The AML for the Pryor Mountain HMA did not increase in the updated management plan but the interval between high and low decreased, suggesting the birth rate will be going down and the death rate will be going up (as the age of the herd increases).
The range between the endpoints is usually based on a doubling of herd size every four to five years, which might make sense in areas where nature is allowed to run its course.
For example, at the Fifteenmile HMA in Wyoming, the AML is 100 to 230.
What about HMAs where the advocates are involved?
At Stewart Creek, where WYWHIP poisons the mares with PZP, the range is 125 to 175.
The closer the endpoints the lower the growth rate.
The previous AML at Pryor, 90 to 120, yields a growth rate of roughly 5.9% per year for five years.
The new AML, 107 to 120, yields a growth rate of 2.3% per year over the same period.
You can determine the growth rate by solving this relationship for GR, where AMLH is upper endpoint, AMLL is the lower endpoint, GR is the growth rate in percent and n is the period in years.
Or you can use this spreadsheet.
You can check the calculation by plugging the results into the formula.
How will the new AML be achieved?
Long-term use of PZP, much to the delight of the advocates, with the inevitable result of permanent infertility and herd collapse.
HOMEWORK: What are the expected growth rates at Fifteenmile and Stewart Creek?
EXTRA CREDIT: Stop giving the advocates money.
PREVIOUS: Foal-Free Friday, Casting a Wider Net Edition.
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