Montana Field Guide

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 2012). About half the Gray 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. Gray Wolves also disperse widely. Males 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 Gray Wolves are known to have dispersed up to 805 km (500 miles). Dispersal has been documented from Canada, Idaho and Wyoming to Montana. Montana Gray 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, Gray Wolves usually occur in areas with few roads and human disturbance (Thiel 1985, Mech et al. 1988, Mech 1989). Gray 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 (MTFWP 2003).

Gray Wolves are opportunistic carnivores that predominantly prey on large ungulates. Main prey items in Montana include deer, Elk, and Moose (MTFWP 2003). Bison are also taken where the ranges of the two species overlap in and around Yellowstone National Park. Domestic livestock such as cattle and sheep are also preyed upon. Gray Wolves may also eat alternative prey, such as rodents, vegetation and carrion. Gray Wolves commonly hunt in packs, but lone animals 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 (MTFWP 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 (USFWS 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 (MTFWP 2003). Pack activity is centered on the den site and nearby rendezvous sites from late April until September (MTFWP 2003). Lone Gray 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, Gray 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 Gray 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 (USFWS et al. 2002). Average territory size for Yellowstone Gray Wolves was larger, averaging 891 square kilometers (344 square miles) (USFWS et al. 2002).

Gray 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 Gray Wolf predation (Potvin et al. 1992). In south-central Alaska, Gray 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 Gray Wolf movement patterns, sociality, and feeding behavior. When snow was shallow, Gray Wolves traveled farther and more often, spent less time with pack members, and used conifer cover less and killed fewer deer (Fuller 1991). Gray 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 (MTFWP 2003). A female can only give birth once a year. Breeding usually occurs between the dominant male and female in the pack and Gray 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 Gray Wolves. In northwestern Montana litter sizes range from 1 to 9 with a mean of 5.3 (MTFWP 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 Gray 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 Gray Wolves in 1999 (MTFWP 2003).

Although Gray Wolves dispersing from Canada were occasionally observed, they were essentially extirpated from Montana and the rest of the western United States in the early 1900s primarily due to conflicts with people. As a result, they were listed as Endangered under the Endangered Species Act in 1967 (32 FR 4001). Gray 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. In 1995 and 1996 Gray Wolves were reintroduced into Yellowstone National Park and central Idaho. Wolves resulting from these reintroductions and those dispersing naturally from northwestern Montana and Canada have now colonized most of western Montana. Gray wolves reached biological recovery goals for the Northern Rocky Mountains at the end of 2002 and were delisted in May of 2009 (74 FR 15123 15188). However, they were relisted as Endangered/Experimental Nonessential on August 5, 2010 by federal court order. Then, on May 5, 2011, they were again removed from the Endangered Species Act by the Secretary of the Interior at the direction of the President of the United States and Congress under a rider associated with the Department of Defense and Full-Year Appropriations Act of 2011 (76 FR 25590-25592).

Montana Fish, Wildlife and Parks is the lead agency for Gray Wolves, including population monitoring, resolving wolf-livestock conflicts, research, and public outreach. Federal regulations continue to guide Montana Fish, Wildlife, and Parks management practices. You can access a variety of detailed information on Gray Wolves in Montana from the Montana Fish, Wildlife, and Park's Wolf Program website