The Campaign Against America’s Wild Horses, a leader in nonsurgical sterilization, reported today that 165 mares received 165 doses of PZP during the month, 31 given as a primer and 134 as a booster.
Over the life of the program, which began in 2019, the advocates have pumped 8,927 doses of the pesticide into 2,007 mares.
Eleven foals have been born year-to-date. One died of unspecified causes.
The current population is thought to be 3,480 with 353 horses listed as missing, compared to 3,444 with 338 horses listed as missing in February.
The population was 3,465 with 342 horses listed as missing in January and 3,471 with 336 listed as missing in December.
The goal for April: “Continue to maximize booster treatments to mares across the Virginia Range as we move through spring breeding season to prevent pregnancies, and continuing to allow for humane population decrease.”

Not discussed in the report:
- Long-term population goal
- Number of viable mares
- Size of breeding population
- Loss of genetic diversity
- Changes in death rate and sex ratio
- Unlawful use of pesticides
PZP tricks the immune system into attacking the ovaries, resulting in sterility after five years of treatment.
The report will be submitted to the Nevada Department of Agriculture.
RELATED: Virginia Range Darting Update for February 2024.
