Last month, the Bureau of Land Management (BLM) completed a wild horse roundup in Nevada. Using helicopters, BLM officials gathered 113 horses from the Reveille Herd Management Area (RHMA), relocating 74 and re-releasing 39 of the horses back to the RHMA after treating the 22 mares with fertility control vaccine PZP-22, the Pahrump Valley Times reports.

The purpose of the roundup was to “reduce the impact to rangeland health and wildlife habitat by removing excess horses,” according to a BLM release. Mares were injected with PZP-22 to “slow population growth rates” since the vaccine prevents pregnancy for one to two years. Both actions are to keep populations under control per the court-mandated Appropriate Management Level (AML), which is 138 horses. Following this recent roundup, the current wild horse population is between 100 and 125 animals. Another gather will be scheduled once the AML is met, according to the Pahrump Valley Times.

Horses that were relocated to the BLM’s Indian Lakes Off-Range Wild Horse and Burro Corrals will be “readied” for future adoption. Horses not adopted or sold will be moved to long-term holding pastures and cared for under the 1971 Wild Free-Roaming Horses and Burros Act.