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  1. GnRH Agonists - Gonadotropin Releasing Hormone Agonists are considered the safest reversible contraceptives, but duration of efficacy can be unpredictable. To date, data for carnivores indicate time to reversal is extremely variable, with time from implant insertion to birth of offspring ranging from 1-6 years. However, there appear to be trends within carnivore groups showing some taxa reversing more quickly on average than others. Side effects are generally similar to those associated with gonadectomy, especially the potential for weight gain unless diet is controlled.
    Suprelorin® (deslorelin) Implants (F or M)
    Lupron®® Depot Injection (F or M)
  2. Ovariohysterectomy or Ovariectomy - are safe and effective methods for preventing pregnancy if permanent sterilization is an option (see Caution 1 for males).

Products Recommended With Caution or Under Special Circumstances

  1. PZP Vaccine– Has been effectively used in a small number of black bears, although there are currently very limited data on reversibility.
  2. Progestins
    1. May be associated in carnivores with progressive uterine growth that can result in infertility, infections, and sometimes uterine cancer; mammary tissue stimulation also can result in cancer.
    2. For genetically valuable females or for females in which short-term (i.e.,<2 years) contraception is desired, a progestin may be considered on a case-by-case basis.
    3. Should not be used in pregnant animals, since they may suppress uterine contractions necessary for normal parturition. Thus, progestins should only be administered to females CONFIRMED non-pregnant.
    4. If a progestin is used, treatment should only be short term, because of the increased likelihood of side effects with prolonged exposure.
    5. If a progestin is used, treatment should start well BEFORE any signs of proestrus, since the elevated endogenous estrogen can exacerbate side effects of the progestin.
    6. Using progestins in ursids:
      • MGA Implant for 2 years, then remove for pregnancy if possible; non-fertile ovulatory cycles do not substitute for pregnancy in reversing deleterious effects on the uterus; not recommended for more than a total of 4 years (F).
      • Megestrol acetate for seasonal breeders, but for no more than 2 consecutive seasons (F).
      • Depo-Provera® injection (F) - 5mg/kg body wt. every 2 months, no more than 2 consecutive seasons. For ursids, Depo-Provera is the least preferable of the progestins due to the unpredictable duration of efficacy and because it has more side effects.


  1. For carnivore species with induced ovulation (documented for at least some ursid species), vasectomy of males will not prevent potential adverse effects to females from prolonged exposure to endogenous progesterone associated with copulation-induced ovulation resulting in pseudo-pregnancy (although pseudo-pregnancy has not been confirmed in ursids). Castration, which should eliminate copulation, does not result in female pseudo-pregnancies. Endogenous progesterone and progestin contraceptives cause similar side effects.

Research and Monitoring

Continued surveillance for deleterious effects
Contraception Annual Survey
Tissue Submission Form – Pathology
Adverse Reactions Report