Damage and Damage Identification

Adult gray wolf, Canis lupus

The ability of wolves to kill cattle, sheep, poultry, and other livestock is well documented (Young and Goldman 1944, Carbyn 1983, Fritts et al. 1992). From 1975 through 1986, an average of 21 farms out of 7,200 (with livestock) in the Minnesota wolf range suffered verified losses annually to wolves (Fritts et al. 1992). In more recent years, 50 to 60 farms annually have been affected by wolf depredations in Minnesota. Domestic dogs and cats 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 (up to 35) 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 (Roy and Dorrance 1976). 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 (8.1 to 9 kg) 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 (0.6 cm) in diameter while those of a coyote are about 1/8 inch (0.3 cm) 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 large tracks are present, especially in more populated areas. Large dogs usually injure and kill many 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 includes signs of a struggle and hemorrhaging beneath the skin in the throat, neck, back, or hindquarter area.

Figure 3. Gray wolf and coyote silhouettes and track measurements of each.

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 its rear foot. The front foot of the Alaskan subspecies is 4 to 5 inches (10.2 to 12.7 cm) long (without claws) and 3 3/4 to 5 inches (9.5 to 12.7 cm) wide; the rear foot is 3 3/4 to 4 3/4 inches (9.5 to 12.1 cm) long and 3 to 4 1/2 inches (7.6 to 11.4 cm) wide (Murie 1954) (Fig. 3). 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 and 38 inches (63.5 to 96.5 cm). When walking, wolves usually leave tracks in a straight line, with the rear foot prints overlapping 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 (droppings) 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. Scats 1 inch (2.5 cm) or larger in diameter are probably from wolves; smaller scats may be from wolves or coyotes. 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 fine 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 (Gauthier and The berge 1987). Studies in Minnesota (Mech and Karns 1977), Isle Royale (Peterson 1977), and Alaska (Gasaway et al. 1983, Ballard and Larsen 1987) indicate that predation by wolves, especially during severe winters, may bring about marked declines in ungulate populations. It appears that after ungulate populations reach low levels, wolves may exert long-term control over their prey populations and delay their increase.

Legal Status

All gray wolves in the contiguous 48 states are classified as “endangered” except for members of the Minnesota population, which are classified as “threatened.” The maximum penalty for illegally killing a wolf is imprisonment of not more than 1 year, a fine of not more than $20,000, or both. The classification of the wolf in Minnesota was changed from “endangered” to “threatened” in April 1978. This classification allows a variety of management options, including the killing of wolves that are preying on livestock by authorized federal or state personnel. In Canada and Alaska, gray wolves are considered both furbearers and game animals and are subject to sport harvest and control measures regulated by province or state agencies.

Red wolves are classified as “endangered” in the United States. This classification restricts control of red wolves to authorized federal or state damage control personnel, who may capture and relocate red wolves that are preying on livestock.

Economics of Damage and Control

Wolves can sometimes cause serious economic losses to individual livestock producers. Minnesota, Wisconsin, and Montana have established compensation programs to pay producers for damage caused by wolves. In recent years, $40,000 to $45,000 has been paid annually to Minnesota producers for verified claims of wolf damage. Control of depredating wolves is often economically feasible, but it can be time-consuming and labor intensive. If wolves can be trapped, snared, or shot at depredation sites, the cost is usually low.

Deer, moose, and other ungulates have great economic and aesthetic value, but wolves have strong public support. Thus, wolf control is often highly controversial. Where wolves are the dominant predator on an ungulate species and prey numbers are below carrying capacity, a significant reduction in wolf numbers can produce increases in the number of ungulate prey (Gasaway et. al. 1983, Gauthier and Theberge 1987) and therefore sometimes can be economically justified. When control programs are terminated, wolves may rapidly recover through immigration and reproduction (Ballard et al. 1987). Therefore, wolf control must be considered as an acceptable management option (Mech 1985).