The state of “Deer Contraception”: January 2010 Update


Fairfield County Deer Management Alliance
The Myth that “Deer Contraception” reduces numbers of wild deer: January 2010 Update

“Does contraception have a role in deer population management?” Or- “Why don’t we just use birth control on the deer?”

These are questions that frequently arise from the general public in conversation about the deer problem.

Many communities in our area are grappling with the issues surrounding white-tailed deer and the problems that occur when deer and humans interact. Increasing numbers of both species cause increasing problems, in particular Lyme disease, deer-vehicle accidents and environmental devastation due to over-browsing of the woodlands.

The possibility of altering fertility in wild animal species has existed since around 1985, using sterilization, contraceptive drugs and more recently vaccines that prevent conception. Vaccinating against conception is known as immuno-contraception The first immuno-contraceptive vaccine developed required two shots before the antibody levels were high enough to be effective and it required an annual booster. The shots have to be delivered by trained marksmen and the treated deer must be tagged so that they can be identified for subsequent booster doses. In wild deer this tagging requires capturing and sedating each deer. So while the vaccine might cost as little as $10 a shot, the injection of the deer typically costs $500 to $1000 per shot.

A less labor intensive and therefore inexpensive way of treating the deer might be to give a drug by mouth via a food product such as a salt lick. However contraceptives are not yet species specific and might be taken up by any wild animal in the woods. The substances would then enter the food chain and have untold effects on multiple species, including humans. Thus the idea of an "oral contraceptive" is currently impossible.

Moreover, injectable vaccines are still only available as part of a controlled drug trial approved by the FDA and Department of Natural Resources. It was initially used to keep the wild horse herd under control on Assateague Island in 1994, and has successfully been used in elephants in Africa and in a variety of animals in zoos.

The National Wildlife Research Center has since conducted research with the vaccine on the white-tailed deer and the coyote. All of the studies with deer contraception required strict protocols and acceptance of the study conditions by the DNR. An article in October 2007’s issue of Smithsonian Magazine discusses all the issues associated with deer overpopulation and describes the experimental studies at National Zoo in Washington DC.

The results of all these studies in deer have shown that only isolated herds can be managed in this way. According to the DEP the difficulty of darting the same deer repeatedly with boosters makes this very time consuming, difficult and therefore expensive. The most promising drug in 2007, SpayVac™ was withdrawn from studies due to failure in trials. The drug's failure in New Jersey and Ohio, according to company officials, resulted from a change in the manufacturing process needed to meet the federal Food and Drug Administration's sterilization standards. ImmunoVaccine Technologies Inc. of Nova Scotia, which owns the patent and rights to manufacture SpayVac, has stopped funding the project.

The newest immunocontraceptive drug under study, GonaCon, has a longer duration of effectiveness but is still only under 50% effective during the second year in field studies. This will unfortunately leave enough fertile deer to keep the herd growing and not result in any decrease in free-ranging deer populations.

A single hand-injected dose of GonaCon has successfully kept some female deer infertile for up to 5 years in pen studies. During field studies in New Jersey and Maryland using free-ranging deer in semi-enclosed urban settings (partially fenced), the vaccine was 67-88 percent effective at preventing pregnancy the first year and 47-48 percent effective the second year. A second dose is recommended during year two to extend contraceptive effectiveness. Based on available data, it is unclear how often deer will need to be re-vaccinated to maintain infertility in subsequent years.

GonaCon has not been tested with large, free-roaming populations of white-tailed deer. Modeling studies have been done that investigate the long-term population effects of contraceptives to prairie dogs, but not deer (See
GonaCon was officially registered by the U.S. Environmental Protection Agency on September 29, 2009 for use with female white-tailed deer. Its EPA reg. number is 56228-40.

GonaCon is registered as a restricted-use pesticide, and all users must be Certified Pesticide Applicators. Only USDA Wildlife Services or State wildlife management agency personnel or individuals working under their authority may use it. In order for GonaCon to be used in any given State, it must also be registered with the State and approved for use by the State fish and game/natural resource agency. More information can be found by contacting USDA Wildlife Services' Connecticut State Director Monte Chandler at 413-253-2403 for more information.

GonaCon is available for purchase from NWRC starting January 2010; however, use might be delayed pending registration and approval in specific states.

EPA approve drugs on the basis of their environmental safety and non target issues, not on their effectiveness as a population control drug. So EPA approval and registration should not be interpreted as an endorsement of its use to control deer herds. Its best effect is measured on a group of treated deer in a fenced or partially fenced area- and not on the reproductive capability of a wild herd, some of which will not have been treated at all.

Why birth control cannot work on Connecticut’s deer

Contraception cannot reduce deer numbers initially for many years, if at all. Deer live for up to 15 years and will continue to cause woodland damage, spread Lyme disease and cause car accidents even if they are made temporarily infertile. According to the DEP, and the USDA, the difficulty of treating enough deer in a free ranging herd is overwhelming: the percentage of does requiring treatment is very high (90%) and we have an estimated 150,000 deer in CT! That would cost $135 million every 2 years and require the successful explosive darting of 135,000 deer with 100% efficacy of the drug. Since GonaCon is only 88% effective at its best, even in the first year, it is mathematically impossible to treat enough deer for this to be effective.
There are also unwanted effects on deer behavior, on deer social structure, and some long term health effects on the deer such as ovarian and bone marrow abnormalities. Unless birth control agents can be developed that are species specific and work through the animal’s digestion system, thus can be added to foods, the cost of treating each female will be high-it was over $1100 for the now shelved SpayVac.

Other approaches that have been considered include surgical or chemical sterilization of large, dominant male deer which are then kept in the population. This is being studied in North Branford, CT in areas with deer populations of 120/square mile. However the researcher herself , Uma Ramkrishnan, admits that “sterilization must be viewed only as a long term solution and is unlikely to be more effective than hunting” and with field populations, it would never be possible to capture and treat all the individual deer so this could not work in practice.

The following Q/As are from the USDA Wildlife site on GonaCon:

Q. Who will be allowed to use GonaCon?
A. GonaCon is registered as a “Restricted Use” product. NWRC says the product is labeled for use by state or federal wildlife or natural resource management personnel or persons working under their authority. GonaCon users will need to follow state authorization processes.

Q. Will GonaCon eliminate the need for hunting to control deer overpopulation?
A. No. Contraception alone cannot reduce overabundant deer populations to healthy levels. GonaCon is a tool to be used in conjunction with other wildlife management methods.

Deer management through contraception is still experimental in free-range deer herds. The availability of GonaCon is not an endorsement of its effectivenss at the population level, merely its lack of toxicity. Attempts to make the SpayVac vaccine safe and effective failed in trials. The similar GonaCon is being released in in 2010 for restricted use, but it has very limited efficacy and will not reduce deer numbers without prior lethal culling. Managing free ranging deer populations presents problems not found with isolated deer herds. It must be remembered that even if more effective fertility control were to become available, it has no short-term effect on population size, hence pre-treatment culling would be an essential part of herd reduction, with the fertility control used to maintain the lowered deer density. The myth that contraception that can reduce deer herds is an available option is unfortunately delaying any real action in controlling deer numbers in many communities.

GonaCon: U.S. Department of Agriculture
Animal & Plant Health Inspection Service
Wildlife Services
National Wildlife Research Center
4101 LaPorte Avenue
Fort Collins, Colorado 80521-2154

PZP: for PZP vaccine diagramatic explanation and study data

Connecticut Department of Environmental Protection discusses contraception on page 6 of a booklet entitled “Managing Urban Deer in Connecticut”.
Deer Management

Spayvac™-for-wildlife's explanation of FDA requirements for approval and problems involved:

New York Times "Putting Nature on the Pill” Aug 31 2004

Smithsonian Magazine Vol 36 No 7 Oct 2005 “Oh Deer” by Anne Broache

New Jersey Ledger, September 18 2007 “Deer Contraceptive Fails in Jersey Test” by Brian Murray:
SpayVac seemed to be the answer and the state allowed a test program this year after an early version of the vaccine used at Penn State University three years ago showed promise. Despite regular mating, none of the test deer in that experiment has become pregnant.

The drug's failure in New Jersey and Ohio, according to company officials, resulted from a change in the manufacturing process needed to meet the federal Food and Drug Administration's sterilization standards.