Case studies in wildlife immunocontraception: wild and feral equids and white-tailed deer.

The research discusses the successful use of porcine zona pellucida (PZP) immunocontraception as a non-lethal control method for managing the population growth of wild horses and deer.

Objective and Methods

• The study aimed to investigate non-lethal methods for wild equines and deer management, particularly in situations where lethal controls aren’t allowed or safe.
• The researchers employed the use of single or multiple doses of Porcine Zona Pellucida (PZP) vaccination, delivered to the wild horses and deer via darts.
• They looked at the contraceptive efficacy of the vaccine in both animals, assessing potency after single or multiple inoculations. They also monitored behavioral changes, the contraceptive effects’ reversibility, and physiological changes in the animals.

Findings

• In horses, the contraceptive efficacy after administering two doses of PZP ranged from 90% to 100%, and after a single dose, from 19% to 28%.
• Controlled-release form of the PZP vaccine resulted in pregnancy rates of 7% to 20% in mares.
• No discernible alterations in the social organization or behaviors among the treated horses were detected.
• The contraceptive effects were reversible after four consecutive years of treatment. However, after 5-7 years of treatment, mares exhibited signs of ovulation failure and decreased urinary estrogen concentrations were noted.
• For deer, two PZP shots were 70-100% effective in preventing fawn births for the first year and one shot was less or equal to 20% effective, with late-season pregnancies. A single annual booster shot decreased fertility to 20% for the following year.
• Extended breeding seasons due to the contraceptive treatment led to less energy consumption compared to that caused by pregnancy. After two years of treatment, the ovaries of the deer remained normal.

Conclusion

• These research findings suggest that the use of PZP immunocontraception can be successfully used to manage the population of certain free-roaming groups of wild horses and deer. It not only offers a non-lethal solution to control wildlife population but also appears to have minimal impact on animal behavior and health over time.