The wolf and moose populations on the Island follow a pattern of dynamic fluctuations, where high numbers of moose are followed by higher wolf numbers. Wolves influence moose numbers predominately through direct killing of calves and are the only consistent source of moose mortality on the Island. The moose-wolf population patterns held until a dramatic crash occurred in the wolf population in the early 1980's, in which wolf numbers dropped from 50 to 14. As the moose population grew throughout the 1980s and 1990s, the wolf population failed to increase correspondingly. Concern over the decline of the wolf population in the late 1980s prompted the convening of a group of scientists representing NPS management, wolf ecologists, disease and genetics experts and conservation biology specialists.
Uncertainty remains over the causes of the wolf decline.
Results from this research suggest that canine parvovirus played an important role in the population crash. High mortality in 1981-88 would have accelerated genetic decay in the wolf population. It is estimated that there has been a 50 percent loss of genetic variability in Isle Royale Wolves. Condensed from the Michigan DNR's Michigan Gray Wolf Recovery Plan available online at this Michigan Department of Natural Resources Wildlife Division site. The gray wolf population on Isle Royale has risen to 29, two years after a sharp drop prompted fears that the animals' days in the Lake Superior national park might be numbered.