Deer: Contraception

CONTRACEPTION
(Not supported by IDNR in free-ranging contexts.)

Two primary forms of contraception have been utilized to stem the growth of deer herds: PZP and GnRH.

The first method of inducing infertility in deer is by immunocontraception using a vaccine extracted from the ovaries of pigs, called porcine zona pellucida (PZP), in which the deer is immunized against a protein or hormone needed for reproduction (Miller and Killian 2000). When this vaccine is injected into a doe, her immune system forms antibodies against the vaccine. After the doe ovulates, the vaccine antibodies attach to her ovum and block fertilization, which causes the female to experience multiple estrous cycles and extends the breeding season (Warren 2000). An extended breeding season will increase deer activity at a time of year when conservation of calories is important and may result in increased winter mortality. Lengthened breeding activity of bucks may also lead to an increase in the number of deer-vehicle collisions. At this time, the use of PZP for fertility control in deer is experimental.

Unlike PZP, GnRH prevents eggs from being released from the ovaries, thereby eliminating multiple estrus cycles. GonaCon™ is the only commercially-available approved GnRH vaccine. Long-term field efficacy data does not exist; however pen studies (wherein animals are confined and excluded from other deer) indicate that a single-shot GnRH vaccine can last for up to four years (Miller et al. 2004). The EPA has approved the use of GonaCon™ as a "pesticide." However, the Office of the Indiana State Chemist has not approved this pesticide for use in Indiana. At this point, there are no known dangers to humans or wildlife from eating deer vaccinated with GonaCon™. However, the long-term bioaccumulative effects of the pesticide are still being studied.

EFFICACY: As a stand-alone management strategy, contraception does not reduce overabundant deer populations. A number of factors shape the efficacy of contraception.

· Deer Population Must Be "Closed." Treated deer populations must be isolated, or closed, from adjacent populations. Deer immigration from adjoining properties would negate any fertility control efforts within the treated area, as new immigrants have not been exposed to the fertility agents.

· A High Percentage of Does Must Be Treated. A large proportion of the females (70-90 %) must be treated to curb or reduce population growth.

· Population Must Be At Target Level. Since mortality rates for suburban deer populations are usually low, eliminating reproduction within the deer herd will not reduce total deer numbers for several years after initiating the anti-fertility program. Therefore, a deer population should be at the desired level before initiating this technique.

· Population Growth and Damage. Again, this method is not intended to, nor does it effectively address, immediate population growth or damage concerns.

· Deer Stress. Federal regulations require that GonaCon be administered by hand. PZP is not commercially available and is not subject to specific limitations as it experimental in nature. Use of PZP would require a research permit. IDNR advises that the conditions of any permit would require that the deer be tagged. Both tagging and administering the contraceptive agent by hand requires that deer be captured before the vaccine is administered. Deer are stressed in the capture/trapping phase.

COST: $600-$800/doe, plus ongoing maintenance.

SAFETY: Generally safe, but see above.

MAINTENANCE: Some forms of immunocontraception require boosters. Unless located in a closed system, does immigrating into an area would require dosage.

HUMANENESS: Because this method works by decreasing fertility rather than increasing mortality rates, this method is generally considered humane.

IDNR: IDNR does not support the use of contraception in free-ranging environments. See, IDNR's response to Ogden Dunes, Indiana's request to use GonaCon™ in a free ranging environment (01 August 2012) -- attached on the right side of this page.

TASK FORCE POSITION: Because this technique is not approved by the IDNR in free-ranging environments, and because it is costly, requires that the deer population be closed and the bioaccumulative effects are not known, this is not a viable option.