Population dynamics of moose in the western Upper Peninsula of Michigan, 1999--2001

Moose (Alces alces americana) are native to Michigan but were possibly extirpated from the entire state by the end of the 19th century. With the goal of reestablishing a self sustaining population of moose in the Upper Peninsula of Michigan, the Michigan Department of Natural Resources (MDNR) translocated 61 moose (59 of which were released) from Ontario, Canada to western Marquette county in the winters of 1985 (n = 31) and 1987 (n = 30). Based on evaluations of potential habitat and optimistic population growth projections the objective was to have a self-sustaining population of 1000 moose by the year 2000. However, population size estimates from aerial surveys conducted in the winters of 1996 and 1997 were well below 1000. To evaluate the possible reasons for the slower than expected population growth, 84 moose were captured and radio-collared in the winters of 1999--2001. Survival of all age classes has been excellent; annual survival of adults was >85% and first-year calf survival >70%. Seventy-four percent of adult cows were pregnant which is lower than the 84% average for moose in North America. In addition, radio-tagged moose, primarily yearlings, have dispersed out of the study area at an annual rate of about 6%. Preliminary indications are that low reproductive output is the likely cause of the slower than predicted population growth.