By Jake Rossen
By Jesse Marx
By Michelle LeBow
By Alleen Brown
By Maggie LaMaack
By CP Staff
By Jesse Marx
In Wisconsin, Waller says, many game managers were highly dismissive of his claims that deer constituted an ecological threat. "When I started raising these concerns, I was told that I was alarmist and that the impacts I was seeing were local and temporary," he says. With the accrual of evidence, Waller adds, attitudes there have begun to shift.
At the Minnesota DNR, there is still a reluctance to concede that whitetails are causing much damage to the forests--especially among the agency's employees who work in game management.
Tom Soule, a wildlife coordinator for the DNR in northwestern Minnesota, cautions against applying Waller's research in Wisconsin to Minnesota. "That doesn't mean deer aren't impacting our landscapes, but there's just not much sound data to tell a story," Soule says. "We just have lots of anecdotes."
One area that has received little formal study is the effect that the deer herd is having on other animal species. It is widely acknowledged that the high deer numbers have been a major reason for the successful wolf recovery in Minnesota. And it has also long been known that deer carry a parasitic brain worm that is harmless in whitetails but fatal to other large ungulates, such as woodland caribou, elk, and moose. In Minnesota, the impacts of brain worm on woodland caribou and elk are irrelevant. Caribou have been gone from Minnesota for more than a century, and there just a few dozen elk left in the state.
But there are still about 10,000 moose in Minnesota, mostly in the Arrowhead region in the northeast. For reasons that are not clear, the bearded beasts have gone into decline in the past decade. While the brain worm is not thought to be a major factor, the continued expansion of whitetail into moose country is a hazard to the moose recovery in those areas.
Over the long term, there are suggestions that our growing deer herd will have a deleterious effect on other animals as well, mostly small mammals and various bird species. If the number of white pines in the state continues to decline because of overgrazing by deer, for instance, there will probably be a drop in the bird species like pine warblers that rely on a white pine habitat.
In greater danger may be those birds that dwell in the denuded forest understory. Joann Hanowski, a research fellow with the Natural Resources Research Institute in Duluth, has noted a dramatic decline in ground-nesting birds such as white-throated sparrows and ovenbirds. While there has been little study of the issue, damage to the understory plants by deer is considered one likely explanation.
It is also possible that deer are threatening ground-nesting bird populations in a much blunter manner. Despite Bambi's reputation as a gentle vegan, whitetails are omnivores; their broad palate is a reason they are such an adaptable and successful animal. In the scientific literature, there are accounts of deer feeding on everything from dead fish to shed antlers to nesting birds.
Steve Windels, a terrestrial ecologist at Voyageurs National Park, witnessed this last behavior a few years back while banding songbirds along Hawk Ridge in Duluth. As he approached the mist net--a fine mesh used by researchers to capture birds--Windels noticed a healthy-looking doe and fawn ambling by.
"They were just walking around, foraging," Windels recalls, "and then they came up to the net and munched about half a dozen birds that were caught in it. I was pretty shocked, but they were just being opportunistic."
The whitetail population explosion is also likely having an effect on the health of another large and common animal that lives in Minnesota. Surprisingly, it is an area of inquiry that has received little attention to date. What is known is this: More and more Minnesotans are becoming infected with Lyme disease after being bitten by deer ticks. In 2002, according to the Minnesota Department of Health, there were a record 867 cases of Lyme disease in the state. While the ticks don't pick up Lyme disease from the deer--the white-footed mouse first infects the parasites--deer do play a vital role in the life cycle of the tick. In the second year of life, the adult ticks live and mate on the deer.
Is it a coincidence that the rising incidence of Lyme disease and other tick-borne illnesses such as ehrlichiosis has been accompanied by a spike in the deer population? In Minnesota, the matter has not been explicitly studied. But in the northeast states, where 90 percent of Lyme disease cases occur, researchers have linked the prevalence of Lyme to the expanding population of white-tailed deer. Studies have shown that 95 percent of adult female deer ticks feed on whitetails.
Does that mean that a reduction in the deer population in Minnesota might reduce the incidence of Lyme disease? The verdict is out--in part, because no one is yet asking the question.
There is nothing "natural" about the deer herd anymore. In Minnesota, where deer hunting is something of a cross between religion and big business, this central fact has received precious little attention. For decades, the Department of Natural Resources has viewed deer hunters as one of its most important constituencies. Befitting that view, the agency has managed the hunting season with an eye toward maximizing the population.