Deer population thrives despite wolves, hunters

By Michael E. Nelson

In 1974, I joined L. David Mech’s U.S. Interior Department wolf study in Ely, which he had started in 1968. I was a graduate student conducting deer research to complement wolf research, which began my 36-year career capturing and radio tracking wolves and deer in the Superior National Forest.

That first winter, I attended a deer hunters’ meeting in International Falls. Disappointed hunters voiced that the “infestation of wolves killing deer” was a problem that needed a solution. At the time, 700 wolves in Northeastern Minnesota and 40 on Isle Royale in Lake Superior were the last remaining wolves in North America south of Canada. Today, 48 years later, the wolf population in northern Minnesota has recovered to a stable 3,000 wolves, a success of the Federal Endangered Species Act of 1973.

Not surprisingly, history repeated itself this fall just after deer-hunting season when the voices of some disappointed hunters called for a reduction in the wolf population because the wolves were supposedly decimating northern deer. This sentiment among hunters stems directly from a random pattern of mild, moderate, and severe winters when the deepest snow of the severe winters impedes the ability of deer to forage, depleting their energy and ultimately leading to starvation, and an inability to escape predation by their ancient and primary predator, the wolf. The above-average mortality of deer in those years resulted in fewer deer available to be hunted in the following hunting season.

The 4 million-year evolutionary relationship between deer and wolves, the results from my Ely deer research (1974-2010), and Glenn D. DelGiudice’s deer research for the Minnesota Department of Natural Resources at Grand Rapids (1989-2006) provides insight to the antiquity of the wolf-deer/predator-prey system.

First and foremost, Glenn and I independently recorded an 80% annual survival rate of 200 does at Ely and 300 at Grand Rapids. Most of the 20% mortality was caused by wolf predation during December through April. The high survival rate occurred in a stable resident-wolf population at Ely and in a recently recovered one at Grand Rapids. The average annual deer harvest in Minnesota’s wolf range was 96,000 deer from 1989 through 2006. The yearly high-doe survival in the presence of a stable wolf population coupled with a high harvest demonstrated both biological success by deer and wolves and conservation success by modern humans.

Equally instructive was the buck harvest in relation to snow depth on the ground. During wolf recovery in Minnesota, the number of bucks killed by hunters in 5,000 square miles adjacent to Ely demonstrated what wildlife managers had long understood about the negative impact of deep-snow winters on northern deer populations. The buck harvest increased by 15% following 15 winters averaging 12-inch weekly snow depths, but the buck harvest decreased by 30% following four winters that averaged 24-inch weekly snow depths. These results can only be explained by fewer 8-month-old buck fawns surviving winters with deeper snow. Wolf predation on Ely fawns doubled to 30% during weekly snow depths exceeding 18 inches. After those winters, six months later in November, fewer 1½-year-old bucks were available to hunters.

The long-term evidence during wolf recovery demonstrated that it is not Minnesota’s wolf population that caused declines in deer harvest, but rather the depth of snow from December through April. This “provided conclusive evidence that wolves and deer can fulfill their natural relationship as predator and prey in the region,” according to DelGiudice.

Michael E. Nelson of Prescott, Arizona, and formerly of Ely and Duluth is a retired wildlife research biologist for the U.S. Geological Survey. He wrote this for the Duluth News Tribune.

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