The white-tailed deer of North Manitou Island

The white-tailed deer population on North Manitou Island, Michigan, was studied between June 1980 and May 1982. The National Park Service acquired the island in 1980, ending many years of deer hunting and winter feeding administered by the previous owners. A heavy dieoff in the winter of 1977-78 was the result of cessation of winter feeding by the private owners. Winter mortality was low in the following years as the severely reduced population began to increase. The population increased by an estimated 66 percent in 1980 and 59 percent in 1981 to a pre-winter population estimated at 2,080 deer. In a second major dieoff in the winter of 1981-82, an estimated 76 percent of the population died. Fawns were most susceptible to winter mortality, and males were more susceptible than females among adults. Favorable spring-through-fall foods, including grasses, forbs, fruits, and an unusual food, a fish (the alewife), many of which die in annual cycles in Lake Michigan, support high population productivity. However, woody browse has been largely eliminated by previous deer browsing, with the exception of American beech, an unpalatable species. The lack of quality woody browse for winter food and the lack of winter thermal cover make the population highly susceptible to winter mortality. The combination of favorable habitat from spring through fall and poor habitat in winter in a region with severe winter conditions can be expected to continue the historic pattern of rapid population increases followed by massive winter losses. This pattern can be broken. Hunting can control deer population numbers and allow regeneration of a more natural mix of woody species.