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Birth Control for Deer?

By Matthew Schuerman

posted 2/8/02

If all goes as expected, no more than 30 fawns will be born on the inhabited end of Fire Island this spring. That compares to some 300 that would have been born a decade ago. No, there's nothing in the water. The adult does are being treated with a contraceptive vaccine that, slowly but surely, is working.

The vaccine, now in its experimental stage, comes none too soon. Deer have overrun suburbs across the country, spreading Lyme disease and destroying gardens and denuding trees that might otherwise shelter birds. But in densely populated areas, hunting is too dangerous or too unpopular, which is why the Humane Society of the United States got into the birth control business.

Every fall since 1993, researchers have ridden mountain bikes along Fire Island's boardwalks, shooting vaccine-laden darts into unsuspecting does. The vaccine, made of pig proteins, renders the animal infertile for the rutting season. The darts also splatter red-vinegar dye on the doe's rump to indicate that she has been treated.

The Humane Society jumped in after a disastrous archery hunt left deer wandering the boardwalks with arrows sticking out of their rumps. As a result, it never did get the sort of base count needed for a truly scientific study. But Brian Underwood, a biologist evaluating the project for the U.S. Geological Survey, says that in the section his team has been studying the longest, the deer population has fallen by more than half, from an estimated 128 in 1998 to 59 in 2001.

But Fire Island is the success story: Its 10 percent birth rate contrasts to 35 percent at other Humane Society sites. Getting darts in the animals in the first place is an obstacle, and particularly difficult in areas where hunting has been allowed. "If you can get at the females and deliver the vaccines, it will work," Underwood says. "There are plenty of pen studies that show it will work."

That means people will have to be patient, and not everybody is. One Humane Society project in Connecticut was cut short after just three years when residents wearied of the results. Nine out of 21 does there had given birth that spring--though, to be fair, most of the new mothers had not been treated, because they were part of the control group. One of the villages involved, Mumford Cove, opted for a hunt instead--and brought its deer population down by 92 percent in six days in the fall of 2000.

It could take another 5 to 10 years to perfect the vaccine and win approval from government regulators for commercial sale. But the Humane Society's labor-intensive method--which costs about $1,000 per doe for the first two years of treatment--may keep it from widespread use. A serum that lasts longer than one rutting season is in the early stages of development; if successful, it could bring down costs. Lacing deer food with oral contraceptives is another possibility, according to Dwayne Kirk, project manager at the Boyce Thompson Institute in Ithaca, New York, which is experimenting with genetically modified tomatoes, potatoes, carrots, and alfalfa in powdered form. But while some detractors suggest that squirrels and other animals could become infertile through eating the bait, Kirk says scientists have the tools to design species-specific contraceptives.

Larry Katz, an associate professor of animal science at Rutgers University, is skeptical of the whole idea of deer birth control, though he still thinks it is worth researching. "I fully support that we go out and try it in places, and I recommend that the investigators very carefully categorize the cost per deer and how effective their efforts are," he said. "But ultimately, we are going to have to make economic decisions."

People will also have to make emotional decisions, and that is why immunocontraception researchers think their products will find a market. A group of residents in Princeton, New Jersey, almost blocked a private sharpshooting firm from removing deer in their town this winter, and a Rutgers University poll (not conducted by Katz's department) found in January that half of New Jersey residents believed an animal's life to be "as sacred as a human being's." *

Underwood, the government evaluator, puts it this way: "The differences in results between culling and a humane program are substantial, but there are values attached to each one that people are willing to trade off. Is it worth waiting [for an effective contraceptive]? Depending on whom you ask, yes."

* The sample size was 500 people; the margin of error was +/- 4 percent.