The Red Desert roundup begins this week, affecting five HMAs. The news release said the current wild horse population in the Complex is approximately 3,000, compared to a total AML of 724.
If each HMA is at 4X AML, the need for this and other management actions, such as fertility control, is obvious.
The operation was originally authorized in 2016 but the supporting documents were revised in 2017. Data in the Final EA are not sufficient for a report on the entire Complex but do allow reports for a few of the HMAs.
The Stewart Creek HMA covers 168,000 acres and has an AML of 175. The horses allowed by plan require 2,100 AUMs per year and the stocking rate is approximately one wild horse per thousand acres, in line with the average rate across all HMAs.
The HMA intersects one allotment, shown in white on the following map. The EA states on page 54 (page 58 in the pdf) that the allotment boundary is similar to the HMA boundary except the allotment includes about 5,000 acres outside the HMA. Thus, the estimated size of the allotment is 173,000 acres.
Table 5 in the EA provides the grazing season and authorized forage. Livestock calculations are based on cow/calf pairs for a direct comparison to wild horses. The resource requirements of wild horses and cow/calf pairs are said to be equivalent.
The portion of the allotment inside the HMA is 168,000 ÷ 173,000 = .971.
The estimated forage available to livestock inside the HMA is 8,138 AUMs per year, assuming the resource is evenly distributed across the parcel (97.1% of 8,380).
The Stewart Creek permittees would have to place 1,292 cow/calf pairs inside the HMA to graze off 8,138 AUMs in 6.3 months. The stocking rate would be 7.7 cow/calf pairs per thousand acres.
These management indicators are compared in the following charts.
The HMA is managed primarily for livestock, with the horses receiving 21% of the total authorized forage (excluding wildlife).
If the HMA is at 4X AML, the pre-gather population of 700 would include 525 excess horses and the area would be classified as ‘overpopulated.’.
However, the forage assigned to livestock would support an additional 678 wild horses, for a true AML of 853. There are no excess horses in the HMA, there is no need for a roundup and there is no justification for a fertility control program.
RELATED: Red Desert Horses Get Short End of Stick?, Rationale for AMLs?
Western Horse Watchers Association 
Every time a counter argument for a roundup comes it starts with: there is not as many horses as is Estimated, than the second argument is use birth control. Contradictory and immediately gives them reason not to question a population over. Stop using a tool as an argument, it only validates their faulty presumption of overpop. so they do not have to prove themselves. Plus. Birth control along with the low low aml is and has been shown to be detrimental if anyone really wants to understand herd wisdom and dynamics. – – In this herd area are Uranium mines, 1000’s of permitted cattle And permitted wells. The back roads where the horses are have become high speed truck lanes. We the people gave the state of WY One billion $ in 2014/15 from our receipts to add roads for the above. etc. No more mentioning pzp etc. First and foremost challenge the AML and Estimates.
Practically the entire Stewart Creek HMA will be part of BLM 2021 Fourth Quarter Gas and Oil Lease Sale program. https://eplanning.blm.gov/public_projects/2003636/200393912/20029519/250035720/March%202021%20Wyoming%20Oil%20and%20Gas%20Lease%20Sale%20EA_draft.pdf