1. GnRH Agonists - Gonadotropin Releasing Hormone Agonists are considered the safest reversible contraceptives, but dosages and duration of efficacy are not well established for all species; 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 (see Caution 1 for males).


  1. For species in with induced ovulation (documented for at least some ursid species), Vasectomy of males will not prevent potential adverse effects to females from prolonged, cyclic exposure to endogenous steroids 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 steroids and steroid contraceptives cause similar side effects.
  2. Progestin contraceptives
    a) 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.
    b) Progestins 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.
    c) If a progestin is used, treatment should only be short term, because of the increased likelihood of side effects with prolonged exposure.
    d) 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.
    e) Progestins
    • MGA Implant for 2 years, then remove for 1 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).
    • Depo-Provera® injection (5 mg/kg body wt. every 2 months) (F).
    • Megestrol acetate for seasonal breeders, but for no more than 2 consecutive seasons (F).
  3. PZP vaccine efficacy and safety have been demonstrated in bears

Research and Monitoring

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