QUESTION: After reading several recent articles about states and municipalities using contraception as a method of deer population control in urban areas, do you know if there have been any studies indicating whether or not these methods actually work? -- D. Berry of Pensacola, Florida
ANSWER: Contraception is one non-lethal method managers have tested to control "problem" deer populations, typically in urban or suburban areas.
There are three methods, surgical sterilization and application of either synthetic hormones or immunocontraceptives (ICs).
Surgical sterilization is permanent, but extremely expensive and not practical under field conditions. Hormones and ICs are largely considered ineffective for several reasons. They are expensive.
Studies have shown the treatment cost per deer ranges from $600 to $1,000, or higher. This cost must be borne by taxpaying citizens, and becomes even less appealing when you consider deer populations can be reduced by lethal means (hunting) at virtually no cost (there's actually a net benefit through the sale of licenses and permits).
In order for them to be an effective population control, you have to treat a significant (70-90 percent) of the deer in the population, which isn't always practical or feasible.
A Connecticut study concluded, "... even with good access to a relatively small and isolated free-ranging deer population (about 30 females), an adequate number of female deer could not be successfully treated to limit population growth.
Even an adequate treatment rate does not account for emigration of fertile deer into the area from surrounding areas.
Only surgery is permanent.
Other methods, like ICs, are temporary and require re-annual or bi-annual application or boosters, which involves more cost, and requires a similar treatment rate to be effective.
Last, but certainly not least, the FDA has approved the use of ICs only under tightly regulated experimental conditions.
ICs have not been approved for general use, and that isn't expected to change in the near future.
There is also a logical argument against the use of ICs. The principle reasons for controlling deer populations is to reduce or eliminate crop and property depredation, deer-vehicle collisions and the transmission of diseases like Lyme disease and human Erlichiosis. Non-lethal controls prevent or suppress deer population growth. But because some deer remain, the potential for all of the above conflicts remains as well, which begs the question, why bother?