Wolf-moose interaction on Isle Royale: The end of natural regulation

Document Type


Publication Date



Long-term population fluctuations of wolves and moose in Isle Royale National Park, Michigan, are used to evaluate a central tenet of the 'natural regulation' concept commonly applied by the National Park Service (NPS) in the United States, namely, that wild cervid populations exhibit density dependence which, even in the absence of large predators, will stabilize population growth. This tenet, restated as a hypothesis, is rejected based on moose population response to a chronic wolf decline. In 1980-1996 with wolf numbers down, partly due to introduced disease, moose numbers increased to a historic high level. There was insufficient density dependence in moose reproduction and mortality to stabilize moose numbers. In 1996 moose suffered a crash; 80% died, primarily from starvation. These fluctuations, along with the possibility that the highly inbred wolf population may become extinct, will challenge NPS policy. The long-standing NPS management tradition of nonintervention may not be compatible with the current policy that stresses maintenance of natural ecological processes, such as a predator-prey system.

Publication Title

Ecological Applications