Problems with Wolves
Last Update/Review: May 27, 2002
The carnivorous nature of wolves creates two major areas of conflict for Albertans. Predation of livestock costs ranchers time and money; and wolf kills of wild ungulates reduce hunters' harvests.
Predation of Livestock
Where livestock are grazed in wolf country, losses are inevitable. In western Canada, depredations occurred as early as 1841 at Fort Vancouver, and in 1857 at Fort Carlton on the North Saskatchewan River. In Alberta, losses to wolves followed the first cattle drive from Montana, at least as early as the late 1870s.
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Carbyn photo |
Wolf predation is an important limiting factor to bison in Wood Buffalo National Park. Working in the park in the early 1950s, Bill Fuller of the Canadian Wildlife Service observed that predation was most severe on very old animals, calves and those bison with tuberculosis or other handicaps. Fuller considered the removal of bison with advanced tuberculosis by wolves to be a service in herd sanitation. |
Today, wolf predation of livestock occurs along the forest-agricultural fringe, which in Alberta is more extensive than in any other province. Grazing reserves or leased pastures located within forested public land may have severe problems when wolves are abundant. Factors that influence the wolf-livestock issue include the numbers of livestock grazed and the care put into their supervision. Also important are the status of the local wolf population and the relative abundance of wild prey. Complaints involving wolf predation of livestock have been common in Alberta since 1972.
The following statistics provide an understanding of the extent of this wolf problem in Alberta. From 1972 to 1990, over 2800 complaints were reported to wildlife management authorities, an average of 160 per year. About 70 percent of these complaints involved claims of harassment, injury to, or killing of livestock and pets. Cattle composed about 73 percent of the livestock reports; dogs — 7 percent, horses — 6 percent, sheep — 5 percent, bison — 2 percent, poultry — 2 percent, goats — 1 percent, and other animals — 4 percent.
The Government of Alberta investigated wolf predation of cattle on remote pastures near the Simonette River during 1975-1981. Cattle were counted, classified by sex and age, and monitored for behavior and losses; and wolves were captured, radio-collared and their kills recorded. Although wild ungulates, especially moose, constituted the bulk of the year-round diet of wolves, cattle remains (hair) occurred in 20 percent of 245 summer wolf scats. Four out of every 10 cattle that died from known causes, were killed by wolves, but wolves mauled three for every one killed. Removal of most of the wolves during two winters reduced cattle mortalities. The investigators concluded that wolves were responsible for about 50 percent of the cattle losses on the remote area.
The Simonette River studies provided the opportunity for cattlemen, wildlife researchers and resource managers to cooperatively define the wolf-livestock problem at the field level. As a result of the research, government could better appreciate the extent of such predation. The study also evaluated the effectiveness of the province's control program and had implications for overall wolf management in agricultural areas.
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Carbyn photo |
Predation of UngulatesStudies of wolves and their food habits have provided conclusive evidence that wolves depend primarily on hoofed mammals for their sustenance. During winter, the wolf's diet is overwhelmingly composed of these large mammals, and even in summer, ungulates represent the bulk of the biomass consumed by most wolves. In Alberta, ungulate prey include moose, white-tailed deer, mule deer, elk, caribou, bison, bighorn sheep, feral horse, and occasionally, mountain goat. Beaver can be an important prey species during the ice-free season, and snowshoe hares can be locally important during cyclic highs. |
The frequency with which wolves kill ungulates has been determined in several study areas in North America by aerial observation or tracking, especially during winter when kills are more easily discovered. Kill rates, or the number of days between kills, are influenced by the number of wolves in the pack and by the size of the prey species. Where moose predominate, a pack of nine wolves will kill a moose about every five days. Where prey are smaller than moose, kills occur more frequently. A pack of this size will make a kill, on average, every three days where the prey consist of mixed species such as deer and elk, or every two days where the prey are restricted to deer. |
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Carbyn photo |
Wolves do not kill haphazardly — they select those individuals that are easiest to kill. This selection usually means taking smaller prey over larger, and young-of-the-year or old individuals over those in the prime of life. Selection of fawns and calves during summer has been widely reported. Wolves target vulnerable individuals. Prey may be most vulnerable when debilitated by starvation, accident or disease, when old and infirm, or during extreme snow conditions.
The effect of wolf predation on prey populations has been the subject of intensive research and scientific debate. Generally, when prey are healthy, in good habitat and without other major limiting factors, wolf predation alone should not cause a decline. However, where populations of caribou, elk, moose or other prey have declined as a result of a combination of factors, such as severe winter weather, hunting and predation, wolves may kill enough animals to hold such herds at a low level for a long period of time. In this situation, wolf predation, often in combination with other predators, especially bears, becomes the major limiting factor.
The impact of wolf predation is not easily assessed; a lot of hard work is involved. The large size of wolf territories necessitates the use of aircraft, off-highway vehicles, and always lots of horse travel or hiking to capture and mark wolves, observe and count prey, or search for kills and other signs of the food habits of wolves. Researchers must be experienced in field work, animal capture and handling, radio-telemetric monitoring, and have extensive knowledge of the ecology of the area. The costs of these long-term (one to several years) projects are large; Alberta is fortunate that several projects have been completed. Summaries of wolf-prey relationships in six areas are detailed below.
The impact of one pack of 9 to 13 wolves on moose was determined in the Alberta Oil Sands Environmental Research Program (AOSERP) area in northeastern Alberta. The researchers estimated 262 yearling and older adult moose in the territory of the Muskeg River pack on May 15, 1977. The number of adult moose consumed over the next year was calculated at 33 to 45, which was equivalent to 13-17 percent of the adult moose population. Because the moose recruitment rate (rate of calf production) was 19 percent, it was concluded that wolf predation was the major limitation on the apparently stationary or slowly declining, low-density moose population. However, recreational hunting was almost as important a factor in limiting the moose population as was wolf predation.
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In the Swan Hills, the Foley Lake pack of seven wolves consumed moose at a slightly greater rate than the Muskeg River pack. But, in the Swan Hills, the moose density was up to nine times greater than in the AOSERP area. The impact of wolves was therefore less pronounced.
Although wolf predation on cattle was the primary focus of the Simonette River studies, kills of wild ungulates were monitored. Minimum daily consumption of one wolf pack during 51 days in winter was 5.5 kg (12 lbs.) of moose per wolf, identical to that of the Muskeg River pack in the northeast. The Simonette moose population was stable at 1300 moose/1000 km2 during the years of greatest wolf numbers; and when wolves were controlled to a low level in 1979-1981, the moose did not increase. Wolves selected elk over moose and further selected calves over adults. Yet, despite predation and harvest by hunters, the elk herd held its own. The investigators related the low impact of predation in the instance to the diversity of prey — which included deer, wild horses, livestock and beaver, as well as a productive moose population in excellent habitat. The wolf population was at an artificially lower density because of recurrent control.
Near Nordegg, predation by two radio-monitored packs was observed during 1983-1986. In the high country west of the Bighorn Range, the Blackstone/Brazeau pack killed elk, moose, mule, deer, bighorn sheep and wild horses. During late winters of two years, a helicopter was used daily to accurately determine kill frequency. The pack made a kill, on average, every 2.5 days. Total annual kill was estimated at 112 (1983-84, 9 wolves) and 126 (1984-85, 11 wolves) animals. Elk were killed most frequently. The elk herd produced calves at a low rate. Numbers declined to very low levels of 4-7 calves/100 cows during mid-summers of 1985 and 1986. Because the pack hunted the elk nursery herds during July and August, their kill of calves was probably substantial. It was concluded that wolf predation was the major source of mortality to this declining, unproductive herd.
In Wood Buffalo National Park, where the world's largest free-roaming bison herd had been in decline since about 1970, wolf-bison interactions were studied during 1978-1981. Fifty percent of wolf activity observations were in close association with bison — 143 wolf-bison interactions were documented. One pack made a kill every 7 days, and 40 of 42 kills were bison. Low calf production, losses to wolves, diseases in bison and habitat deterioration (drying of the delta) were all important to the continuing decline of this herd with wolf predation considered the single most important factor.
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Jasper National Park is renowned for its diversity of large mammals. The impact of wolves here has been periodically evaluated since 1942. Cowan's observations in the 1940s, when wolves were controlled and ungulates were high in numbers, revealed that mule deer occurred disproportionately more in wolf scats than among all ungulates. Carbyn's work during 1968-1971, showed wolves concentrated on elk calves in summer with associated declines in calf ratios. Mule deer comprised 43 percent of the annual wolf diet. Dekker and his coworkers have postulated that wolf predation was a major factor in the decline of elk herds in the park's back country in the 1970s. They noted that denning wolves selected sites near elk calving areas. Finally during 1989-1992, John Weaver of the University of Montana examined predation by the park's Devona wolf pack which preyed more than expected upon deer and used moose, elk and bighorn sheep less than expected.
The Evolution of Wolf Management
