Minnesotans For Sustainability^©

[ Home ] [ Up ] [ Feedback Please ] [ Table of Contents ] [ Search MFS ] [ MFS News ]

Sustainable Society:  A society that balances the environment, other life forms, and human interactions over an indefinite time period.

Wolf Depredation on Livestock in Minnesota

Steven H. Fritts¹

Abstract
Depredation by wolves (Canis lupus) on cattle, sheep, and other livestock in Minnesota currently is a minor problem except to a few individual farmers. Indices to the seriousness of the problem are available only from recent years, so historical trends cannot be detected. From 1976 through 1980 the number of farms in the wolf range suffering verified losses to wolves ranged from 9 to 19 ( = 13) per year out of about 12,230. From 1977 through 1980, the highest cattle losses claimed by farmers were 0.45 per 1,000 cattle available in 1979; the highest sheep losses claimed were 1.18 per 1,000 available in 1980. Many claims of losses (especially of calves) are based on missing animals, and few wolves are involved in the verified losses. Most losses occur in summer when livestock are released to graze in open and wooded pasture. Herd management practices, such as calving in forested or brushy pastures and disposal of carcasses in or near pastures, are responsible for many instances of wolf depredation. Failure to distinguish wolves from coyotes (Canis latrans) has contributed to an exaggerated view of the importance of wolves as livestock predators. Recently the number of wolves killed in depredation control has declined, whereas the number of livestock killed has remained fairly stable. Results of the U.S. Fish and Wildlife Service's depredation- control program in 1979 and 1980 suggest that highly restricted trapping, coupled with other management methods, has potential for reducing both livestock losses and the number of wolves that need to be killed.

Introduction

The range of the timber wolf (Canis lupus) in the lower 48 States is limited primarily to about 77,700 km² in northern Minnesota (Fig. 1), although this animal also inhabits Isle Royale (Peterson 1977), the Upper Peninsula of Michigan, and northern Wisconsin in low densities (Hendrickson et al. 1975; Thiel 1978; Mech and Nowak 1981). About 1,000 to 1,200 wolves are estimated to inhabit northern Minnesota (Bailey 1978). Although largely unsettled, the Minnesota wolf range includes about 12,230 farms, based on data from Minnesota Agricultural Statistics 1978 (Fig. 2). Most farms are located near the southern and western edge of the range. The ability of wolves to kill cattle, sheep, and other livestock is well documented (Young and Goldman 1944; Lopez 1978). For years, wolves have been accused of seriously menacing livestock production on many northern Minnesota farms; however, no studies have attempted to document the extent of the problem there, and no information about the problem has been published. The problem of depredations on domestic animals, together with the wolf-deer issue, has generated considerable controversy in Minnesota and produced negative publicity for the wolf and the agencies managing it. Local politicians historically have exploited the wolf-livestock issue to rally support from the local populace, and this practice continues today (The Daily Journal, International Falls, Minn., 14 December 1979).

Fig.1. Minnesota wolf range (north of dashed line) and distribution of farms (dots) where the U.S. Fish and Wildlife Service verified that wolves have killed livestock, 1975-80. B.I.S.F. indicates Beltrami Island State Forest; S.N.F. indicates Superior National Forest.

At least 90% of the farms within Minnesota's wolf range currently have some livestock; cattle, sheep, or both, are present on at least 80% of the farms (Joseph W. Rust, personal communication). About 234,000 cattle and 91,000 sheep were present during summer of 1979 (based on data from Minnesota Agricultural Statistics 1979). Cattle are present on farms throughout the wolf range, whereas most sheep production is in the northwestern part of the range. Within the past 10 years the number of sheep on farms in the wolf range has decreased by 54%; however, the number of cattle has increased by 10% (Minnesota Crop and Livestock Reporting Service 1969, 1979). During winter, cattle and sheep are confined or their movements are restricted to areas near farm buildings, but in late April or May they are released to graze in open and wooded pasture until about October (Fig. 3). During that period they are especially vulnerable to depredation by wolves, and this possibility is of great concern to many farmers.

Other types of livestock on northern Minnesota farms include swine, horses, goats, turkeys, chickens, ducks, and geese; these are usually less numerous and less vulnerable to depredation by wolves because of husbandry practices. Turkeys, however, are raised on open range in summer, primarily in the northwestern counties, and are vulnerable to wolves. Because most attention has been focused on depredations on cattle and sheep, this paper will deal primarily with those two types of livestock.

Historically, various management programs have been proposed or implemented to help alleviate wolf damage to livestock in Minnesota. Each of these has been based on the assumption that wolves are highly destructive to domestic animals, especially to cattle and sheep. Even the Eastern Timber Wolf Recovery Team assumed that the wolf was an important predator of livestock (Bailey 1978). One of the reasons given for the reclassification of the eastern timber wolf in Minnesota from "endangered" to "threatened" status in 1978 was that continued total protection was expected to result in colonization of rural areas and consequently increased depredations on livestock.

In general many persons interested in wolf management believe that wolves are highly detrimental to livestock production in northern Minnesota. The objectives of this paper are (1) to examine that assumption by using the best information available, (2) to describe the historical and current status of wolf depredation in Minnesota, and (3) to examine the approach and effectiveness of past and present programs designed to ameliorate the problem. Special attention will be given to the U.S. Fish and Wildlife Service's [FWS] depredation control program in 1979 and 1980.

History of Wolf Depredation Control Programs

From 1849 to 1965 a bounty program was in effect on wolves in Minnesota. Depredation on livestock was one of the reasons cited to justify this program. During its 116-year tenure, the bounty was renewed biennially by the State Legislature and administered by the Minnesota Department of Conservation (now Minnesota Department of Natural Resources [DNR]). During the 1950's and early 1960's, an average of 188 wolves per year were bountied for $35 each (Johnson et al. unpublished data). This program ended in 1965 when, despite considerable pressure and criticism, Governor Rolvaag vetoed the appropriation. Unfortunately, no data are available on the effect of this program on livestock depredations.

The Minnesota Department of Conservation also conducted wolf control until 1956. Department personnel used aerial hunting, snaring, and trapping to kill about 140-150 wolves annually from 1949 to 1954 (Anonymous 1980). Aerial hunting was terminated in 1954, and from 1954 to 1956, the annual take dropped to an estimated 70-90 wolves. From 1965 to 1969 there was no State wolf control program, although the public was allowed to take wolves. Until September 1974, anyone could legally kill wolves except in the Superior National Forest.

Fig. 4. Indices to recent wolf depredations on livestock in Minnesota, based on reports received by the U.S. Fish and Wildlife Service. Minnesota Department of Agriculture data are not included. Total number of complaints received is all complaints received involving wolves and livestock, regardless of whether wolves killed a livestock individual. Number complaints verified is number instances in which FWS investigation of a complaint produced evidence that wolves had killed or injured livestock. Each year after 1975 more than one complaint was verified at some farms. In 1975 the FWS had only a minor program (two trappers and no publicity), but enlarged its staff and publicity in 1976.

In 1969, the State Legislature funded a new "Directed Predator Control Program." It was implemented primarily because of coyote depredations on sheep in the northwestern counties rather than because of widespread depredations by wolves (Stenlund 1974). This program, still in effect, is administered by the DNR's Division of Enforcement. Registered local trappers are designated to remove coyotes (Canis latrans), foxes (Vulpes vulpes), bobcats (Felis rufus), lynxes (Felis lynx), and wolves (before September 1974) that are reported to be damaging domestic animals or wildlife. After verifying a complaint, enforcement personnel designate (1) the area around a farm to be open for predator control, (2) the species to be taken, (3) the period over which control can be conducted, (4) the control methods to be used, and (5) the controllers who can participate. Controllers were paid $50 for each wolf taken, $35 for each coyote, lynx, or bobcat, and $5 for each fox. No limit was set on the number of wolves that could be taken.

Some fraud has been discovered in the program. For example, one wolf killed in the Superior National Forest was transported 130 km to a designated control area where the controller claimed it had been killed (L. D. Mech, personal communication). From 1 July 1969 through August 1974, 293 wolves were trapped and killed (Minnesota DNR files). Records are insufficient to determine the number of claims of damage resulting from wolves or the number of claims verified.

In August 1974, the Endangered Species Act of 1973 took effect in Minnesota. This Act provided complete legal protection to wolves in the State. The maximum penalty for violation of provisions of the Act was set at imprisonment for not more than 1 year, a fine of not more than $20,000, or both (Endangered Species Act of 1973:35-37). Taking of wolves on the State's Directed Predator Control Program terminated on 5 September 1974. Thereafter, farmers were dependent on the Federal Government for protection from wolf depredations.

Wolf control was initiated by the FWS in early 1975. FWS trappers responded to complaints of wolf-livestock problems by livetrapping wolves on or near the problem farms. Because of the Endangered Species Act, the FWS was prohibited from killing wolves captured at the farms from 1975 through early 1978. Therefore, Federal personnel tried translocating the wolves into remote areas of northern Minnesota. In 1975, 17 wolves were livetrapped in response to complaints; 51 were captured in 1976 (including 1 recapture of a translocated wolf); and 59 in 1977, including 9 recaptures.

Fig. 5. [depredation fig6] Total number of wolves captured and number removed from the population by livestock-depredation control programs in Minnesota, 1970-79. All wolves captured on Minnesota directed control program were killed. Data for 1970-74 represent State fiscal years. Four wolves captured in late summer 1974 are included in fiscal year 1974. Data for 1975-79 represent calendar years.

Altogether, 108 wolves were translocated (105 into the Superior National Forest and 3 into the Beltrami Island State Forest). Nine of these were translocated twice, and one was translocated three times. Nineteen of the wolves were radio-collared; their movements were subsequently monitored by aerial telemetry. The remaining 89 were only ear- tagged for identification. Radio-tracking revealed that most of the wolves left their release sites within a few days and eventually drifted back into or through areas containing livestock (Fritts et al., unpublished data).

Wolves were captured twice at only one farm. In that instance several wolves returned, and further livestock losses were reported there. This farm was the closest (51 km) to the release sites in the Superior National Forest. These data show that relocation of livestock-depredating wolves was not an adequate solution to the depredation problem. However, at the time the only legal alternative to translocating wolves was holding them in captivity.

This FWS program received considerable criticism from wolf preservationists. In some instances livetrapping was authorized after livestock had been chased by wolves. In other instances, trapping was conducted following sightings of wolves at farms where losses had previously occurred. At times, trapping was conducted over extended periods and for distances of up to 8 km from some farms. Many farmers were also critical of the program, claiming that they often had to wait too long before receiving assistance.

The classification of the wolf in Minnesota was changed from "endangered" to "threatened" in April 1978 (FWS 1978), following the recommendations of the Eastern Timber Wolf Recovery Team (Bailey 1978). This new rulemaking (FWS 1978) allowed livestock-depredating wolves to be killed by authorized State or Federal personnel after the wolves had committed "significant depredations on lawfully present domestic animals . . . (4). Furthermore, such designated employees or agents of the Service or the Minnesota Department of Natural Resources may take a gray wolf without a permit in Minnesota if such action is necessary to remove from Zone 2, 3, 4, or 5, as delineated in paragraph (d) (3) (1) of this section, a gray wolf committing significant depredations on lawfully present domestic animals, but only if the taking is done in a humane manner."

"Significant depredation" was later defined by the FWS as "the killing or serious maiming of one or more domestic animals by wolves where the imminent threat of additional domestic animals being killed or severely maimed by wolves is apparent" (memo by L. A. Greenwalt, Director, FWS, 12 April 1978). This change in classification was intended to provide greater protection for farmers and reduce local opposition to wolves while providing ample protection for wolves as required by Federal law.

In 1978 wolf captures totaled 40, 4 of which were recaptures of animals translocated in previous years. Twenty-six wolves were killed that year under the modified Federal program. Five wolves were translocated in 1978 before the new rulemaking, but later two of these were recaptured and killed. The remaining wolves were given to zoos or died in handling.

During summer of 1978 several environmental groups claimed that the FWS was not following its own regulations. They objected especially to the trapping procedure at a farm 50 km southeast of International Falls where wolves were being taken as far as 8 km from the farm-wolves that, in the opinion of the environmentalists, probably had not killed cattle at the farm. In fact, 78 (47%) of the 167 wolf captures on the FWS program from 1975 through 1978 were within 8 km of this one cattle ranch because of depredations there.

The groups filed suit against the FWS. Subsequently a Federal judge clarified what already had been implied in the Federal regulations by ordering that control trapping and killing of wolves must be done only after a significant depredation occurs and that the trapping must, as nearly as possible, be directed toward the capture of the wolf or wolves responsible (Federal judge P. McNulty court order, 14 July 1978). To reduce the chances of catching non-depredating wolves, the Federal judge restricted trapping to within 0.4 km of the affected farms. Furthermore, killing of pups was prohibited because the judge did not consider them depredating animals. To comply as much as possible with the court order, the FWS required that three specific conditions be met before trapping could be initiated: (1) presence of a wounded animal or some remains of a livestock carcass, (2) evidence that wolves were responsible for the damage, and (3) reason to believe that additional losses would occur if the wolves were not removed. The Service's trapping program was adjusted in compliance.

Meanwhile, a State program provided up to $100,000 in compensation to farmers for losses of livestock destroyed by wolves in fiscal years 1978 and 1979 (Minnesota Statutes 1978, Section 3.737). Supporters of this legislation claimed that livestock depredations were proliferating and that farmers were sustaining considerable financial losses. The new law provided compensation of up to $400 per animal for livestock killed or injured by wolves. The responsibility for verifying claims of wolf depredation and determining the market value of the livestock was given to the local DNR conservation officer and the University of Minnesota Agricultural Extension Service's county extension agent, respectively. This program was still in effect in 1980.

Despite the long history of the wolf-livestock problem in Minnesota and the controversy it continually generates, until recently no agency had measured the amount of damage actually caused by wolves. Therefore, it was difficult to evaluate and compare the effectiveness of any of the past programs or to detect long-term trends in the seriousness of the problem. Records of the number of complaints and verified depredations were available only since 1975, and records of the number of wolves taken in livestock depredation control programs were available only since 1969. Records of the number of livestock claimed killed have been kept by the Minnesota Department of Agriculture (MDA) since 1977 and by the FWS since 1979.

Many residents of northern Minnesota believed that depredations on livestock increased after wolves were legally protected in September 1974. In northwestern Minnesota, there likely was some increase from 1974 to 1976 (Fritts and Mech 1981); however, from 1975 through 1980 the total number of complaints, the number of verified complaints of livestock losses to wolves, and the number of farms in Minnesota with verified losses remained fairly stable (Fig. 4). The number of wolves captured by State and Federal depredation control programs varied considerably during the past decade, but generally declined, as did the number killed (Fig. 5). Although it was not possible to assess the precise effect of the decreased number of wolves killed during recent years, one can conclude that no great increase in livestock losses resulted. Certainly no widespread proliferation of losses has occurred between 1975 and 1980 as indicated by the number of farms where losses were verified by the FWS (Fig. 4), although during each year of this period substantial losses were claimed by a few individual farmers.

These findings suggest that proponents of the State's livestock compensation program overestimated the seriousness of the wolf depredation problem. During the first 9 months of the program no claims were filed, due in part to the lack of public awareness of the new program. Some compensation payments were made in 1978 for losses claimed to have occurred in 1977 (Table 1); nevertheless, even in 1978, the claims totaled less than half of the original appropriation. A single sheep rancher received 66% of the total compensation paid for 1977 losses, and a single cattle rancher received 42% of the amount paid in 1978 and 51 % of that paid in 1979 (MDA files). These figures indicate that the State legislators' perceptions of the seriousness of wolf-livestock depredations were exaggerated.

Table 1. Compensation paid by Minnesota Department of Agriculture for livestock destroyed by wolves.

Problems in Verification of Wolf Depredation

Verifying depredation on cattle, sheep, and other livestock is often difficult (Roy and Dorrance 1976). Many of the northern Minnesota farms reporting wolf depredations have pastures that include extensive areas of brush or dense forest. When cattle, especially young calves, die in this type of habitat, either from predation or other causes, there is little chance for farmers to find them. This is especially true where livestock are checked infrequently during summer. In 1979, 76% of the cattle reported to the FWS as having been killed by wolves were cattle that could not be accounted for. About 73% of the calves for which compensation was paid by the MDA in 1979 were calves that could not be accounted for; no remains were found, and no wolf involvement was verified. Possibly some of the calves claimed missing were never born. Fewer than 20% of the beef cattle herds in northern Minnesota are pregnancy tested, and testing is especially uncommon among smaller beef cattle operations such as most of those within the wolf range (Pilgram 1978). Cows released into pasture before calving in the spring may be assumed to be pregnant when they are not. If the herd is pastured in forested or brushy areas where they cannot be observed closely, wolf involvement may be inferred by the farmer if no calf is found with a cow in autumn. In one recent complaint, a farmer thought that 60 calves were lost to wolves during one summer, but only 4 were found and considered by FWS personnel to have been killed by wolves. Pregnancy testing of the herd in the next autumn showed that at least 40 (27%) of 150 cows thought to be pregnant were not. Because most of these cows were in the herd the previous year, the very existence of at least some of the 60 calves can be questioned. Considering that most calves claimed lost to wolves are "missing," lack of proof of pregnancy is an important problem in documenting loss claims.

Wolves occasionally may consume or carry away the entire carcass of a young calf, and therefore leave no evidence of predation; however, a variety of other mortality factors may also be involved. In northwestern Albert, where wolves are present, cattle losses over a 4-year period ranged from 1.3% of herds in one area to 3.3% of herds in another. Many of the losses were not found, so cause of death could not be determined. Predators caused only 19 (about 16%) of 121 cattle deaths whose cause could be determined, wolves being involved in 15 instances and bears in 4; pneumonia and poisonous plants contributed 56% of the known mortality (R. R. Bjorge, personal communication).

In some instances, carcasses are found too long after death and are too decomposed to allow determination of cause of death; decomposition of cattle and sheep carcasses is especially rapid in mid-summer. At other times the animal is found soon after death, and obviously has been fed upon, but there is no indication of which carnivore was involved. Even if there are tracks and droppings of wolves nearby, the animal could have died of pneumonia, for example, and then been scavenged by wolves.

In addition to wolves, domestic dogs, bears, and bobcats also can kill young calves and especially sheep. Coyotes are notorious sheep predators and they also kill calves in Minnesota, as FWS personnel documented in 1979 and 1980. Coyotes probably are more important predators of domestic animals in northern Minnesota than are wolves. From July 1969 through August 1974, the ratio of coyotes to wolves captured on the State of Minnesota's Directed Predator Control Program was 17:1. Coyotes are usually far more abundant than wolves in most areas of northern Minnesota where sheep, cattle, and turkeys are produced (Berg and Chesness 1978). When investigating complaints of wolf depredations, FWS personnel commonly find evidence of coyotes also being at the farm. From 1975 through 1980, at least 10 % of the complaints of wolf depredations received by the FWS were determined to have resulted from coyotes. It is the judgment of FWS personnel that compensation has been mistakenly paid for losses to coyotes on at least one farm, and possibly on others, since 1977.

The similarity between coyotes and wolves probably has led to a distorted view of the importance of wolves as livestock predators. Many northern Minnesota residents use the term "wolf" in referring to both wolves and coyotes. Coyotes are often called "brush wolves" but the "brush" may be dropped, and both species referred to merely as "wolves." When wolves were given legal protection in 1974, many Minnesotans assumed coyotes were protected.

There also is a prejudice among certain farmers toward wolves as the cause of their livestock losses. Wolves are usually blamed if their tracks have been seen in or near the pasture, if howling has been heard, or if neighbors have claimed wolf depredations in the recent past. Another possible reason for implicating wolves is that compensation can be obtained for livestock killed by them, whereas none is available for losses by other predators (including coyotes) or from other causes (St. Paul Dispatch, St. Paul, Minn., 18 June 1980). In Italy, where farmers are compensated for sheep killed by wolves, wolves are estimated to account for only 20-50% of the alleged wolf damage reported by farmers (Zimen and Boitani 1979). The existence of a compensation program in Minnesota probably results in biased damage claims there too.

Human involvement in the disappearance of livestock is rarely suspected by farmers living in wolf range. However, some poaching and rustling of livestock occurs in northern Minnesota (Grand Rapids Herald Review, 20 December 1979).

The Problem in Perspective

What portion of the cattle and sheep available to wolves in northern Minnesota actually are killed by wolves? Arriving at an exact figure is impossible because of the problems mentioned above. However, the number claimed lost, based on reports to the MDA's compensation program and to the FWS, should give a reasonable indication. Claims of losses were made independently to these two agencies. Although records of loss claims by the agencies were similar, occasionally claims made to the MDA were not made to the FWS, and vice versa.

Based on data from these sources, the most cattle lost from 1977 through 1980 was reported to the FWS in 1979 when 7 cows and 98 calves were claimed. The 105 cattle represented about 0.45 per 1,000 available. Many of the calves could not be accounted for; merely circumstantial indications, or no evidence, of wolf involvement was available. The highest sheep losses claimed since 1977 was in 1980, when the State's compensation program paid for 36 ewes and 72 lambs (Table 1). These sheep represented about 1.18 per 1,000 available.

During 1979, the FWS conducted a preliminary survey of 55 livestock producers in north-central Minnesota. Ten of 4,970 head (0.20 per 1,000) of livestock (mainly beef cattle) at these farms were thought by the farmers to have been killed by wolves that year. The percentage of livestock producers affected by wolf predation is also small. The highest number of farms reporting complaints to the FWS was in 1976 when 35 farms (3 per 1,000) complained of harassment or depredation of livestock. Moreover, losses to wolves were verified at only 19 (1 in every 640) of these farms. Even if only 90 of the 12,230 farms within wolf range have some form of livestock, the vast majority (over 99% in 1976) of livestock producers in northern Minnesota are not affected by wolves (Fig. 1).

Most wolves do not kill livestock even when that food is available. In northwestern Minnesota, wolf packs lived very near farms without killing livestock (Fritts and Mech 1981). Territories of at least five radio-instrumented packs in the Beltrami Island State Forest bordered marginal farmland where livestock (primarily cattle) were produced, yet only one instance of depredation by these packs was verified in a 5-year period. Remains of livestock were found in 29 (3%) of 960 wolf scats collected within that study area, primarily from territories of packs that bordered some farmland. Although most of these scats probably represented scavenged cattle, six contained remains of young calves that likely had been killed by wolves (Fritts and Mech 1981). Similarly, livestock remains were found in only 1 % of 1,608 scats collected in Riding Mountain National Park in Manitoba. The park is surrounded by farmland where cattle are produced; territories of several packs bordered farmland there (L. N. Carbyn, personal communication).

Many instances of wolf depredation on livestock in Minnesota seem to be related to animal husbandry practices. For example, cattle depredations are fostered by pasturing in extensive woodlots or brushy areas and allowing calving in such areas or even in remote open pastures. These practices also make it more difficult to keep track of the herd and determine the causes of mortality. In Alberta, total cattle losses over a 4-year period were higher in a predominately forested area (3.3% of herds) than where 50% or more of the trees had been cleared and herd management was more intensive (1. 3 % of herds; R. R. Bjorge, personal communication). In Minnesota, radio-collared wolves living near farms are frequently located in wooded habitat adjacent to open pasture, but very rarely in open pasture (Fritts and Mech 1981). Therefore, cattle in a wooded habitat probably have a greater chance of being encountered by wolves.

Another practice that probably encourages and perpetuates depredations is improper disposal of livestock that died from other causes. When investigating complaints of depredations, it is not uncommon for FWS personnel to find remains of dumped carcasses in or near the pasture (Fig. 6), even though State law (Livestock Sanitation Law 35.82) requires that carcasses be buried or burned: "Except as provided in subdivision lb, every person owning or having in charge any domestic animal that has died or been killed otherwise than by being slaughtered for human or animal consumption, shall as soon as reasonably possible bury the carcass thereof at least three feet deep in the ground, or cause the same to be consumed by fire . . . ;"

Fig. 6. Cattle carcasses at a disposal site on a northern Minnesota cattle ranch. This type of illegal disposal is thought to encourage wolf depredations.

Nonetheless, many farmers dispose of dead animals improperly because proper procedures are less convenient. In a preliminary survey that FWS personnel made of 111 farmers in north-central Minnesota in 1979, 63% indicated that they either leave dead animals where they die, or transport them to the edge of the pasture, into the woods, or to a regular dumpsite on the farm. Remains of butchered animals also are left at these sites (Fritts and Mech 1981). Wolves are known to scavenge from livestock carcasses in Minnesota (Fritts and Mech 1981), as they also do in Alberta (R. R. Bjorge, personal communication). FWS personnel observed that wolves frequented carcass dumps at farms in Minnesota. This free disposal service is even welcomed by many farmers. It is possible that many wolves that ultimately kill livestock receive their first taste at a carcass dump. The experience might be their first step in learning to kill live prey of the same odor, appearance, and taste. Moreover, the presence of livestock carrion on Minnesota farms may encourage wolves and coyotes to frequent pastures which in turn increases the probability of contact between predators and domestic animals. Either higher coyote density or increased activity, or both, were found close to a cattle carcass dumping area in Arizona (Danner and Smith 1980). In Alberta, overwinter coyote numbers near some farms were greatly reduced by removal of livestock carrion (Todd and Keith 1976). Availability of carrion probably has a similar effect on wolves.

Farmers sometimes permit baiting for bears in their pasture where livestock depredations have occurred. Placement of any meat or other substance that would attract wolves and encourage their return to a pasture should be avoided.

The 1979-80 Approach to Wolf Depredation Control

In May 1979 the FWS transferred the responsibility for livestock depredation control to its Patuxent Wildlife Research Center, and the control program was subsequently modified. The objective of the new program was to reduce livestock losses but take the minimum number of wolves necessary.

Complaints of wolf-livestock problems were investigated by FWS biological technicians within 24 h to increase the chances of confirming or disproving wolf involvement. After finding livestock remains to verify that a loss had occurred (or observing wounded livestock), and obtaining hard evidence of wolf involvement, an intensive effort was made to trap the offending wolves within 10 days. Trapping was then terminated if no further losses occurred, whether or not the number of wolves thought involved in the depredations were caught. This policy was based on the assumption that if no additional livestock were lost during the 10-day period, it was questionable whether the wolves would return and kill again. If further losses occurred during the period, trapping was extended an additional 10 days after each loss. In 1980 this policy was changed to allow trapping for up to 21 days in the few instances where depredations recur at a farm within the same year.

In compliance with court orders, trapping was restricted to within 0.4 km of the farm on which the losses occurred. Limiting the duration and area of trapping greatly increased chances that any wolf captured would be an offender. Adult wolves captured in traps were euthanized and necropsied. Pups were released, as required by court order. However, beginning in 1980, young of the year captured after September were euthanized. By October these young are approaching adult size and beginning to travel with their packs. They may be capable of participating in the killing of some livestock, especially sheep, by this time.

In some instances up to 16 highway flasher lights were installed around the pasture when traps were removed, or sometimes when traps were set. In addition 1-m-long strips of surveyor's flagging were draped from fences and trees in pastures to blow freely in the breeze and perhaps frighten off some wolves. Similar flagging is used in hunting wolves in eastern Europe and the USSR to funnel the wolves toward shooters as a group of drivers pushes the wolves (Carbyn 1977).

Another approach used to alleviate livestock damage involved an attempt to establish taste-aversion conditioning by baiting (Gustavson et al. 1976). Baits consisting of ground beef mixed with a solution of lithium chloride and wrapped in cowhide were distributed on and near four cattle ranches with a history of livestock losses. It was hoped that wolves would consume the baits, become ill, and develop an aversion to the taste of beef.

Results of the 1979-80 Approach

During 1979 the FWS received 29 complaints of wolf-livestock problems. FWS personnel confirmed that in 15 of the instances (12 farms) wolves had killed livestock. (More than one complaint was verified at a few farms.) The number of individual livestock claimed lost to wolves in 1979 were 7 cows, 98 calves (remains of only 14 were found), 1 sheep, and 3 chickens. Losses judged by FWS personnel to be wolf kills (verified losses) were 5 cows, 12 calves, 1 sheep, and 1 chicken.

During 1980, 40 complaints of wolf-livestock problems were received. In 26 instances (17 farms) wolves had killed or wounded livestock. The number claimed lost were 10 cows, 45 calves, 73 sheep, 1 foal, and 56 turkeys. Losses verified by FWS personnel as wolf kills were 4 cows, 12 calves, 56 sheep, 1 foal, and 56 turkeys. The major difference between total losses reported and losses verified by FWS personnel were cattle and sheep that could not be accounted for (no remains were found).

The most feasible and objective method of evaluating the effectiveness of the 1979-80 approach is to compare indices to depredations in these years with indices from previous years. Probably the best indicators of the overall seriousness of the depredation problem are the number of farms suffering verified losses within a year, the number and types of animals lost, and the number of complaints verified. Both FWS and MDA records include data that can be used in this evaluation; these records date back to 1975 and 1977.

The number of complaints verified by the FWS and the number of farms where depredations were verified in 1979-80 were within the range of those for other recent years (Fig. 4). Unfortunately, FWS records of the number of livestock claimed lost from 1975 through 1978 are too incomplete to compare with 1979 and 1980 figures; however, the number of livestock on which the MDA paid compensation in 1979 and 1980 was similar to 1977 and 1980 figures (Table 1). Therefore, the extent of the depredation problem seems to have changed little in recent years.

The number of complaints verified and the number of farms where losses were verified by the FWS were slightly higher in 1980 than in 1979 (Fig. 4); a similar increase appeared in MDA figures (Table 1). The increase in verified complaints was due in part to repeated complaints at two farms. A reduction in calf losses from 1979 to 1980 was offset by an increase in sheep losses. Sheep were killed at four farms, two of which were sites of losses before 1980. Although the number of farms sustaining livestock losses has increased slightly since 1977 (Fig. 4), it is not yet possible to determine whether the trend is real.

Although MDA and FWS records of depredations were comparable in both 1979 and 1980, two of the MDA's indices to depredations were higher in both years (Table 1; Fig. 4). The number of claims paid by the MDA was higher than the number of complaints verified by the FWS, and the number of farmers to whom claims were paid was higher than the number of farms where the FWS verified losses. The total number of complaints received by the FWS, however, exceeded the number of claims received by the MDA because complaints sometimes only involved sightings of wolves, whereas compensation claims had to involve an actual loss or claimed loss. The MDA paid compensation for more individual livestock than the FWS considered killed by wolves in 1979 and 1980 because of more lax verification criteria for the State compensation program and because some farmers who filed compensation claims to the MDA failed to complain to the FWS.

Another important consideration in evaluating the overall effectiveness of the 1979-80 approach is the number of wolves killed. Because the wolf is classified as "threatened" in Minnesota, the FWS should minimize the number of wolves it kills for depredation control while still alleviating depredations effectively. Except for 1975, when the FWS suddenly had to assume the control program and was unprepared, the number of wolves captured during control activities in 1979 and 1980 was the lowest in a decade (Fig. 5). In 1979, 15 wolves were captured, but 9 were released as pups; only 6 adults were killed. Of 26 wolves captured in 1980, 5 were released and 21 were killed. The increase from 1979 to 1980 resulted from responding to more complaints (14 vs. 27) and likely also from increased effectiveness of technicians in trapping at farms. The reduction in wolves captured in 1979 and 1980 vs. previous years resulted from more tightly regulated trapping.

The effectiveness of specific depredation-control methods in controlling losses is difficult to evaluate (Griffiths et al. 1978). Insufficient funds were available to attempt actual controlled studies of the several actions taken. In fact, controlled studies may not be feasible because of the sporadic nature of depredations and the small number of farms involved and livestock killed. Results of the taste aversion baiting are still not conclusive.

Although some farmers believed that the blinking highway lights kept wolves away at night, our findings are ambiguous. During a few occasions at a farm in winter 1979-80, tracks of wolves were found in the snow approaching the lights, but there was no indication that wolves had walked past or between lights spaced about 60 m apart. Losses occurred at 4 of 11 farms where lights were up during summer of 1979 and 1980. Wolves killed sheep within 45 m of a light at one farm and 30 m of a light at another in 1980; however, it was impossible to determine whether the depredations occurred at night or during the day when the lights were off. In one of the instances mentioned above, wolves definitely returned and fed from the carcasses at night when the light was functioning, and traveled within 3 m of the light while entering the pasture. Several instances of coyotes traveling between lights were noted, although the time of day was not known. In general the lights seemed more effective in smaller and open pastures than in large wooded ones where it was virtually impossible to surround livestock effectively with them. The same appeared to be true of the flagging.

During 1979 and 1980 our trapping efforts were successful in 22 (54%) of 41 attempts (instances of verified losses in which the FWS responded by setting traps). We found it difficult to correlate the number of wolves removed at a farm with a reduction in the loss rate, as no or few wolves were trapped at some farms, yet these same farms suffered no additional verified losses. In 1979 there were six farms where losses were sustained but no wolves trapped; none of these farms reported verified losses in 1980. Three of six farms where wolves were trapped in 1979 were the scene of losses again in 1980. Also, among 17 farms where wolves were trapped in 1979 and 1980 combined, eight additional losses were verified following trapping. It seems that depredations at some farms may stop even though few or no wolves are removed; at other farms depredations continue despite wolves being captured regularly.

The results stated above, together with observations by FWS personnel from 1975 through 1978, reflect an important distinction among farms where depredations occur. Such farms fall into two broad categories: those with a history of losses, occurring at least once every 3 years (Type I), and those where losses are infrequent, occurring once or twice over a period of several years (Type II). Losses at Type I farms usually result from a depredating pack living nearby and having regular contact with cattle or sheep. At present, about 10 Minnesota farms fall into this category; many other farms may have packs nearby but have very few or no losses. Trapping efforts at Type I farms usually result in wolves being captured.

Losses at Type II farms seem to be caused most often by single, non-territorial wolves that spend little time in one area. Nine of 29 (31%) farms where the FWS trapped in 1979 and 1980 fit this classification. Trapping rarely results in the capture of wolves at these farms. In the Type II situation the depredations usually stop by themselves, probably because the offending wolf soon leaves the area. Trapping serves no apparent useful purpose in such situations, so a short trapping period is appropriate there, especially if there is no evidence that the depredating wolf has remained near the farm.

Even at Type I farms that are visited regularly by packs, depredations are sporadic both between and within years. Only two farms seem to have been the site of regular annual losses since 1975. This indicates that extremely few wolves regularly depend on cattle and sheep for food. Trapping at Type I farms eliminates some of the offending wolves, but usually not all pack members can be trapped. Breeding adults are older and more experienced and thus are the most difficult to capture. Even if the offending pack members are eliminated, other members sharing the depredation tradition may eventually reinitiate the depredations.

When several wolves spend considerable time in a pasture and regularly encounter cattle and sheep, the potential for depredations is greatly increased. The opportunity for this is influenced by husbandry practiced at the farm. Thus, trapping would not be expected to indefinitely alleviate losses at Type I farms. Nevertheless, FWS records show that removal of three or more members of a depredating pack was followed by a reduction of losses at 10 Type I farms during the past 6 years. On the other hand, depredations stopped or decreased at approximately 13 Type I farms even though 0-2 wolves ( = 1.3) were trapped. Trapping seems to have a positive effect at most Type I farms, but the extent of trapping that is necessary to reduce losses is not obvious.

The effect of releasing trapped pups cannot yet be determined; however, among three farms where pups were released in 1979, two suffered losses again in 1980. A pup released at the third was recaptured at a neighboring farm in 1980 following cattle losses.

Conceivably, evaluation of the 1979-80 program should be based on future losses as well as those occurring during these years alone. If too many depredating wolves were left uncaptured, depredations might increase in some areas; however, at present there is no evidence that a successful livestock depredation control program must include taking large numbers of wolves. To do so without capturing the offending ones probably does little to alleviate the problem.

Conclusions

Wolf depredations on livestock in northern Minnesota are not as serious as generally believed. A small percentage of farms in the wolf range are affected annually, and a minute fraction of the livestock in the area are killed by wolves. In fact, the low incidence of depredation is remarkable in view of the proximity of wolves and livestock in an area where husbandry practices predispose many herds and flocks to depredation by wolves. Many claims of livestock losses to wolves are based on the disappearance of animals. A few farmers suffer chronic wolf depredations, and monetary loss at certain individual farms may be substantial in a given year; however, even at chronic problem farms, losses are sporadic, both between and within years. Real wolf problems are localized in nature, and few wolves are involved.

Trapping and removal of wolves seems to reduce losses at most farms, but the extent of trapping that is necessary to reduce losses is not obvious. At some farms, depredations stop even though few or no wolves are removed. At other farms, depredations recur across the years despite regular removal of wolves. The difference seems to be related to (1) whether a pack or transient single wolf is involved, (2) farm management practices, (3) differences in behavior of specific wolf packs, and (4) wolf density near the farm. Because few wolves are involved in verified losses, and many wolves live near farms without killing livestock, trapping should be directed toward the capture of specific offending wolves rather than local populations. Results of the FWS's depredation control program in 1979 and 1980 suggest that depredations can be controlled without taking large numbers of wolves. Whether this will remain true is, of course, unknown. In 1979 and 1980 trapping was supplemented by alternate means of control including taste aversion baiting and placement of flagging and highway flasher lights at some farms. Additional study will be required to determine the effectiveness of these methods in reducing losses.

Many questions about the wolf-livestock problem need more complete answers. More research needs to be done to determine the exact nature of the problem and its possible solutions. It would be worthwhile, for example, to closely examine management practices at farms with verified losses and compare them with those at similar farms located nearby, but not experiencing losses. Also, cattle mortality studies at certain farms where calves disappear would be especially elucidating. Research should be directed toward developing more effective means of minimizing livestock losses while reducing the number of wolves that have to be killed.

Acknowledgments

The assistance of L. D. Mech and W. J. Paul in preparation of this manuscript is gratefully acknowledged. R. R. Bjorge, Alberta Fish and Wildlife Division, and L. N. Carbyn, Canadian Wildlife Service, offered suggestions for its improvement. W. R. Jones, W. J. Paul, and R. S. Wetzel provided data from the FWS wolf depredation control program from 1975 through 1978. C. R. Gustavson directed taste-aversion studies conducted in 1979 and 1980. D. Boyd, R. K. Field, T. J. Meier, and J. D. Smith provided technical assistance. The Minnesota Department of Natural Resources furnished information from State-administered wolf control programs, and the Minnesota Department of Agriculture provided data from its compensation program for livestock destroyed by wolves.

References

Anonymous. 1980. Minnesota gray wolf management plan. Minnesota Department of Natural Resources, St. Paul, Minnesota. 20 pp.
Bailey, R., editor. 1978. Recovery plan for the eastern timber wolf. U.S. Government Printing Office, Washington, D.C. 79 pp.
Berg, W. E., and R. A. Chesness. 1978. Ecology of coyotes in northern Minnesota. Pages 229-247 in M. Bekoff, ed. Coyotes: biology, behavior, and management. Academic Press, New York, N.Y. 384 pp.
Carbyn, L. N. 1977. Report on Canadian Wildlife Service involvement in IUCN-WWF wolf project (1240) in Poland. Submitted to IUCN Survival Service Commission Wolf Group. 44 pp.
Danner, D. A., and N. S. Smith. 1980. Coyote home range, movement, and relative abundance near a cattle feedyard. J. Wildl. Manage. 44:484-487.
Fritts, S. H., and L. D. Mech. 1981. Dynamics, movements, and feeding ecology of a newly-protected wolf population in northwestern Minnesota. Wildl. Monogr. 80:1-79.
Griffiths, R. E., Jr., G. E. Connolly, R. J. Burns, and R. T. Sterner. 1978. Coyotes, sheep and lithium chloride. Proc. Vertebr. Pest Conf. 8:190-196.
Gustavson, C. R., D. J. Kelly, M. Seeney, and J. Garcia. 1976. Prey lithium aversions I: Coyotes and wolves. Behav. Biol. 17:61-72.
Hendrickson, J., W. L. Robinson, and L. D. Mech. 1975. Status of the wolf in Michigan-1973. Am. Midl. Nat. 94:226-232.
Lopez, B. H. 1978. Of wolves and men. Charles Scribner's Sons, New York, N.Y. 309 pp.
Mech, L. D., and R. M. Nowak. 1981. Return of the gray wolf to Wisconsin. Am. Midl. Nat. 105:408-409.
Minnesota Crop and Livestock Reporting Service. 1969. Minnesota Agricultural Statistics. U.S. Department of Agriculture Statistical Reporting Service and Minnesota Department of Agriculture, St. Paul. 95 pp.
Minnesota Crop and Livestock Reporting Service. 1978. Minnesota Agricultural Statistics. U.S. Department of Agricultural Statistical Reporting Service and Minnesota Department of Agriculture, St. Paul. 79 pp.
Minnesota Crop and Livestock Reporting Service. 1979. Minnesota Agricultural Statistics. U.S. Department of Agriculture Statistical Reporting Service and Minnesota Department of Agriculture, St. Paul. 86 pp.
Peterson, R. 0. 1977. Wolf ecology and prey relationships on Isle Royale. U.S. Natl. Park Serv. Sci. Monogr. Ser. 11:1-210.
Pilgram, G. 1978. The Minnesota beef cow-calf industry and analysis of management practices. Minn. Agric. Ext. Serv., Ext. Bull. 438-1978. 27 pp.
Roy, L. D., and M. J. Dorrance. 1976. Methods of investigating predation of domestic livestock. Alberta Agriculture, Edmonton. 53 pp.
Stenlund, M. H. 1974. Trials of the timber wolf. The Minnesota Volunteer, March-April, 50-61.
Thiel, R. P. 1978. The status of the timber wolf in Wisconsin-1975. Wis. Acad. Sci. Arts Lett. 66:186-194.
Todd, A. W., and L. B. Keith. 1976. Responses of coyotes to winter reductions in agricultural carrion. Alberta Fish Wildl. Div., Wildl. Tech. Bull. 5. 32 pp.
U.S. Fish and Wildlife Service. 1978. Title 50. Wildlife And Fisheries. 43(47):9607-9615.
Young, S. P., and E. A. Goldman. 1944. The wolves of North America. Dover Publications, Inc., New York, N.Y. 632 pp.
Zimen, E., and L. Boitani. 1979. Status of the wolf in Europe and the possibilities of conservation and reintroduction. Pages 43-83 in E. Klinghammer, ed. The behavior and ecology of wolves. Garland STPM Press, New York, N.Y. 588 pp.
_______
1. U.S. Fish and Wildlife Service
Patuxent Wildlife Research Center
Laurel, Maryland 20708

[ Home ] [ Up ]

Please send mail to webmaster@mnforsustain.org with questions or comments about this web site. Minnesotans For Sustainability (MFS) is not affiliated with any government body, private, or corporate entity. Copyright © 2002 Minnesotans For Sustainability