The University of California Davis wants to give squirrels a lesson in safe sex, and the U.S. Department of Agriculture (USDA) wants to help.

After a particularly frisky population of eastern fox squirrels started reeking havoc on campus trees, buildings and electrical wires in June 2008, researchers at UC Davis contacted the USDA’s National Wildlife Research Center (NWRC).

The researchers, largely in the Department of Wildlife, Fish and Conservation Biology, were interested in conducting a field study to test the effectiveness of GonaCon, a single-shot, multi-year immunocontraceptive vaccine for mammalian species.

Originally developed to help control the white-tailed deer population, GonaCon has also proven effective as birth control for elk, wild horses, feral dogs and cats, prairie dogs, ground squirrels, bison, wallabies, and feral pigs.

The squirrels are captured in humane traps set around the trees where they live, then they are injected and set free.  The vaccine works by blocking the production of gonadotropin-releasing hormones. (For those of you not majoring in biology, that means it prevents the production of sperm in males and ovulation in females.  All sexual activity is decreased as long as a sufficient amount of the vaccine is present in the animal’s system.) While there is no long-term field data about the shot, in pen studies GonaCon kept female deer infertile for up to five years.

Besides taming the libidos of amorous animals, GonaCon is virtually side effect-free. According to Gail Keirn, public affairs specialist for the USDA, it has received positive feedback from private citizens, businesses, and environmental groups interested in nonlethal animal management tools.  For the moment, though, squirrel copulation carries on unchecked. GonaCon is not yet registered by the Environmental Protection Agency (EPA), so current studies are conducted under “Experimental Use” permits.

“NWRC is currently involved in preliminary discussions with UC Davis professor Dr. Dirk Van Vuren,” says Keirn. “Before any studies can take place, an official protocol must be developed and approved by UC Davis and NWRC. The data being collected will support the future registration of the vaccine.”

Other studies on similar species have been conducted at Clemson University in South Caroline (gray squirrels); Berkeley, California (California ground squirrels); and Fort Collins, Colorado (prairie dogs). Keirn says that the USDA hopes to soon submit data to the EPA to support the registration of GonaCon in managing white-tailed deer populations. She predicts that once GonaCon receives its EPA registration, it will be available as a “Restricted Use” product for use by state or federal wildlife or natural resource management personnel.

After receiving the registration for use on deer, it’s likely the NWRC will pursue registration for other species, including impassioned rodents in California. Because when squirrels go wild, they should at least use protection.