Feral horses in the American West pose a complex and expensive management problem. Their populations continue to grow at a rate of 15-20% a year while their range continues to shrink. There is a need to control populations without adversely affecting the genetic diversity of the herd. Current management strategies of removal and adoption are expensive and logistically challenging. An efficacious, long duration, reversible contraception method would provide managers with a tool to economically manage the Virginia Hills Estray horse population. This project evaluates the behavioral effects of the immuno-contraceptive treatments; SpayVac, GnRH, and eCG on mares in the wild setting.
Reduction of free-ranging horses by limiting fertility holds the greatest promise for economic, humane and effective population control. Contraception in feral horses should be safe and potentially reversible, cost effective, efficacious for several years with minimal handling required, and should not affect normal reproductive and harem maintenance behavior.