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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

August 1996

How deer to Wisconsin?

The results of a 3,000-hour study examine the thrills, the consequences and the future of maintaining a large deer herd in Wisconsin.

Bill Vander Zouwen

As summer lingers and hunting seasons approach, people start looking at deer through different eyes.

Some still see a beautiful, graceful animal with big brown eyes and soft fur turning from auburn red to dull brown. Some start seeing lean cuts of brisket, tenderloin and rump roast on the hoof. Some people start thinking about family get-togethers or honing their hunting skills. Many have already won or lost the annual battle with co-workers over who will take the last week of November as vacation.

On the other side of the fence, homeowners are cussing deer as their plantings and expensive ornamentals are chewed to the nub. Others are badly shaken as their damaged cars are towed to the body shop. Those who tend orchards and Christmas tree plantations calculate how to adjust their prices as deer literally eat up their profits.

Nearly everyone in Wisconsin is affected by deer, even if they rarely see one. All the values and problems that deer bring must be weighed against each other. Let no one say these matters were not carefully considered. Nearly 40 DNR biologists spent more than 3,000 hours gathering information from research publications and field studies, consulting with national experts and meeting with an interested public. The result was a 305-page environmental assessment measuring how Wisconsin's white-tailed deer management affects nature, neighborhoods, outdoor recreation, and both social and business climates.

The Wisconsin deer herd is so vast and the habitat so variable that wildlife managers have divided the state into 125 units to more capably manage the unique needs and resources in each smaller area. Deer numbers are estimated in each unit using census techniques, population models, surveys of summer fawn production, and by aging the deer registered by hunters each fall.

Population goals for each unit are based on how many deer the habitat can sustain; winter severity; ecological, social and economic concerns; as well as tribal treaty agreements. Goals in the northern forest country are based on how many deer the habitat can support over winter; in the southern farmlands by how tolerant people are to the crop damage and vehicle accidents deer cause. Most parts of southern Wisconsin could sustain more than 100 deer per square mile of habitat, but that is much more than people are willing to tolerate.

How deer affect other plants and animals

Deer are natural members of Wisconsin's wildlife community. Like people, deer definitely affect their environment. Whitetails are large herbivores that eat large quantities of a wide variety of plants. Large populations of deer definitely affect the abundance of plants they feed upon. Further, other animals that depend on certain plants for habitat are affected by deer. That's only natural, but when do the number of deer have too great an effect on the environment? That's a judgement call. Here's a summary of the key research findings:

Some leafy plants are stressed when deer populations swell to more than 12-15 animals per square mile. The foliage gets nipped back, which cuts into the plants' energy reserves and reduces successful reproduction. Plants like the bluebead lily and trillium are prime targets for deer.

Trees and shrubs, particularly cedar, oak and Canada yew, are favored deer foods. When deer populations rise above 20-25 per square mile, these trees are heavily browsed and have a tough time surviving.

Deer don't normally eat invertebrates, but insects that rely on certain plants may be harmed if the deer graze on their host species.

It is likewise unlikely that deer directly harm reptiles and amphibians, but deer may harm their habitat. For instance, the western glass lizard relies on the same shrubs that deer eat for shade in summer. On the other hand, some browsing keeps shoots from getting brushy and opens up areas where reptiles can sun on colder days.

There is limited evidence that as deer numbers rise above 25 per square mile, habitat for small mammals is destroyed. The red-backed vole, for instance, needs a dense understory of low plants to survive.

Deer numbers greater than 15-30 per square mile can browse back the shrubs and leafy plants some birds favor for food and cover. Populations of the black-throated blue warbler in northern Wisconsin and the more rare hooded warbler in southern Wisconsin could be affected by deer-browsed habitat.

It is unlikely that moose populations would be restored in Wisconsin where we maintain a large deer herd. Deer carry a brainworm that causes a lethal meningitis-like illness in moose. Elk, on the other hand, are not threatened by the meningeal brainworm nor do elk compete with deer for the same foods.

Deer are a primary food source for timber wolves, and deer populations definitely affect the number of wolves that Wisconsin can support. Given the current deer population, Wisconsin could theoretically support more than 400 wolves. If we reduce northern Wisconsin deer herds to 10 animals per square mile, maximum wolf numbers would be reduced to about 140 animals.

Is the deer herd self-limiting? Yes, but we work to keep the herd below that density. As the herd approaches the habitat's carrying capacity, deer mortality increases, reproductive rates drop, the herd gets weaker and less healthy. Also, the shrubs and trees that deer eat take an awful beating when the deer herd gets too numerous.

How the deer herd affects the economy and social concerns

The deer herd size creates both opportunity and consequences for people.

As densities approach 20 deer per square mile of deer habitat, the herd can browse enough trees to substantially reduce the yield of high-value trees. Pine plantations and Christmas tree operations are particularly hard hit by large herds. Orchardists and farmers also feel the pinch from a large herd. Damage to corn, soybeans, alfalfa, hay, vegetables, strawberries and fruit orchards increases as the herd size grows.

On the fringes of urban development, deer eat ornamental plantings and damage native plants.

As traffic volumes increase and the deer herd grows, the number of car-deer collisions also increases. Every year, more than 40,000 deer collide with cars on highways and back roads. These accidents injure people, kill deer and cause an estimated $90 million in damage claims. Some auto body shops report 25-50 percent of their income is generated by car-deer collisions. The accident rates are high in most urban and rural areas where deer numbers exceed 25 per square mile.

Though deer carry some diseases that can be transmitted to other wildlife, domestic animals and humans, growing deer populations don't appear to increase the incidence of transmitted diseases at herd sizes we have managed.

On the other hand, a large deer herd is a real pleasure for those who enjoy the challenge of hunting whitetails, eating venison, making fine sausages, sharing the camaraderie of a deer hunt, feeding deer or just watching white-tailed deer throughout the seasons.

Fully two-thirds of the people who like to watch wild animals chose white-tailed deer as their favorite animals to see in the wild. More than two million Wisconsin residents are wildlife watchers and they spend about $500 million on their hobby.

Deer hunters annually buy $500 million worth of goods and services. These purchases generate $30 million in sales taxes and income taxes related to the hunt. More than 8,000 people make a living from jobs directly related to deer hunting. License fees deer hunters pay contribute $16 million each year to conservation programs carried out by the Department of Natural Resources. The hunting public also funds the majority of the Wildlife Damage Program that reimburses farmers for deer damage to crops.

Chippewa Indian Tribes have special treaty rights to a portion of the allowable antlerless deer harvest in the ceded territory of northern Wisconsin.

How deer herd size changes effective management

Hunters must take about the same number of deer as are born each year to control herd growth. Not all deer population goals are manageable or realistic. If the deer population goal is set too low, hunters are not as attracted to the area, and they are less willing to shoot antlerless deer. Consequently, these herds grow quickly. On the other hand, if the deer goals are set too high, the number of antlerless deer that must be harvested exceeds hunter demand for permits.

Experience shows that deer hunts are most successful when deer population goals are maintained around 50 percent of the area's carrying capacity. This wildlife principle is called the maximum sustained yield. Though most hunters would prefer to shoot a buck, many are happy to have the opportunity to take does. More than 400,000 hunters apply annually for antlerless deer permits. Yet, this demand is not high enough to control the southern Wisconsin deer herd at that 50 percent level; lower population goals are needed there.

Currently, deer herds in some units are well above goals – so high, in fact, that our traditional hunting seasons and permit systems can't keep the herd size under control. Consequently, the hunting and nonhunting public needs to work with professional managers to consider alternatives. Clearly, some deer herds need to be reduced to a more manageable level. Changes in the hunting season, like those adopted in 19 units for this fall, will sometimes be necessary.

One over-riding concern is how to manage the herd size on properties that have been closed to hunters. Keeping the herd size in check would help the land, the property owner and the hunter. Traditionally, Wisconsin has not needed incentives to convince nonhunting landowners to allow responsible hunting on their property. Perhaps those traditions are changing and we need to explore other options.

One segment of society recommends curtailing deer hunting and merely letting "nature take its course. That is possible, but not practical. Nature is no longer so natural; people have altered ecosystems too greatly. Animals that would prey on deer are absent or far less abundant than would be needed to control the herd size. Our land uses have changed the number of deer that can live in an area. Home development may increase or reduce the deer population. Agriculture provides more artificial food sources, increasing the potential herd size. Forest management practices during the last century have changed the mix of trees in our forests, supporting more deer than were found here before European settlement.

In fact, if we just let nature take its course now, deer numbers would be substantially higher. Who would willingly absorb the additional costs in crop loss, greater numbers of car-deer collisions and over-browsing of wild habitats? Who would stand by idly as the deer herd became less healthy, had fewer fawns or succumbed to disease and starvation?

The public is increasingly aware that a large deer herd has both positive and negative effects in Wisconsin. Hunters and wildlife managers are not the only people who want or deserve a voice in deciding how many deer should be maintained. A wider range of public interests are entitled to a place at the table as deer management decisions are made.

Wildlife managers are making a concerted effort to reach out to a wide range of interests. Seventeen regional Citizens Task Forces have reviewed the deer herd size, discussed how deer affect people and the environment, and recommended deer population goals in their parts of the state. At task force meetings hunters, foresters, farmers, wildlife specialists, environmentalists, motorists and others brought their concerns and desires to the fore. These groups have had the chance to better understand the problems each interest faces and the opportunities that deer herds bring. Their recommendations are being adopted by wildlife managers in most deer management units.

Deer management will continue to be a complex endeavor. Better information and more forums for public discussion are helping develop common understanding and consensus on directions deer management programs should take. Wildlife managers will continue to include a diverse mix of stakeholders throughout Wisconsin as goals, policies and practices for managing the deer herd are carried out.

Bill Vander Zouwen is chief of DNR's Wildlife and Landscape Ecology Section in the Bureau of Wildlife Management. The 305-page environmental assessment on which this article is based, "Deer Population Goals and Harvest Management" is available for $10 from the DNR Bureau of Wildlife Management, P.O. Box 7921, Madison, WI 53707.