Academic journal article The American Midland Naturalist

Effects of White-Tailed Deer (Odocoileus Virginianus) on Plants, Plant Populations and Communities: A Review

Academic journal article The American Midland Naturalist

Effects of White-Tailed Deer (Odocoileus Virginianus) on Plants, Plant Populations and Communities: A Review

Article excerpt

ABSTRACT.-Large effects of white-tailed deer (Odocoileus virginianus) upon individual plants, plant populations and communities have been documented in a number of studies. However, well-supported experimental measures of the magnitude and geographical extent of these effects are still surprisingly scarce. Deer-caused changes in stem morphology and reductions in plant growth rates are well-documented in some parts of the North America. Furthermore, deer have been shown to affect the composition of several plant communities in the north-central and northeastern United States. There are some documented cases of deer-caused reductions in plant survival; most of these are tree seedlings and saplings. However, many studies have detected no effects on plant survival or fecundity, or have found that negative effects occur only in a fraction of years, seasons, sites or deer densities. Little is known about population-level or ecosystem-level impacts. Many regions and plant communities with large deer populations have not been studied. Whereas deer density is clearly important in determining spatial and temporal variation in the presence and magnitude of deer effects, other factors that may modify the effects of deer density are poorly understood.

INTRODUCTION

In many parts of the eastern United States and south-eastern Canada white-tailed deer (Odocoileus virginianus (Boddaert)) are currently so abundant that many observers have suggested or assumed that deer are having a major impact upon the vegetation of this region (Leopold, 1950; Hough, 1965; Behrend et al., 1970; Whitney, 1984; Alverson et al., 1988; Michael, 1992; Strole and Anderson, 1992; Van Auken, 1993; Boerner and Brinkman, 1996; Phillips and Man, 1996; Van Deelen et al., 1996; Catling and Larson, 1997; Buckley et al., 1998). Whereas substantial evidence exists that in some community types deer negatively affect the growth rate of tree seedlings and saplings, prevent adult recruitment into tree populations and alter species composition, experimental evidence for widespread (relative to the range of white-tailed deer in North America or to the geographic area over which deer populations recently have increased) substantial effects are less than frequently appears to be assumed. Here we summarize current knowledge about the nature, magnitude and spatial and temporal patterns of the effects of white-tailed deer upon individual plants, plant populations, plant communities and ecosystem processes and identify major gaps in our current knowledge. We also review some methodological challenges in obtaining more conclusive evidence of deer effects.

Management of deer populations is a contentious issue that has stirred emotional conflict between individuals who want to avoid the extirpation by overbrowsing of rare aesthetically pleasing or economically valuable plants and plant communities (Diamond, 1992; Diefenbach et al., 1997) and individuals who consider hunting deer to be cruel (McShea and Rappole, 1997), hunters who enjoy the abundance of deer (Diefenbach et al., 1997) and land managers who distrust human intervention in "natural" processes within wildlife refuges and preserves (Diamond, 1992). However, the effects of deer herbivory on vegetation are also of interest to ecologists examining the effects of herbivores on individual plants, plant populations and communities. By reviewing this literature we hope to provide information to aid land managers in evaluating the need to hunt deer to preserve rare or economically valuable plant species and to preserve or restore rare plant communities. In addition, we hope to enhance ecologists' understanding of the effects of herbivores on plants and the mechanisms that underlie these effects.

This review will be confined to effects of white-tailed deer, although similarly high densities of related species present similar problems elsewhere (Gill, 1988; Clutton-Brock and Albon, 1992; McInnes et al., 1992; Singer and Renkin, 1995). …

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