Animal rights activists promote the development of new experimental technology called immuno-contraception or birth control for wild animals as opposed to culling or hunting as a means to control over-population of species. The contraceptive agent is injected into the animal either by blowdart or after the animal is tranquilised, usually requiring a follow up booster shot several weeks later, with the process repeated each year.
The US National Park Service and Humane Society have been experimenting with immuno-contraception on the deer population at the Fire Island National Seashore since 1993. Two or more years of vaccinations have reduced pregnancies in treated animals by 85 to 90 percent, significantly slowing the growth of the herd.