Two species of wolves occur in North America, gray wolves and red wolves. The common names are misleading since individuals of both species vary in color from grizzled gray to rusty brown to black. Some gray wolves are even white. The largest subspecies of the gray wolf are found in Alaska and the northwest Territories of Canada. Adult male gray wolves typically weight 80-120 pounds and adult females 70-90 pounds. Although males rarely exceed 120 pounds and females 100 pounds, some individuals may weigh much more. Gray wolves vary in length from about 4.5 feet to 6.5 feet from nose to tip of tail and stand 26 to 36 inches high at the shoulders.
Red wolves are intermediate in size between gray wolves and coyotes. Typical red wolves weight 45 to 65 pounds. Total length ranges from about 4.4 to 5.4 feet. Wherever wolves occur, their howls may be heard. The howl of a wolf carries for miles on a still night. Both gray wolves and red wolves respond to loud imitations of their howl or to sirens.
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General Biology, Reproduction, and Behavior
Gray wolves are highly social, often living in packs of two to eight or more individuals. A pack consists of an adult breeding pair, young of the year, and offspring one or more years old from previous litters that remain with the pack. The pack structure of gray wolves increases the efficiency of wolves in killing large prey. Red wolves may be less social than gray wolves, although red wolves appear to maintain a group social structure throughout the year.
Each wolf pack has a home range or territory that it defends against intruding wolves. Packs maintain their territories by scent marking and howling. On the tundra, packs of gray wolves may have home ranges approaching 1,200 square miles. In forested areas, ranges are much smaller, encompassing 40 to 120 square miles. Some wolves leave their pack and territory and become lone wolves, drifting around until they find a mate and a vacant area in which to start their own pack, or wandering over large areas without settling. Extreme movements, of 180 to 551 miles have been reported. These movements were probably of dispersing wolves, The home ranges of red wolves are generally smaller than those of gray wolves. Red wolf home ranges averaged 27.3 square miles in southern Texas.
Wild gray wolves usually are sexually mature at 22 months of age. Breeding usually takes place from early February through March, although it has been reported as early as January and as late as April. Pups are born 60 to 63 days after conception, usually during April or May. Most litters contain 4 to 7 young.
Courtship is an intimate part of social life in the pack. Mating usually occurs only between the dominant male and female of the pack. Thus, only 1 litter will be produced by a pack during a breeding season. All pack members aid in rearing the pups.
Dominance is established within days after gray wolf pups are born. As pups mature, they may disperse or maintain close social contact with parents and other relatives and remain members of the pack.
Little is known about reproduction in red wolves, but it appears to be similar to that of gray wolves. Red wolves may breed from late December to early March. Usually 6 to 8 pups are produced.
Damage and Damage Identification
The ability of wolves to kill cattle, sheep, poultry, and other livestock is well documented. From 1975 through 1986 an average of 21 farms out of 7,200 in the Minnesota wolf range suffered verified losses annually to wolves. In more recent years, 50 to 60 farms annually have been affected by wolf depredations in Minnesota. Domestic dogs and cars are also occasionally killed and eaten by gray wolves.
In many instances, wolves live around livestock without causing damage or causing only occasional damage. In other instances, wolves prey on livestock and cause significant, chronic losses at individual operations. In Minnesota, wolf depredation on livestock is seasonal, most losses occurring between April and October, when livestock are on summer pastures. Livestock are confined to barnyards in the winter months, and therefore are less susceptible to predation.
Cattle, especially calves, are the most common livestock taken. Wolves are capable of killing adult cattle but seem less inclined to do so if calves are available. Attacks usually involve only one or two cattle per event. Depredation on sheep or poultry often involves surplus killing. In Minnesota, wolf attacks on sheep may leave several individuals killed or injured per night. Attacks on flocks of domestic turkeys in Minnesota have resulted in nightly losses of 50 to 200 turkeys.
Wolf attacks on livestock are similar to attacks on wild ungulates. A wolf chases its prey, lunging and biting at the hindquarters and flanks. Attacks on large calves, adult cattle, or horses are characterized by bites and large ragged wounds on the hindquarters, flanks and sometimes the upper shoulders. When the prey is badly wounded and falls, a wolf will try to disembowel the animal. Attacks on young calves or sheep are characterized by bites on the throat, head, neck, back or hind legs.
Wolves usually begin feeding on livestock by eating the viscera and hindquarters. Much of the carcass may be eaten, and large bones chewed and broken. The carcass is usually torn apart and scattered with subsequent feedings. A wolf can eat 18 to 20 pounds of meat in a short period. Large livestock killed by wolves are consumed at the kill site. Smaller livestock may be consumed at the kill site in one or two nights or they may be carried or dragged a short distance from the kill site. Wolves may carry parts of livestock carcasses back to a den or rendezvous sites. Wolves may also carry off and bury parts of carcasses.
Wolves and coyotes may show similar killing and feeding patterns on small livestock. Where the livestock has been bitten in the throat, the area should be skinned out so that the size and spacing of the tooth holes can be examined. The canine tooth holes of a wolf are about 1/4 inch while those of a coyote are about 1/8 inch in diameter. Wolves usually do not readjust their grip in the throat area as coyotes sometimes do; thus, a single set of large tooth holes in the throat area is typical of wolf depredation. Coyotes will more often leave multiple tooth holes in the throat area.
Attacks on livestock by dogs may be confused with wolf depredation if the large tracks are present, especially in more populated areas. Large dogs usually injure and kill may animals. Some dogs may have a very precise technique of killing, but most leave several mutilated livestock. Unless they are feral, they seldom feed on the livestock they have killed.
Wolves are attracted to and will scavenge the remains of livestock that have died of natural causes. Dead livestock in a pasture or on range land will attract wolves and increase their activity in an area. It is important to distinguish between predation and scavenging. Evidence of predation included signs of a struggle and hemorrhaging beneath the skin in the throat, neck, back or hindquarter area.
Tracks left by wolves at kill sites are easily distinguishable from those of most other predators except large dogs. wolf tracks are similar to coyote tracks but are much larger and reveal a longer stride. A wolf’s front foot is broader and usually slightly longer than is rear foot. Track measurements of the eastern subspecies of gray wolf found in Minnesota and Wisconsin are slightly smaller. The distance between rear and front foot tracks of a wolf walking or trotting on level ground varies between 25 to 38 inches. When walking, wolves usually leave tracks in a straight line, with the rear foot prints overlapping in the front foot prints. In deep snow, wolves exhibit a single file pattern of tracks, with following wolves stepping in the tracks of the leading wolf.
Wolf tracks are similar to the tracks of some large breeds of dogs but are generally larger and more elongated with broader toe pads and a larger heel pad. Dog tracks are rounder than wolf tracks, and the stride is shorter. When walking, dogs leave a pattern of tracks that looks straddle legged, with the rear prints tending not to overlap the front prints. Their tracks appear to wander, in contrast to the straight line pattern of wolf tracks.
Scats left in the vicinity of a kill site or pasture may be useful in determining wolf depredation. Wolf scats are usually wider and longer than coyote scats. Wolf scats frequently contain large amounts of hair and bone fragments. An analysis of the hair contained in scats may indicate possible livestock depredation. Since wolves feed primarily on big game, their scats are not as likely to contain the find fur or the small bones and teeth that are often found in coyote scats.
During hard winters, gray wolves may contribute to the decline of populations of deer, moose, and caribou in northern areas.