For the first time in 33 years, New Jersey is allowing hunters to thin out its burgeoning black bear population. Animal-rights activists have assailed the six-day hunt, arguing that the state should sterilize the bears instead. How, exactly, does one sterilize a black bear in the wild?

There are two proposed methods, neither of which has been tested on wild black bears. The New Jersey Animal Rights Alliance believes the short-term solution is Neutersol, which the Food and Drug Administration has approved for the nonsurgical sterilization of puppies. The drug must be injected into the testes, so the bears would have to be sedated and anesthetized for the procedure. Winter would be an ideal time to administer the Neutersol since a hibernating black bear is much easier to medicate than a frisky one. The NJARA estimates that each chemical sterilization would cost between $80 and $100, a tab the group would pick up with the assistance of the antihunting Bear Education and Resource Group. The ultimate goal would be to fix the majority of New Jersey's 3,000-plus black bears.

        State wildlife officials, however, are skeptical of the Neutersol approach. They've pointed out that the drug has yet to be tested on bears, so the correct dosage is unknown, and no one even knows whether it can effectively shrink ursine testicles. "I fail to see how injecting an untested chemical, at speculative doses, into the testes of our majestic black bear population could possibly be considered humane," said Bradley M. Campbell, commissioner of the New Jersey Department of Environmental Protection, in a September statement.

        The state is far more intrigued by porcine zona pellucida, the membrane that covers the eggs of female pigs. When PZP is injected into a female of another species, the animal's immune system treats it as a malicious invader and produces a raft of antibodies. These antibodies cluster around the animal's egg, preventing sperm from entering. PZP has already been used successfully as a prophylactic on white-tailed deer in Ohio and on wild horses in Nevada, as well as on 25 black bears at a South Dakota tourist attraction called Bear Country U.S.A. Unlike Neutersol, PZP needn't be injected into a particularly sensitive and hard-to-reach part of the body, and animals don't need to be tranquilized to receive a dose. PZP can be shot into an animal's butt or hip via a 3-inch dart, which drops away from the skin once the medicine has been administered. The one drawback: Each PZP dose only lasts a year while Neutersol, if it worked on bears, would be permanent.

        The New Jersey DEP is partnering with the Humane Society to study PZP's effectiveness in wild black bears. But there is no timetable for when the contraceptive might replace the hunt as the state's preferred population-control method.