Canis lupus
(Gray Wolf)

Order: Carnivora
Order Description: Carnivores
Family: Canidae
Family Description: Wolfs, Coyotes, and Foxes

Gray wolves are the largest members of the canid family in North America. Males weigh between 45 and 175 pounds (20-78 kg) while females range between 40 and 120 pounds (18-52 kg). The largest of the reintroduced wolves in Yellowstone weighed 141 pounds. They are easily distinguished from coyotes by their large size, relatively shorter ears and broad snout. Unlike coyotes they hold their tail horizontally when running. They appear much “stockier” than coyotes. Their coloration is much more variable than coyotes, from the common grizzled, gray color to almost white to black. Their long, bushy tail is commonly black tipped. Total length is 40 to 80 ˝ inches (100-205 cm), and tail length is 14 to 20 inches (35-50 cm).

Historically gray wolves were found over most of North America, but intensive and systematic shooting and trapping by humans decimated their populations by the early 1900’s. Now they are found south of Canada only in northwestern Montana, central and northern Idaho and Yellowstone National Park as a result of reintroduction in 1995 and 1996, northeastern Minnesota, northern Wisconsin, Michigan's Upper Peninsula, and Cascade Mountains of Washington near the Canadian border at Ross Lake.

Wolves were once found throughout Idaho, but now they are restricted to forested areas and mountainous country in central and northern Idaho. They move over vast areas in forests, high mountain valleys and in other habitat where large ungulates, their primary prey, are present.

They prefer ungulates such as deer, elk and even bison, but they also eat beaver, snowshoe hare, rodents such as ground squirrels and mice, and carrionClick word for definition. In Yellowstone National Park it is not uncommon to observe wolves “mousing” in grassy meadows much like coyotes and red fox. Individuals may take livestock as secondary prey when ungulates are less vulnerable or available.

Wolves seem to require areas with low human population, low potential for human interactions, high prey densities, and secluded denning and rendezvous sites. These requirements restrict them to fairly large tracts of wilderness. They commonly hunt in packs that often consist of one family group of variable numbers, but up to 20 or more on rare occasions. There is a highly organized social structure in packs. The alpha male is dominant over the alpha female and other members of the pack, the alpha female is dominant over other females, and a dominance hierarchy exists among the subordinate members of the pack. The social structure results from strong bonding between the pups and the parents (usually just the alpha pair) and other members of the pack who all help care for and feed the pups. The social structure leads to cooperation during hunting and capturing prey. Wolf packs are territorial, marking their territory by urinating and defecatingClick word for definition, and their howls also help advertise their presence and location. Besides howling, they communicate with a diverse array of postures and even facial expressions. The pups, after emerging from the natal den site are usually moved to a rendevous site, often an open grassy area within their territory. Gradually, as the pups grow they are included in hunts and taught to hunt by adults in the pack. Their summer home range may be smaller than winter range; their annual range may reach several hundred km2. Individuals may occasionally move several hundred km, especially when dispersing. Because of their large range and territories, population densityClick word for definition is typically low. Prior to introduction in Idaho, where wolf activity was closely linked to seasonality of ungulate movements, population density of naturally occurring wolves was unknown, but was probably very sparse. The total population was estimated at 15 animals in early 1980's. In 1991-92, wolves were documented in Bear Valley (Valley Co.) and Kelly Creek drainage (Clearwater Co.). Then in 1995, 15 wolves were released along Middle Fork of Salmon River in the Frank Church River of No Return Wilderness; in 1996, 20 more wolves were released in same general area. Those wolves currently roam throughout central Idaho and adjacent areas of Montana. Their population is currently (late 2000) estimated to be in excess of 150 wolves. During 1995 and 1996, wolves were also reintroduced in Yellowstone National Park, and that population is currently (late 2000) estimated at close to 200 wolves. Because wolves prey on large ungulates, they are selective predators. They typically only prey on old, sick or young members of their prey population. In this sense, some biologists refer to their predator habits as having a “cleansing” effect on the prey population. Besides humans, wolf pups could be preyed on by bears, but their large size precludes them as targets by other predators. While they appear to be large and ferocious predators there have been very few documented instances of wolves attacking humans.

Wolves breed between January and March. The dominant male and female mate and rear 1 litterClick word for definition of 4 to 10 young (average 6-7) per year. In some instances more than one female in a pack mates with the dominant male. GestationClick word for definition lasts 63 days. Young are born in late April or early May. Pups are weanedClick word for definition in about 50 days (5 weeks has also been reported). Some offspring remain with the pack; others disperse as they mature. The den in which the pups are born is usually in a secluded, sheltered location, and it is often used for more than one year. Females stay with the young for the first month or two while other pack members bring food to her and her pups.

Status: Protected nongame species
Global Rank: G4
State Rank: S1

Important State References:
U.S. Fish and Wildlife Service. 1994. Final Environmental Impact Statement. The reintroduction of gray wolves to Yellowstone National Park and central Idaho. Helena, MT. 441pp.

Information written by Donald Streubel,© 2000
Photo from Yellowstone- National Park Service, Jan 2001.
Map image provided by Stephen Burton,© 2000
Design by Ean Harker 1999, 2000, 2001.