The white-tailed deer : a keystone herbivore

During the last 3 centuries, sweeping manipulations of habitat for agriculture, silviculture, and, to a lesser degree, game management have improved and expanded habitat for white-tailed deer (Odocoileus virginianus) across much of the landscape in the eastern United States. For most of this century, wildlife managers sought to protect and enhance populations of deer. With the specter of extirpation still haunting their memory, wildlife managers worked hard in the early 20th century to devise and enforce bag limits, short hunting seasons, and buckonly hunts in order to protect the recovering herds. As they professionalized, wildlife managers were quick to follow Leopold's (1933) suggestion that the way to manage game is to manage habitat. For whitetailed deer, this meant favoring edge and early successional habitats by creating gaps and grassy openings in regions dominated by mature forest. Clearcuts, in particular, continue to be promoted for their immediate production of slash for browse and their ready succession to shade-intolerant species such as aspen (Populus spp.) that provide good summer browse, at least for a few years (e.g., Masters et al. 1993, Johnson et al. 1995). Nearly a decade ago, we warned wildlife professionals and conservation biologists about the ecological consequences of overabundant deer populations (Alverson et al. 1988). Since then, deer populations and their ecological and economic impacts appear to have increased and worsened. As we approach the next millennium, it behooves wildlife managers to contemplate what consequences will result from their actions in their own professional lifetimes. We hear more each year about the high costs of crop and tree-seedling damage, deer-vehicle collisions, and nuisance deer in suburban locales (Conover et al. 1995). Beyond these substantial economic costs, however, we face new and often vexing issues regarding the ecological costs of overabundant deer. In some cases, it appears that these consequences will extend over decades and perhaps even centuries. This makes it even more important now than it was a decade ago that wildlife managers assume responsibility and take action to minimize the ecological effects of chronically overabundant deer populations. The wildlife management profession has begun to respond to the economic and ecological impacts of overabundant deer. In 1995, Wisconsin's Bureau of Wildlife elected to scrutinize the impacts of its own deer management policies via a comprehensive Environmental Assessment (VanderZouwen and Warnke 1995). This was the first attempt, that we are aware of, to seriously consider the broad range of ecological and environmental impacts pertaining to a state's deer management policy. Partly in response to this assessment, the Wildlife Bureau also began to institute new hunting regulations in some areas to ensure that more, especially more female, deer were killed (e.g., their 1996 Earn a Buck program). This, however, has proved to be a major challenge, both because it is difficult to adjust hunter effort as more areas become off-limits to hunting and because hunters favor a tradition and management they see as contributing to, rather than diminishing, their prospects for personal hunting success. Many hunters remain skeptical about the seriousness of deer impacts, or at least the need to reduce deer densities in their own areas (Diefenbach et al. 1997). Thus, in addition to facing the irony of having done their job too well,