November 4, 2010 – Fertility Control Preliminary EA

The Billings Field Office has released its preliminary Environmental Assessment (EA) and an unsigned Finding of No Significant Impact (FONSI) for a fertility control program. The Dear Reader letter reads as follows:

November 1, 2010

Dear Interested Party:

Enclosed for your review and comment is the Pryor Mountain Wild Horse Range (PMWHR) Fertility Control Tiered Preliminary Environmental Assessment (EA) DOI-BLM-MT-010-2011-0004 and unsigned Finding of No Significant Impact (FONSI) for the implementation of a fertility control program on the PMWHR. The documents will be available for 30-day public review and comment beginning November 1, 2010.

This EA is tiered to the PMWHR/Territory EA (MT-010-08-24) and Herd Management Area Plan (HMAP) May 2009. This tiered EA has been prepared to analyze the impacts associated to wild horses from application of fertility control within the PMWHR through 2015. The analysis from the HMAP is incorporated by reference. All other impacts and affected environment are already described and analyzed in the HMAP and subsequent FONSI and Decision Record (DR). These documents are available on the Bureau of Land Management (BLM), Billings Field Office (BiFO) website at

The BLM proposes to apply fertility control to selected mares on the PMWHR through 2015 in order to help maintain the appopriate management level of 90-120 wild horses. The BLM has determined through the EA and HMAP May 2009 and subsequent FONSI and DR that 90-120 wild horses (excluding current year’s foals) are needed in order to ensure and achieve a thriving natural ecological balance. The fertility control would begin in 2011 and continue through 2015. The proposed action should help prevent deterioration of the rangelands and help maintain a thriving natural ecological balance and multiple-use relationships as described in the HMAP. The method of fertility control would be through remote darting application utilizing liquid Porca Zona Pellucide (PZP) into selected mares over 1 year of age.

Comments on the EA or the unsigned FONSI must be received at the letterhead address by close of business on December 1, 2010. Only written comments will be accepted either through standard delivery, fax or hand delivered. The BLM will consider any comments and revise the EA or FONSI as appropriate.

Thank you for your interest in the management of the PMWHR by the Billings Field Office. If you have questions, please contact Jared Bybee, Wild Horse and Burro Specialist, at (406) 896-5223.



James M. Sparks

Field Manager

These documents can be found by clicking here or on the cover page image below. Remember, comments are due on December 1, 2010.

For more information on PZP, please click here to read the current version of the PZP Q&A. This is a very helpful document that was put together by some of the experts in the field and is based on actual research.

Published in: on November 4, 2010 at 10:27 am  Comments (3)  

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3 CommentsLeave a comment

  1. Hi Matt,
    This is certainly interesting information in the Q&A’s. It sounds good if the mares don’t continuously come into heat, which it sounds like they don’t, then the herd will not be out of sync.
    We do want the numbers to stay under control, so the horses are healthy with plenty of feed and not over grazing their range, coming out of winter well,etc.

    Thank you.

  2. HiMatt,

    I get e-mails from the Cloud Foundation and they made a few comments that has me wondering. If the BLM uses PZP on mares 1-5 yo what percentage of the herd is that? It sounds good on paper but what about in reality?

    • Hello,
      Thanks for your comment. The BLM’s proposed action is to treat females at ages 2, 3, and 5 and over age 10. I’ll have to get back to you with the specifics on numbers as I am away from the office right now. Also, it should be noted that I did not treat any mares in September in 2010. I didn’t treat any in August or July either. The treatments happened in March, April, May, and June, with most of them occurring earlier on. In something like this, it is very important to know the origins and validity of statements.

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