The Role of Predation in Wildlife Population Dynamics

The role predation plays in the dynamics of prey populations is controversial. Our understandings of predator-prey relationships is complicated by a multitude of factors in the environment and a general lack of knowledge of most ecological systems. Various other factors, besides predation, may regulate or limit prey populations, and various factors influence the degree to which predation affects prey populations. Furthermore, some factors may create time lags, or even cause generational effects, that go unnoticed. Herein, we review the role of predation in wildlife population dynamics, some of the factors influencing predator-prey interactions, and attempt to indicate where the professional debate currently is focused and where it may need to go to enhance our understanding of predator-prey interactions. Predation has been defined as individuals of one species eating living individuals of another species (Taylor 1984). The role of predators in the population dynamics of prey species has been investigated for decades, yet determining whether or not predators limit or regulate a prey population remains controversial within the scientific profession (e.g., Erlinge et al. 1984, Kidd and Lewis 1987, Newsome et al. 1989, Sinclair 1989, Sinclair et al. 1990, Messier 1991, 1994, Skogland 1991, Boutin 1992, Pech et al. 1992). Much of the debate results from the multitude of competing variables, including predation, that influence demographics of prey species and the difficulty of conducting large-scale, longterm studies with some degree of control or replication. In a review of studies involving predation on ungulates, Connolly (1978) reported that 45 studies suggested predation was a limiting factor, while 27 studies indicated predation was not a limiting factor on ungulate density. Assessments of the importance that wolf (Canis lupus) predation plays in regulating or limiting moose (Alces alces) populations varies among biologists. Interactions among moose, forage, and climate have been postulated to determine moose density (Peterson et al. 1984, Mech et al. 1987, Thompson and Peterson 1988). Bergerud et al. (1983), Bergerud and Snider (1988), and Van Ballenberghe and Ballard (1994) considered predation a major limiting factor of moose because moose density was generally below forage carrying capacity. Messier and Crête (1985) and Messier (1991) argued that moose and predator interactions were complex and that the effect of predation varied from densitydependent to inversely density-dependent over the range of moose densities resulting in population cycles, multiple stable states, and predator pits. Skogland (1991)