Animal Field Guide

Gray Wolf

Canis lupus
(Canidae)

Montana Species of Concern
Global Rank: G4
State Rank: S3

Agency Status
USFWS: LE
USFS: ENDANGERED
BLM: SPECIAL STATUS

The gray wolf is the largest of the wild dogs. Adult male gray wolves in Montana weigh around 47 kilograms (104 pounds) and females weigh around 36 kilograms (80 pounds). Males average approximately 186 centimeters (73 inches) in length, while 180 centimeters (70 inches) is the average for females, with the tail compromising a little less than one-third of the total length in both sexes (Foresman 2001). About half the wolves in Montana are black with the other half gray. Both color phases may be found in a pack or in a litter of pups.

This species is not migratory but may move seasonally following migrating ungulates within its territory. Wolves also disperse widely. Male wolves in northwestern Montana can move an average of 113 km (70 miles) from their natal territory, and females 77 km (48 miles), before establishing a new territory or joining an existing pack (Boyd and Pletscher 1999). Dispersal peaks twice per year; first in January/February and second, in May/June (Boyd and Pletscher 1999). Some wolves are known to have dispersed up to 805 km (500 miles). Dispersal has been documented from Canada, Idaho and Wyoming to Montana. Montana wolves are also known to have dispersed to Canada, Idaho, and Wyoming.

The gray wolf exhibits no particular habitat preference except for the presence of native ungulates within its territory on a year round basis. In Minnesota and Wisconsin, wolves usually occur in areas with few roads and human disturbance (Thiel 1985, Mech et al. 1988, Mech 1989). Wolves establishing new packs in Montana have demonstrated greater tolerance of human presence and disturbance than previously thought characteristic of this species. They have established territories where prey are more abundant at lower elevations than expected, especially in winter (Montana Fish, Wildlife and Parks 2003).

Wolves are opportunistic carnivores that predominantly prey on large ungulates. Main prey items in Montana include deer, elk, and moose (Montana Fish, Wildlife and Parks 2003). Bison are also taken where the ranges of the 2 species overlap in and around Yellowstone National Park. Domestic livestock such as cattle and sheep are also preyed upon. Wolves may also eat alternative prey, such as rodents, vegetation and carrion. Wolves commonly hunt in packs, but lone wolves and pairs are able to kill prey as large as adult moose (Thurber and Peterson 1993).

In most areas, gray wolves are territorial throughout the year. Packs generally consist of a socially dominant pair, their offspring of the previous year, and new pups, although other breeding-age adults that may or may not be related to the alpha pair may also be present (Montana Fish, Wildlife and Parks 2003). More than 1 female in the pack can breed and give birth to pups. Pup survival when there are multiple litters is highly variable. Pack size varies and may include as few as 3 and as many as 37 (U.S. Fish and Wildlife Service et al. 2001). In the Glacier National Park area, packs generally include 8 to 12 individuals (Bangs and Fritts 1993). Packs share pup-rearing responsibilities including food provisioning and tending pups at the den or rendezvous sites (Montana Fish, Wildlife and Parks 2003). Pack activity is centered on the den site and nearby rendezvous sites from late April until September (Montana Fish, Wildlife and Parks 2003). Lone wolves may move through territories of established packs (Thurber and Peterson 1993). Pack territories are dynamic and change from year to year depending on prey availability, wolf populations, and relationships with neighboring packs.

Summer home ranges are smaller than winter ranges; the annual range may be up to several hundred square kilometers (km). In the Glacier National Park area, territory size averages around 780 square kilometers (301 square miles)(Bangs and Fritts 1993). Gray wolves may occasionally move several hundred kilometers, especially dispersing young. In Minnesota, most dispersers left when they were 11 to 12 months old; dispersal occurred mainly in February to April and October to November; 35% of known-age wolves remained in their natal territory for more than 2 years (Gese and Mech 1991). Average territory size in northwestern Montana was 220 square kilometers (185 square miles) but was highly variable (U.S. Fish and Wildlife Service et al. 2002). Average territory size for Yellowstone wolves was larger, averaging 891 square kilometers (344 square miles) (U.S. Fish and Wildlife Service et al. 2002).

Wolves are generally not instrumental in causing prey declines but their effect varies with other environmental circumstances. In Quebec, winter weather appeared to affect the deer population trend more than did wolf predation (Potvin et al. 1992). In south-central Alaska, wolf predation may have limited caribou recruitment (Bergerud and Ballard 1988), though winter starvation also was proposed as a significant population control. Gray wolves may take livestock as secondary prey when deer fawns (the primary summer prey) are less vulnerable due to better prenatal nutrition resulting from mild winter (USFWS 1990). In Minnesota, snow-induced changes in deer distribution and mobility resulted in changes in wolf movement patterns, sociality, and feeding behavior. When snow was shallow, wolves traveled farther and more often, spent less time with pack members, and used conifer cover less and killed fewer deer (Fuller 1991). Wolves have been implicated in declines in elk numbers around Yellowstone National Park. This relationship is still being studied in conjunction with other environmental factors.

In Montana, gray wolves breed in mid- to late February (Boyd et al. 1993), with gestation lasting about 63 days (Montana Fish, Wildlife and Parks 2003). A female can only give birth once a year. Breeding usually occurs between the dominant male and female in the pack and wolves normally do not breed until they are at least 22 months old (Mech 1970). Occasionally, more than 1 female in a pack may breed, resulting in more than 1 litter per pack (Ballard et al 1987). Young are typically born in late April in an underground burrow that has been abandoned by another mammal or dug by wolves. In northwestern Montana litter sizes range from 1 to 9 with a mean of 5.3 (Montana Fish, Wildlife and Parks 2003). Pups emerge from the den in about 3 weeks and are weaned in 50 days (also reported as 5 weeks). Young vacate the den when they are about 3 months old (Hoffmeister 1986) and move to a series of rendezvous sites throughout the pack's territory. The pups are large enough to travel with the entire pack by September. Some offspring remain with the pack; others disperse as they mature. Lone wolves generally do not successfully rear young, but they may if food is abundant (Boyd and Jimenez 1994).

Pup survival is variable and influenced by a number of factors including disease, predation, and nutrition. In Montana, pup mortality was most often attributed to human causes (Pletscher et al. 1997), but canine parvo virus was strongly suspected as a main factor in low pup survival in Yellowstone wolves in 1999 (Montana Fish, Wildlife and Parks 2003).

Although wolves dispersing from Canada were occasionally observed, gray wolves were essentially extirpated from Montana and the rest of the western United States in the early 1900s primarily due to conflicts with people. Wolves started recolonizing the area around Glacier National Park in 1979 and the first den documented in Montana in over 50 years was found in Glacier National Park in 1986. Wolves have since colonized much of northwestern Montana as a result of dispersal from Canada and Glacier National Park. In 1995 and 1996 wolves were reintroduced into Yellowstone National Park and central Idaho. Wolves resulting from these reintroductions have since expanded into areas in Montana near these reintroduction sites and continue to expand in numbers and distribution in Montana. Montana contains portions of 3 recovery zones. In the northwest Montana recovery area, wolves are classified as endangered. In the southern zones that include the areas around Yellowstone National Park (GreaterYellowstone recovery area) and the Bitterroot area of western Montana and central Idaho (central Idaho recovery area), wolves are classified as experimental, non-essential. As a prerequisite for delisting, the states of Montana, Idaho, and Wyoming need to complete management plans that maintain a recovered population and are federally approved. Gray wolves reached biological recovery goals for the Northern Rocky Mountains at the end of 2002, but the delisting process has been delayed due to the lack of an approved management plan from Wyoming. Montana and Idaho's plans were both approved by the U.S. Fish and Wildlife Service early in 2004. In 2005, Montana began implementing as much of its approved management plan as allowed by federal regulations through a cooperative agreement with the U.S. Fish and Wildlife Service. Montana Fish, Wildlife & Parks is the lead agency for wolf population monitoring, working with landowners to address adverse wolf-livstock interactions, doing public outreach, wolf research, and other activities. See the Montana Gray Wolf Conservation and Management Plan (Montana Fish, Wildlife and Parks 2003) for more detailed information. Montana Gray Wolf Conservation and Management Plan Full implementation of this plan will not take place until the U.S. Fish and Wildlife Service completes the delisting process.