LIMITATION AND REGULATION OF MOOSE POPULATIONS - THE ROLE OF PREDATION

An improved understanding of factors limiting and regulating ungulate populations is vital for sound management, especially with regard to c ontroversial factors like predation. We examine the claim that evidenc e is weak for predation acting as a major factor limiting or regulatin g moose (Alces alces) populations in North America. Biologists have be en inconsistent in defining limitation and regulation, have used these terms interchangeably, and have incorrectly assumed that major limiti ng factors regulate moose density. Empirical evidence indicates that m any moose populations preyed on by both bears (Ursus arctos and U. ame ricana) and wolves (Canis lupus) persist at densities much lower than K/2 when human influence is minimal. Under these conditions, reduction of predator numbers often results in increased moose density. Reducti on of moose from high densities with predators held constant results i n inversely density-dependent (anti-regulatory) predation and low moos e densities for prolonged periods. In ecosystems lacking bears, or in those subject to substantial human influence, predation may not be a m ajor limiting factor, may vary greatly in its impact, and may be overs hadowed by interactions among moose, forage, weather, and hunting that primarily determine moose density. We conclude that in naturally regu lated ecosystems, predation on moose by bears and wolves is often limi ting and may be regulating, and we identify the conditions necessary f or this to occur.