BILLINGS, Mont. – The Bureau of Land Management (BLM) Billings Field Office released a decision today that will allow for the continued use of fertility control on the Pryor Mountain Wild Horse Range (PMWHR). The Decision Record, Finding of No Significant Impact (FONSI) and the Environmental Assessment on which this decision is based can be found on the Billings Field Office website at

Fertility control has been used on the PMWHR in varying intensities and management applications since 2001. The current fertility control protocol using ZonaStat-H, also known as liquid PZP, began in 2011 and will expire after this season’s remote darting is complete. Currently 70-80 percent of the mares are treated annually. 


“We had a lot of constructive feedback and information provided to us from the public and some very productive discussions with individuals and groups like the Pryor Mountain Wild Mustang Center and The Cloud Foundation,” said Billings Field Manager Jim Sparks. “The Billings Field Office is excited to be on the cusp of nearly eliminating the need for wild horse removals due to the use of PZP.”


The proposed action adopted by the Decision Record was developed based on results from the 2011-2015 fertility control protocol and past use of the PZP vaccine which has been effective in managing the herd numbers. It is composed of a specific treatment prescription, including treating mares ages 2-4 and 10-20 years old, along with thresholds allowing for adaptive management.


If you have questions, please contact Jared Bybee at the Billings Field Office at (406) 896-5223.



Source:  BLM-Montana/Dakotas



Onaqui HMA 02/27/12 by BLMUtah, on Flickr
Creative Commons Creative Commons Attribution 2.0 Generic License   by  BLMUtah 

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