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Overpopulation problems

December 20, 2010
By GEORGE J. BRYJAK, Special to the Enterprise

Oh, Deer! A series about deer population, Part 2 of 3


Deer can exist in a variety of environments; however, they prefer (and thrive in) border or "edge" regions between woods and grasslands. At a forest's edge, sunlight and ground vegetation are abundant; deer can browse in open areas and quickly retreat to the forest at the first sign of trouble.

Article Photos

Deer favor forest-edge places like this, where sunlight and ground vegetation are abundant. They can browse in open areas and quickly retreat to the forest at the first sign of trouble.
(Enterprise file photo — Lou Reuter)

The suburbanization of America has created deer-friendly edge areas with woods, water, manicured lawns, flower and vegetable gardens - what one observer calls "ready-made deer parks." Greater Washington, D.C., bounded by heavily deer-populated Maryland and northern Virginia suburbs, has been dubbed the "ultimate salad bowl for deer."

While the "deer caught in the headlights" phrase speaks of a stupid creature unable to act decisively, these animals are hardly on the bottom rung of the intelligence ladder. Some biologists are of the opinion that suburban deer learn to anticipate the time when garbage is collected, when school buses stop, when people walk their dogs and when they return from work. Evidence suggests that many deer are capable of determining which land is hunted and which land is safe, and move to the latter. Leonard Lee Rue argues that while deer intelligence does not begin to compare to that of coyotes, "Some deer have more reasoning power than we give them credit for."

In her Washington Post article, "Dear Heaven," Liz Mundy argues that by way of suburbanization, "We may be driving deer evolution, creating an animal that is not only attracted to suburban areas, but adapted to live easily within them." She quotes Auburn wildlife biologist Steve Ditchkoff, who argues that the urban-suburban deer is already "a different creature than we find walking about in rural areas."


Too many deer?

A deer population with adequate food and no predators will increase rapidly. In 1928, two bucks and four does were placed in a 1,200-acre tract in southern Michigan surrounded by an 11-foot deer-proof fence. Six years later, there were at least 160 deer on this land. A study in Nebraska found that 90 percent of does impregnated when less than a year old gave birth to a single fawn, with 10 percent having twins. Sixty-seven percent of older does had twins, 21 percent gave birth to a single fawn, and 12 percent had triplets. The proliferation of deer across much of the country has resulted in a number of problems.


Motor-vehicle accidents

The Insurance Information Institute reports there are approximately 1.5 million deer-vehicle accidents a year (vehicles hitting deer, deer hitting vehicles and drivers involved in accidents by way of losing control of their vehicles attempting to avoid hitting deer). In 1993, 101 people died in crashes involving animals (mostly deer). That number increased to 150 in 2000 and 223 in 2007. In addition to fatalities, tens of thousands of people are injured in these encounters. Deer-related accidents are most likely to occur in October and November when bucks are chasing does (sometimes for miles) and in the late spring and early summer when fawns begin to follow their mothers.

The annual repair cost of deer-vehicle accidents is approximately $3.6 billion a year (about $3,000 per incident) with another $1 billion for medical expenses and out-of-pocket costs to drivers. Wisconsin Commissioner of Insurance Jorge Gomez states that "many people are not aware that the collision coverage under an automobile insurance policy does not cover you if you hit a deer." Only comprehensive insurance pays up in such accidents. The five states with the highest deer accident count in the 2007-08 fiscal year were Michigan (104,676), Pennsylvania (102,166), New York (80,022), Ohio (66,353) and Virginia (54,135).

Calculating the odds of being involved in a deer-vehicle accident - that is, the number of such accidents in 2007-08 in relation to the number of registered vehicles - a West Virginia motorist had a one-in-39 chance while a New York driver had a one-in-141 chance of being so involved. The national likelihood of a deer-related vehicle accident in 2007-08 was one incident per 209 drivers.


Lyme disease

The relation between deer, ticks and Lyme disease is controversial. Almost 250,000 cases of this malady were reported to the U.S. Centers for Disease Control between 1992 and 2006 by health departments in all 50 states, the District of Columbia and U.S. territories. The incidence of Lyme disease increased from just under 10,000 cases in 1992 to almost 20,000 in 2006 to approximately 29,000 cases in 2008. According to entomologist Kirby Stafford, Lyme disease is significantly under-reported "and these numbers may represent only 10 to 20 percent of diagnosed cases."

In 2002, 12 states accounted for 95 percent of reported cases. In order of incidence per 100,000 population, these states were Connecticut, Rhode Island, Pennsylvania, New York (especially in the Hudson Valley and Long Island), Massachusetts, New Jersey, Delaware, Wisconsin, Minnesota, Maine and Maryland. All of these states have significant deer populations. The CDC reports that while deer do not become infected with the bacterium that causes Lyme disease, they are a major source of the blood that adult ticks need to reproduce.

As deer are a primary food source for ticks that cause Lyme disease, many observers are of the opinion that reducing deer populations will translate to a decrease in the number of individuals who contract this malady. Some studies have concluded that when deer populations are reduced, the incidence of Lyme disease declines. The CDC reports that while studies in coastal locations found that reducing the number of deer generally decreased the number of ticks, the level of deer reduction required to break the cycle of Lyme disease "was not established."

Biologists Felicia Keesing and Richard Ostfeld reject the tick-Lyme disease connection, noting that studies in New York and New Jersey found no correlation between the number of deer and the number of ticks in a region. These researchers argue that when deer are scarce, ticks simply move to alternate hosts: raccoons, skunks, opossums and other medium sized animals. Keesing and Ostfeld note that Lyme disease is rare in Southeastern and most Midwestern states, regions of the country where deer are plentiful.


Destruction of the environment

University of Minnesota ecologist Lee Frelich believes there is a "broad scientific consensus" that deer are causing "significant" damage to forests across the Midwest and Eastern states. Wisconsin biologists calculated that deer in their state cripple or eliminate over 600 million tree seedlings annually.

Richard Parker of the Genesee State Park Region (New York state) notes that "deer eat anything and everything. ... There are no saplings, no underbrush for ground nesting birds." As long as deer populations remain high, "there will be no regeneration of the forest. In 40 to 50 years as the present forest dies there will be nothing to replace it."

George Timko of Maryland's Wildlife and Heritage Service notes that deer will nibble shoots from plants until they no longer have the wherewithal to grow, culminating in a "dead forest that will not replace itself." In areas of high deer concentration, there are feeding or "browse lines" below which vegetation is scarce.

Emile DeVito of the New Jersey Conservation Foundation believes that as a result of rapidly growing deer populations, "our native forests and associated bio-diversity will melt away."

(A National Geographic article on the significant decline of some bird species in England, another country with an escalating deer population, concluded that "Britain faces a stark choice: Bambi or the birds.")

Deer degradation of the natural environment also comes at a significant monetary cost. According to one estimate, deer cause at least $750 million in damage annually to the nation's timber industry. Paul Curtis, wildlife specialist at Cornell University, states that deer-related damage to New York's annual agricultural harvest costs farmers between $58 million and $60 million a year.


George J. Bryjak lives in Bloomingdale after teaching sociology for 24 years at the University of San Diego. A list of sources will accompany the third and final part of this series on deer.



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