Deer-predator relationships: A review of recent North American studies with emphasis on mule and black-tailed deer

Publication Type:Journal Article
Year of Publication:2001
Authors:Ballard, WB, Lutz, D, Keegan, TW, Carpenter, LH, J. J.C, DVos
Journal:Wildlife Society Bulletin
Volume:29
Date Published:2001
Keywords:Canis lupus
Abstract:

In recent years mule (Odocoileus hemionus) and black-tailed (O. h. columbianus) deer appear to have declined in many areas of the western United States and Canada, causing concern for population welfare and continued uses of the deer resource. Causes of the decline have not been identified, but predation by coyotes (Canis latrans), mountain lions (Puma concolor), and wolves (Canis lupus) has been proposed as one of many factors. We reviewed results of published studies conducted since the mid-1970s concerning predator-deer relationships to determine whether predation could be a factor in the apparent deer population declines and whether there was evidence that predator control could be a viable management tool to restore deer populations. We reviewed 17 published studies concerning mule deer. We found only 4 published studies of the effects of predation on black-tailed deer. A larger database existed for white-tailed deer (O. virginianus), with 19 studies examining effects of predation on white-tailed deer. Study results were confounded by numerous factors. A deer population's relationship to habitat carrying capacity was crucial to the impacts of predation. Deer populations at or near carrying capacity did not respond to predator removal experiments. When deer populations appeared limited by predation and such populations were well below forage carrying capacity, deer mortality was reduced significantly when predator populations were reduced. Only one study, however, demonstrated that deer population increases resulted in greater harvests, although considerable data indicated that wolf control resulted in greater harvests of moose (Alces alces) and caribou (Rangifer tarandus). The most convincing evidence for deer population increases occurred when small enclosures (2-39 km2) were used. Our review suggests that predation by coyotes, mountain lions, or wolves may be a significant mortality factor in some areas under certain conditions. Relation to habitat carrying capacity, weather, human use patterns, number and type of predator species, and habitat alterations all affect predator-prey relationships. Only through intensive radiotelemetry and manipulative studies can predation be identified as a major limiting factor. When it is identified, deer managers face crucial decisions. Reductions in predator densities have occurred only on relatively small study areas (2-180 km2) where predators were identified as a major limiting factor and deer populations were well below forage carrying capacity (an important criterion). Thus a problem of scale, methods used to kill predators, benefit:cost ratios, results to hunters, and public acceptance are primary considerations. Methods of predator control available to deer managers have been severely restricted and current methods may not be feasible over large areas when and if predation becomes a problem. Public acceptance of predator reduction programs is essential for predator-prey management, but may not be achievable given current public attitudes toward predators. We identified several recommendations and research needs based on our review of the literature given current social and political limitations.

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