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Bambi ate my rhododendrons

The growing cost of an ecological imbalance

November 5, 2007
The Altoona Mirror

By Nat Gillespie

For much of the 19th century, wildlife managers worried there were too few white-tailed deer. They adopted game laws, outlawed market hunting, and enforced a disciplined public education program to protect does in order to revive this animal from near extinction.

The tables have clearly turned. Deer populations have mushroomed across America. From a low estimated at 50,000, they now exceed 30 million.

Deer adapted remarkably to the highly modified environment created by residential development. They thrived at the edges of woods and on nutritious landscaping. Now humans struggle to adapt to numerous conflicts with white-tails and the deer’s rattling comeback is underscored by the increasing public characterization of this resilient ungulate as “pest” rather than “Bambi.”

Considering the development projections for the Chesapeake region, conflicts with humans will likely increase. Already, with the removal of wolves and mountain lions and the decreases in hunting, cars have risen in the ranks of predators. State Farm Insurance estimated that in 2006, deer/car collisions caused 200 human casualties and over $1.1 billion in damage.

Aldo Leopold, considered the father of modern conservation, researched deer population dynamics and documented their prodigious capacity to multiply. In one study in Southeastern Michigan, Leopold reported that a group of 2 bucks and 4 does placed in an enclosed reserve proliferated to 160 animals in only 6 years.

George Timko, an urban deer biologist whose position was created in response to increasing deer complaints in Maryland residential areas, noted, “Many of these local populations far exceed healthy ranges of deer numbers, often 10 times that density. In the most extreme example, densities of over 300 deer per square mile were documented, and (densities) often exceed 100.”

Impacts are not limited to human property. When considering the massive changes to ecosystems generated by little creatures such as zebra mussels, it is not far-fetched that a species whose palate includes hundreds of native plants could transform the mid-Atlantic’s forests. In fact, at a density of 20 per square mile, scientists have found that deer can quickly change a forest’s composition.

The State of the Chesapeake Forest, a recent report by The Conservation Fund and the United States Department of Agriculture Forest Service, found that “by selectively feeding on certain plants, deer overbrowsing can change forest composition. Shifts in forest plant communities, in turn, affect wildlife species that depend on this vegetation for food and shelter.”

Continued overbrowsing in the northern Chesapeake forests could produce near monocultures of plants resistant to deer browse. In Pennsylvania more than “50 percent of all forests lack sufficient numbers of seedlings and saplings to replace the existing forest with a similar tree composition,” the report found. It noted that oak trees, in particular, are not regenerating and warned that “If deer control is not increased, more than 60% of desirable timber species will not be available to the Pennsylvania timber industry.” Though the situation is direr in Pennsylvania, the report said forests throughout the region face similar impacts.

Loss of forest understory also means more raindrops hit the forest floor, increasing water runoff and erosion, further degrading the region’s streams. Over-abundant deer also frequently eat newly planted streamside buffers before they can take root.

“What people need to realize is that current deer populations can have real water quality impacts in local watersheds, and potentially across the Chesapeake Bay watershed as forest understory diversity and abundance disappears,” said L. Douglas Hotton, deer project leader for Maryland

Effective deer management has no silver bullet, however, wildlife managers point to the bullet as the most effective tool.

“The first challenge is to reduce the size of the herd,” said Timko, “and to do that, antlerless deer must be removed from the population. Managed hunts, sharpshooters, and bowhunting can be effective lethal methods but require site-specific application.”

While some support contraception, constraints exist. In addition to significant time and funding costs, research from University of Michigan and University of Wisconsin on intra-uterine device contraception for deer reveals that nature works quickly to favor reproduction. Unsterilized females face less competition for resources and reproduce more successfully, and fawns then survive and reproduce themselves more successfully. At best, contraception represents a temporary solution.

At the household level, fencing can protect landscaping and trees, but most repellent techniques are ineffective. Timko remarks, “white-tailed deer have proven to be very adaptable creatures and have learned that people and even their dogs are largely benign. I know of deer setting up in someone’s backyard and chasing the dog back inside.”

In the landscape we have created, these new cohabitants appear likely to stay. We had better realize that the boom in Bambis may ultimately bear far greater systemic costs than losing the patio’s rhododendrons.

Nat Gillespie is a scientist at Trout Unlimited and lives in Washington, D.C.

Distributed by Bay Journal News Service

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