PARASITE-MEDIATED COMPETITION IN DEER AND MOOSE: HOW STRONG IS THE EFFECT OF MENINGEAL WORM ON MOOSE?

摘要: It is widely acknowledged (1) that meningeal helminths (Parelaphostrongylus tenuis) carried by white-tailed deer (Odocoileus virginianus) but fatal to moose (Alces alces) and other cervids, have caused widespread population declines where invaded the ranges of (2) worms can alter outcome interspecific competition between cervid hosts, (3) populations persist on enzootic range in habitat refuges not frequented deer. Further, some attempts reintroduce cervids now occupied failed. However, been observed sympatric with deer, there evidence at least one introduced growing, events (such as change) are confounded presumed effects worms. Thus, it still clear whether mortality individual attributed necessarily has dynamics ascribed it. Using conventional host-macroparasite models, we describe moose, intermediate gastropod parasite determine conditions under which worm might be implicated populations. The analysis resulted three general scenarios depending magnitude parameters affect transmission rates different phases life cycle, parasite-induced rate difference competitive ability moose. First, when larval consumption hosts definitive were all small, was large, excluded Second, could coexist either a stable or unstable equilibrium. Stable coexistence occurred rates, differences large; then outnumbered Unstable equilibrium opposite conditions; more abundant than Finally, competitively exclude To these cases most plausible, substituted available estimates for from published literature, solved equations numerically, conducted sensitivity analysis. Overall, model solutions sensitive mag- nitude effect intrinsic increase host-all little empirical information. We conclude that, information, cannot ruled out factor contributing deciines our analyses suggest many cases, should become extinct. This implies reintroductions (and perhaps cervids) need fail necessarily. Moose may able albeit lower densities, even absence disease.