How Many Wild Horses Can the Four Mile HMA Support?

A new resource enforcement project for the Bible Springs Complex has been created but no documents have been posted and public involvement has not been requested.

The Complex includes the Tilly Creek, Bible Spring and Four Mile HMAs.

The preliminary environmental assessment is still months away so let’s use other data sources, such as the Western Watersheds map and RAS to bootstrap the answer.

  • Identify allotments that overlap the HMA
  • Determine average forage production on those allotments
  • Convert to wild horses
  • Calculate the True AML

The HMA covers 61,273 acres and the 60 horses currently allowed by plan require 60 × 12 = 720 AUMs per year.  The stocking rate allowed by plan is about one wild horse per thousand acres, in line with the target rate across all HMAs (27,000 animals on 27 million acres).

The land must produce 720 ÷ 61,273 × 1,000 = 11.8 AUMs per year per thousand acres to support the horses.

Can it produce more?

The HMA intersects six grazing allotments according to the map.  (Click on image to open in new tab.)

Four Mile HMA Allotments 03-20-22

The Allotment Master Report provides acreage, management status and active AUMs.

Four Mile Allotment Calcs 03-20-22

Three of the allotments are in the Improve category along with 56.1% of the public acres.

The average forage production for livestock across the six allotments, the total AUMs divided by the total acres times 1,000, is 44.7 AUMs per year per thousand acres, almost four times higher than the amount needed for the horses.

The total forage production in the HMA is 11.8 + 44.7 = 56.5 AUMs per year per thousand acres, which would support 56.5 ÷ 12 = 4.7 wild horses per thousand acres.

The HMA contains 61,000 acres so the True AML should be around 4.7 × 61 = 286.

The number of horses displaced from the HMA by permitted grazing is 286 – 60 = 226.

The True AML can be achieved by confining the ranchers to their base properties and letting them pay market rates to feed their animals.

What do you think happens during the off season?

RELATED: New Resource Enforcement Plan for Bible Springs Complex?

One thought on “How Many Wild Horses Can the Four Mile HMA Support?

  1. According to new PEER data, of 178,103 acres in the complex:
    Standards met: 6,312
    Standards not met due to livestock: 171,776
    Not assessed: 14 acres

    But advocates don’t talk about that, they just ask for more PZP.

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