Bambi on Birth Control

The biggest challenge to managing animal populations with contraceptives may be getting people to agree about it

By Jennifer Weeks

The benefits of wildlife birth control are obvious. PZP, for instance, has played an important role in reigning in the herd of wild horses on Assateague Island, a barrier island located off the coast of Maryland (see sidebar). “PZP has exceeded every expectation and is a wonderful management tool. I don’t know where we’d be without it,” says Carl Zimmerman, a resource management specialist with the National Park Service at Assateague Island National Seashore. “There are no signs of harm to the horses, it doesn’t appear to change their behavior or social interactions, it’s relatively easy to use, and the cost is reasonable.”

But Kirkpatrick says that the vaccine won’t work in every setting. “PZP was developed to control localized deer populations in urban areas where traditional lethal methods are no longer legal, wise, safe, or publicly accessible,” he says. More remote areas such as California’s Point Reyes National Seashore, where exotic fallow and axis deer are overgrazing the park and competing with black-tailed deer and other native animals, are another matter. There, the Park Service has hired sharpshooters as well as agreeing, under pressure from activists, to use contraceptives to regulate about 1,100 female deer. “Contraception won’t succeed at Point Reyes because the deer are wild and getting to them is going to be very, very difficult,” Kirkpatrick says.

The difficulty is that finding the creatures in the wild and delivering the contraceptives at close range with a dart gun is both costly and time consuming. These challenges, combined with strong hunting traditions, have made some states reluctant to adopt animal contraception.

Animal-rights advocates, meanwhile, say it’s people, not animals, whose behavior needs to be modified. “When we use birth control on free-ranging animals it’s usually to create new opportunities for consumptive users—for example, sterilizing wolves in Alaska to support deer and moose hunting,” says Priscilla Feral, president of the nonprofit Friends of Animals. “We need to carve out more habitat for wildlife, but it’s outrageous for people to determine that deer and horses and geese and squirrels should all be subject to birth control.”

Sometimes compromise is possible. Mainstream environmental groups including the Audubon Society and the Sierra Club have endorsed hunting, either instead of or in combination with birth control, in places where animals are seriously harming ecosystems or spreading Lyme disease. Under New Jersey’s community-based deer management program, many towns have adopted a combined approach that includes using contraception, hiring professionals to capture or shoot animals, opening off-limits lands to hunters, and lengthening the hunting season.

Finding solutions that work are imperative because the problem isn’t going away. “Urban wildlife issues are getting bigger and bigger, and the questions aren’t about science—they’re political, social, and cultural,” says Kirkpatrick. “That’s the expertise we need to solve these problems.”

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When I lived in Berkeley, the city decided to trap and sterilize squirrels in order to control the exploding population. I worked at a newspaper at the time, and we had loads of fun coming up with off-color (and, of course, unused) headlines for that one.

TNR is probably a better option than hormonal birth control, at least with populations of wild animals that aren't endangered.

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