Subscribe for 17¢ / day
Wild stallions

The BLM is proposing to alter its fertility control program of wild horses in the Pryor Mountains.

Although the birthrate for the Pryor Mountain wild-horse herd has been cut in half under a current fertility control program, the Bureau of Land Management is proposing to modify the plan to cut the birthrate even further.

The BLM’s Billings Field Office has released an environmental assessment for public comment that would modify the existing fertility control on the Pryor Mountain Wild Horse Range to meet its management goals. The range is located about 60 miles south of Billings.

According to the EA, the current protocol treats mares ages 2, 3, 4, 11 and older. Yet numerous treated mares ages 2, 3 and 4 have foaled; most likely due to timing of treatments as a result of inaccessibility to the area in the spring. The 2-year-olds that foal are becoming pregnant as 1-year-olds.

The EA also said that the 5- to 10-year-old cohort that hasn’t been vaccinated is “too large a group” to stabilize herd growth.

Using the vaccinations, BLM has cut the wild horses’ population growth from 17.5 percent to 8 percent. Foal survival rates have been as high as 88 percent. As a result, the population continues to exceed the capacity of the range, even with a bait trap gather in 2012, the BLM contended.

To address its concerns, the BLM is proposing to treat 1-year-old mares in the fall and continue to treat mares ages 2, 3 and 4 years old. Mares ages 5 to 9 would not be treated, but 10-year-olds and older mares would be vaccinated until they are 20. Mares 21 and older would no longer be treated.

The Billings Field Office is accepting public comment on its proposal for 30 days. The EA is available for review by visiting the field office website at

Fertility control has been utilized on the wild-horse range since 2001. The current fertility control program began in 2011 and expires this year.

The EA also analyzes two other alternatives: continuing with its current program or halting fertility control all together.

Comments can be emailed to: by Feb. 18. Written comments may be mailed or hand delivered to James M. Sparks, Billings Field Office, 5001 Southgate Drive, Billings, MT 59101.

After comments are analyzed and incorporated into the EA, the BLM will issue a final decision.