouth, set of the ears, tail, head, and hackles, and general body posture combine to express excitement, anxiety, aggression, or acquiescence. Wolves also wrestle, rub cheeks and noses, nip, nuzzle, and lick each other. Wolves also leave "messages" for themselves and each other by urinating, defecating, or scratching the ground to leave scent marks. These marks can set the boundaries of territories, record trails, warn off other wolves, or help lone wolves find unoccupied territory. No one knows how wolves get all this information from smelling scent marks, but it is likely that wolves are very good at distinguishing between many similar odors.
Hunting
Wolves prey mainly on large hoofed mammals (known as ungulates) such as deer, elk, moose, caribou, bison, bighorn sheep and muskoxen. They also eat smaller prey such as snowshoe hare, beaver, rabbits, opossums and rodents. Although some wolves occasionally prey on livestock, wild prey are by far their preferred food source.
Wolves have several different methods of hunting, depending on the size of the prey. For little tidbits such as mice, an individual wolf will listen for the squeaking and rustling under the leaves, and then pounce with her front paws when she pinpoints the direction of the sound. They will also eat birds, especially when the birds are molting their feathers and cannot fly well. Individual wolves will also chase hares or follow beaver trails to try to catch the animal away from the water. When hunting deer, pack members frequently all participate in the locating and stalking of prey. After that, anywhere from one to all of the wolves will engage in the chase. Larger prey animals, such as moose, caribou, and elk, don't always run when they encounter a pack of wolves. If the prey animal stands its ground, the wolves will often approach cautiously or abandon their pursuit after a few moments. When a prey animal does flee, the pack of wolves will chase them. Most healthy ungulates are fast enough to outrun a pack of wolves. In fact, fewer than one out of ten attempts to chase moose actually end in a successful kill. If they start to fall behind, the pack will usually give up the chase. If the chosen prey is injured, weakened, or old, however, the wolves can usually catch up with them and attack. Contrary to many popular accounts, wolves rarely, if ever, engage in "hamstringing," or biting the tendons on the back of the leg. This practice is simply too dangerous for the wolf, because to bite the leg, the wolves risk getting kicked in the face by the animal's sharp hooves. Wolves tend to concentrate on the neck, shoulders, and sides instead.
Wolves' digestive systems operate somewhat differently than ours. They are adapted to process huge amounts of food at a time, then eat nothing for three days or more. Biologist David Mech witnessed a pack of 15 wolves kill a 600- pound moose and eat about half of it in an hour and a half, meat, bones, fur and all. This works out to about 20 pounds of food per wolf! Mech estimated that the wolves he witnessed in this encounter were about 85 pounds each, which means they each ate about 23% of their body weight. They don't do much chewing, mostly just tearing chunks off and swallowing them whole. After eating their fill, wolves will either spend a few hours relaxing and digesting, or return to the den to regurgitate food for the pups and other pack members who did not join in the hunt. A wolf's digestive system can handle a large amount of food quickly and efficiently, processing the meat and fat so thoroughly that only bones and fur are excreted in the scat.
Taxonomy and Evolution of the Gray Wolf
| The gray wolf is in: | Which includes: | And excludes: | |
| Kingdom | Animalia | All multicellular organisms that lack cell walls and cannot perform photosynthesis | Plants, Fungi, Protists,Bacteria |
| Phylum | Chordata | All animals that have a backbone or similar internal support | Invertebrates (insects, snails, starfish, etc.) |
| Class | Mammalia | All chordates that have fur and produce milk | Fish, Amphibians, Reptiles, Birds |
| Order | Carnivora | All mammals that mostly eat meat | Rodents, deer, primates, etc. |
| Family | Canidae | All carnivores that are dog-like, with 42 teeth, walk on their toes, and have long, bushy tails | Lions & tigers, bears, raccoons, weasels, etc. |
| Genus | Canis* | Wolves and coyotes | Foxes, bush dogs |
| Species | lupus* | Gray wolf | Canis latrans, the coyote Canis rufus, the red wolf |
| Subspecies | baileyi* lycaon* |
Mexican gray wolf Eastern timber wolf |
Gray wolves of other subspecies |
*The genus and species form the "scientific name" of the species and are always italicized or underlined. The genus name is capitalized, the species name is not. The subspecies name, when used, is lower case, italicized, and follows the species name, e.g. Canis lupus lycaon. The map on the following page shows the distribution of the two species and various subspecies of wolves in North America.
Scientists are not absolutely certain about the details of how and where the wolf evolved, but by examining fossil bones, especially skulls, of animals that lived millions of years ago, they have been able to form educated hypotheses about the ancestry of wolves and their relationships with other animals. Wolves and other predators probably evolved from a small meat-eating mammal that lived in the early Cenozoic Era, 65 million years ago. Specialized teeth for eating meat appeared about 55 million years ago in an animal called Miacis. It is likely that the dogs, cats, bears, weasels, raccoons and other carnivores all branched off from this line of primitive carnivore. A distinctively doglike mammal a little smaller than a fox, called Cynodictus, arose about 30 million years ago. Over the next 10 million years, this branch of the carnivore lineage developed a larger brain, longer legs, and the dewclaw, or reduced fifth toe that is visible in dogs. Wolves began to take on their distinctively large size about 15 million years ago, and looked like they do today by about 1 million years ago. Every breed of dog that we have today, from poodles to huskies, are descended from a small subspecies of wolf that was domesticated in China about 12,000 to 15,000 years ago.
The above information is taken from the Defenders of Wildlife's Wolf Pack Education Curriculum.
Wolf Fact Sheets
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