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Assessing Factors That May Predispose Minnesota
Farms To Wolf Depredation on Cattle

Introduction


Wolf (Canis lupus) depredations on livestock are a serious concern to Minnesota farmers, resource managers, agricultural officials, environmentalists, and state legislators. The wolf in Minnesota is currently on the federal endangered species list in the "threatened" category. However, because wolf numbers there have exceeded recovery levels (B. Berg and S. Benson, unpublished report, 1999), the federal government will soon propose removing the wolf in Minnesota from the endangered species list. Minnesota will then be responsible for wolf management, and continued control of wolves preying on livestock will be one of the greatest management needs (Mech 1998).

Although the total proportion of farms in wolf range that suffer verified wolf depredations is only about 1% per year (W. J. Paul, unpublished report, 1998), several factors must be considered to provide a more complete understanding of the importance of wolf depredations: 1) because it is difficult to verify wolf depredations, far more livestock may be lost to wolves than are verified (Roy and Dorrance 1976, Fritts 1982); 2) to farmers who do suffer damage, the loss is real and significant economically, even though partially offset by state compensation payments for verified losses; 3) over a period of years, livestock from hundreds of farms have been preyed upon; 4) number of farms sustaining such damage is increasing at an accelerating rate (Mech 1998); 5) wolf range is currently expanding into some of Minnesota's greatest densities of livestock (Minnesota Agriculture Statistics 1997); and 6) the wolf population has reached a level at which standard hunting and trapping techniques may be unable to prevent increases (Mech 1998).

Wolf
The wolf has reached federal recovery levels in Minnesota, Wisconsin, and Michigan.
Since 1978, when the wolf in Minnesota was downlisted from federally endangered to threatened, the United States Fish and Wildlife Service and then the United States Department of Agriculture's Wildlife Services (WS) have conducted lethal control of wolves around farms where depredations have been verified (Fritts 1982, Fritts et al. 1992), a program costing $300,000 in 1998. In addition, the Minnesota Department of Agriculture currently pays about $67,000/year in compensation for livestock confirmed lost to wolves. Conservative projections of these 2 costs exceed $400,000/year for the next few years (Mech 1998).

Concurrent with the increase in wolves and wolf range, the number of wolves killed for depredation control has increased dramatically from 6 in 1979 to 216 in 1997. Projections show that a conservative estimate of the number of wolves that may need to be killed for depredation control by 2005 might exceed 400/year (Mech 1998), a serious concern to wolf advocates and environmentalists (Anderson 1999).

Calf killed by wolf
This study attempted to find animal husbandry or habitat factors that distinguished farms suffering chronic depredations to wolves from those that did not. The calf in foreground was killed by a wolf.
There has long been a belief that wolves prey on livestock because of poor husbandry practices by farmers. This could be a misinterpretation of the claim that "many instances of wolf depredation on livestock in Minnesota seem to be related to animal husbandry practices" (Fritts 1982:7), a statement which implicates poor husbandry practices but does not place sole blame on them for wolf depredations. Acknowledging that "data collection on these issues was not extended beyond that taken for the earlier report," Fritts et al. (1992:14) indicated that "any further conclusions are subjective" and that "research is needed to . . . determine the causes of the onset of stock-killing behavior." Fritts (1982) and Fritts et al. (1992) identified 3 factors as potentially predisposing livestock to wolf depredations: 1) pasturing in wooded-brushy areas, 2) calving in wooded-brushy areas or in remote open range rather than in or near barns, and 3) improper disposal of carcasses, which can attract carnivores; this practice could affect the farm involved or even neighboring farms. Similarly, livestock depredations in western Canada seem to be related to the forest-agricultural edge (Gunson 1983, Bjorge and Gunson 1985), livestock production in forested areas (Gunson 1983), and improper carcass disposal (Tompa 1983). Gunson (1983) also stated that livestock depredations at these edges are influenced by the number of livestock present, animal husbandry practices, and potentially relative abundance of natural prey.

We sought to assess the role of suspected major factors that may predispose cattle to wolf depredations and to attempt to elucidate any unknown factors. We did not intend to examine such basic husbandry practices as maintaining herds in good health and nutrition and taking reasonable care of them.


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