Contraception of Wild and Feral Equids

Fertility control in wild horses has been contraceptive effects for a second year, and the vaccine's attempted with both stallions and mares. Nonreversible effects are reversible after short-term use. surgical sterilization by means of vasectomy has been After 6 years of treating 52 different mares with successful in inhibiting reproduction in wild horses in porcine zonae pellucidae, contraceptive efficacy exceeded Montana and Nevada. Administration of a microencapsulated 95 percent. In more recent studies, investigators are studying form of testosterone to wild stallions reduced sperm counts the effects of long-term treatment (4 to 7 consecutive years) and motilitv and foal counts. In a third ap~roach. lntra~eriupon ovarian function. The orc cine zona Dellucida 1PZPI ronea S asttclM rnp ants conla n ng eln.ny esolrao o an0 vacc ne nas a so probe0 lo oe effect ve n contracepr ng ~roaesterone b ocneo ov, a1 on n w o mares lor , D lo 3 free roam na fera oonnevs in Vtra n s anos hat onal Par. years The first immunological fertility control of free-ranging wildlife was accomplished with wild horses, Initial experiments demonstrated that immunization with porcine zonae pellucidae was capable of causing contraception in domestic mares. Later, contraception was achieved with the vaccine in free-ranging horses. That study demonstrated that the vaccine (1) could be delivered remotely via darts, (2) was safe to administer to pregnant animals, and (3) did not alter social behavior. A followup study revealed that a single annual booster inoculation would extend the