Ecological Studies of Wolves on Isle Royale - Annual Report 1993-1994

Peterson, Rolf

In 1993-1994 wolf and moose populations at Isle Royale both increased. Wolf numbers reached 17 in January 1994, their highest level since 1987. Two of the three packs reproduced, each raising 4 pups. Eleven of fifteen wolves surviving in March 1994 were young - three years old or less. This younger generation contains both males and females, which will help secure the short-term future of the wolf population. Improved reproduction in the wolf population calls into question the hypothesis that poor reproduction in this small population was caused by inbreeding. Wolf food supply (old moose) began increasing in the early 1990's, and wolves may now finally be responding to improved food supply, in spite of genetic losses. The outcome of the next few years should help resolve this important question. The 1993 moose calf crop was larger than average, and the moose population continues to slowly grow. Mortality during the 1994 study included some losses to accidents and malnutrition, but wolves killed 70% of the moose recovered in winter. Winter ticks were not abundant in 1994, and the moose population will probably continue to grow until it is stopped by increased wolf predation, ticks, or winterkill. The previous moose increase (in the early 1970's) was evidently held in check by wolf predation.