Killing programs aimed at reducing deer populations are often controversial, difficult to execute safely in urban and suburban areas, and don't result in long-term population reduction. Wildlife fertility control offers a humane way to manage deer populations where necessary and appropriate.

PZP (porcine zona pellucida) is an immunocontraception vaccine that can be used to control fertility in adult female deer and other mammals. Unlike some fertility control vaccines and methods that can cause undesirable behavior changes, PZP simply prevents fertilization from occurring. Most importantly, because PZP is a natural protein, like all other proteins found in animals, it is safe to use and will not harm animals. PZP can be delivered to adult female deer by hand or remotely using darts shot from a dart gun.

Recent improvements in the PZP vaccine now prevent deer from having fawns for up to three years with just one treatment. These vaccines significantly reduce the time needed to dart animals and, more importantly, reduce the costs of treating deer.

Since the 1990s, the HSUS has conducted several successful PZP immunocontraception research projects on deer. The biggest and most successful have been at Fire Island National Seashore (FINS) in New York, on Fripp Island in South Carolina and at the National Institute of Standards and Technologies (NIST) in Gaithersburg, Md.

Fire Island National Seashore was the HSUS's original deer study site. The primary goals there were to see how effective PZP was in deer and whether or not more than 200 of them could be darted each year. Both were easily accomplished, but more importantly, we found immunocontraceptives alone could be used to stabilize and reduce a deer population over time.

Recent improvements in the PZP vaccine now prevent deer from having fawns for up to three years with just one treatment.

The HSUS has also been using PZP to treat the deer population at NIST for 20 years. During this time, the number of deer collisions has dramatically decreased, the remaining deer have become healthier and the deer population growth rate remains low, despite the fact that urbanization and development around the facility results in constant migration of new deer into the facility's deer population.

The immunocontraception study on Fripp Island, S.C., has been the most successful. Over a five-year period, the deer population decreased by nearly 60 %. In addition, residents of Fripp Island are very pleased by the results, happy to see that the remaining deer population on the island is healthier and causing fewer conflicts.

Surgical sterilization

Sterilization programs are another option for humanely controlling the population growth of white-tailed deer and although sometimes cost-prohibitive, recent programs have shown great results.