CASE-STUDIES IN WILDLIFE IMMUNOCONTRACEPTION - WILD AND FERAL EQUIDS AND WHITE-TAILED DEER

Non-lethal management methods are required for wild equids that are pr otected by law and for deer inhabiting areas where lethal controls are not legal or safe. Single or multiple inoculations of porcine zona pe llucida (PZP) vaccine have been delivered to wild horses and deer by m eans of darts. Contraceptive efficacy in horses after two inoculations ranged from 90% to 100%, and after a single inoculation ranged from 1 9% to 28%. Mares given a controlled-release form of the vaccine had fo aling rates ranging from 7% to 20%. No detectable changes in social or ganization or behaviours among treated horses occurred. Contraceptive effects were reversible after 4 consecutive years of treatment but 5-7 years of treatment resulted in ovulation failure and decreased urinar y oestrogen concentrations. Among deer, two inoculations were 70-100% effective in preventing fawns, but one inoculation yielded a contracep tive efficacy of less than or equal to 20%, with pregnancies occurring late in the breeding season; a single annual booster inoculation redu ced fertility to 20% in the second year. Energy costs of extended bree ding seasons were less than those resulting from pregnancy. After two years of treatment, ovaries appeared normal. These studies suggest tha t PZP immunocontraception can be successfully applied to certain free- roaming populations of wild horses and deer.