2021 Foaling Season Will Determine PZP Effectiveness in Northern Nevada

By Amelia Perrin

(March 24, 2021) As the American Wild Horse Campaign (AWHC)’s fertility control program gallops toward the second year of success, many are wondering what this spring's foaling season will look like. Don’t worry, you’ll still get all your cute baby horse pictures, just fewer babies! 

Photo by Christine Dallas Photography

The free-roaming horses of Northern Nevada’s Virginia Range are at the mercy of rapid commercial and residential development that is rapidly encroaching on their habitat, reducing the size of the land available to sustain them. So to avoid overpopulation and the removal of these state-managed horses, AWHC implements a birth control program for wild horses using the PZP immunocontraceptive vaccine.  Our project, which inoculates mares via remote darting, is now the largest fertility control program for wild horses in the world 

Photo by Marc Crumpler

When the program restarted in 2019, we began darting in the middle of foaling season, and many of the mares were already pregnant. As a result, many foals were born in Spring and Summer 2020. Our field team is about 23 months into the program and over 1,300 wild mares have been treated with PZP fertility control. That means this foaling season will be one to watch because not only will it show unequivocally that PZP works, but it will also firmly set in stone that our program is a model that is applicable to other wild horse herds across the West. 

Members of the darting team

Since PZP is not 100 percent effective (it comes in close at 97%!) and because we have not darted every single mare on the range, foals are still expected - just far fewer of them! That means photographers will still be out on the range snapping all the adorable photos they can of the 2021 foals…. So stay tuned for some serious doses of cuteness coming your way soon!

Learn more about our program here.