North America's Most Dangerous Mammal

How best to deal with the menace of Bambi


What is North America's most dangerous (non-human) mammal? Grizzly bears? Certainly Lewis and Clark on their way to the Pacific Ocean in 1804 thought so. In the early 1800s, some 50,000 grizzlies roamed the western United States, but their population has now dropped to around 1,000 in the lower 48 states. Bears, grizzly and black, killed 128 people in North America in the 20th century. What about mountain lions? Reports that mountain lions lurk in the hills and pick off women trail bikers certainly chill the blood. There have been 14 deaths in North America as a result of mountain lion attacks in the 20th century.

No, there is another creature roaming America's woods that is far more dangerous than these big predators. The most dangerous mammal in North America is…Bambi. The U.S. Department of Transportation estimates that white-tailed deer kill around 130 Americans each year simply by causing car accidents. In 1994, these predator deer had a banner year, causing 211 human deaths in car wrecks.

There are about 1.5 million deer/vehicle collisions annually, resulting in 29,000 human injuries and more than $1 billion in insurance claims in addition to the death toll. Deer also carry the ticks that transmit Lyme disease to about 13,000 people each year. Economic damage to agriculture, timber, and landscaping by deer totals more than $1.2 billion a year.

The problem, as nearly any suburbanite in the eastern United States knows, is that deer populations are exploding. Researchers estimate that prior to the arrival of European settlers, white-tailed deer numbered between 23 and 34 million. By the early 1900s, deer populations had fallen to between 300,000 and 500,000 animals. This population crash was a result of market hunting, that is, killing and selling the animals to butchers.

In 1900, the passage of the federal Lacey Act, prohibiting interstate traffic in wild game taken in violation of state law, effectively ended market hunting. At the same time, states like Pennsylvania and Virginia established game commissions that restocked deer and prohibited the hunting of does. Before the arrival of settlers, predators like wolves and bears, along with Native American hunters, had kept deer populations in check.

After their nadir in 1900, deer populations began to recover, rising to around 27 million animals today. State game commissions' constituents are chiefly hunters. Since hunters want more deer, these agencies have traditionally managed deer in order to maximize their numbers. This means that until recently, hunters could kill bucks but not does. In some areas, does outnumber bucks 30-to-1.

Deer overpopulation harms natural ecosystems. In high deer density areas, deer browsing prevents the regeneration of forests as deer eat nearly all the tree seedlings, destroy forest understory plants, and reduce overall species richness. Several studies found that deer browsing significantly reduces songbird numbers by destroying their habitats.

So how to protect ourselves from this dangerous mammal? Some more squeamish suburbanites, who generally hunt for their steaks and venison at the local supermarket, suggest using contraception. And in urban settings, contraception does work. "Shooting deer in urban parks and yards is illegal, unwise, unsafe, and publicly unacceptable," says Jay Kirkpatrick, director of ZooMontana's Science and Conservation Biology Program. Kirkpatrick has developed a vaccine using porcine zona pellucida proteins (pig proteins that surround pig eggs) that prompts a deer's immune system to produce antibodies that block egg fertilization. To be effective the vaccine must be injected, usually via dart guns, into deer four to five times over several years.

The vaccine has successfully reduced the number of deer on Fire Island in New York by 50 percent over seven years, and by 40 percent at the National Institute of Standards and Technology campus in Gaithersburg, Maryland, over the past five years. Kirkpatrick notes with dismay that state game commission bureaucrats refuse to use contraception on state-controlled urban lands because their hunter constituents fear that animal rights activists will try to require its use on free-ranging forest deer populations. Kirkpatrick notes that his center makes only 4,000 to 5,000 doses of the vaccine annually and that contraceptive vaccination is totally inappropriate for controlling deer populations on wildlands.

Hunters traditionally want to kill bucks with big sets of antlers. In the past century, state game managers have persuaded hunters to leave does alone to reproduce. However, an innovative program called Quality Hunting Ecology advocated by Brent Haglund, president of the Sand County Foundation in Wisconsin, is being adopted by some states. The idea is that hunters must kill two does before they can shoot a buck. This program reduces the number of fertile females. One apparent side effect of having fewer female deer is that testosterone levels rise in bucks that must compete for access to the remaining females, thus making them bigger trophy animals. Preliminary results of the Quality Hunting Ecology program in Wisconsin show that it does reduce the deer population and improve forest quality. Pennsylvania has just adopted a similar program for this current hunting season.

However, Donald Leal, a senior associate at the Political Economy Research Center in Bozeman, Montana (an environmental think tank), advocates an even more radical solution to the problem of deer overpopulation: a return to market hunting. Leal points out that the chief reason there is a deer problem is that hunters want to maximize their benefits, in this case, the number of deer available for them to shoot. So game commissions have adopted regulations that do that.

Leal is not advocating a return to the open commons that prevailed in the 19th century, which led to the steep decline in deer populations. But Leal does think that a system modeled on individual tradable quotas (used to manage some fisheries) would help keep deer populations healthy and in check. Right now, it is illegal for hunters to sell their excess game to anyone. This prohibition leads to absurdities like the fact that nearly all the venison served in America's finest restaurants is imported from places like New Zealand (where deer are an exotic species). Leal suggests that state game commissions could determine acceptable herd sizes and then sell quotas to hunt to individual hunters, outfitters, and restaurant cooperatives for the excess. Leal points out that his home state, Montana, already sells licenses to hunt bull elk to non-residents for around $1,000.

The political obstacle to re-establishing market hunting by creating a game quota system is that hunters would fiercely oppose it. They don't really want reduced deer herds. But perhaps city dwellers and suburbanites, tired of ramming deer with their SUVs and watching their landscaping be turned into deer pellets, will one day be able to outvote the hunter lobby and restore market incentives to managing wildlife. Then Bambi will no longer kill so many people and cause so much damage to our forests.