Today, there are 9,363 fewer wild horses and burros on lands managed by the Bureau of Land Management than the bureau estimated in 2023.
The annual wild horse and burro population estimate showed a marked increase in wild horses on public lands for the third year since 2020. In total, the BLM still estimates that there are approximately 73,520 federally protected wild horses and burros on the rangelands. Due to the realities of aerial and statistical analyses, the population estimate accounts for a range of uncertainty between 63,432 animals and 85,249 animals.
Though this latest estimate represents the largest one-year reduction in overpopulation since 1985, the estimated population remains nearly three times what scientists estimate public lands can sustainably support.
Meanwhile, a 2021 study published in the Journal of Wildlife Management suggests that some 300,000 wild horses are likely spread across different lands throughout the West.
“Protecting and managing wild horses and burros on public lands is a responsibility that the BLM takes extremely seriously,” said BLM Director Tracy Stone-Manning. “By addressing overpopulation, we are not only ensuring the long-term well-being of wild horses and burros but also safeguarding the delicate balance of our ecosystems for the benefit of all wildlife and the health of our public lands.”
Though the exact causes of the population reduction cannot be definitively determined, the BLM has taken steps in recent years to address overpopulation. For example, since the March 2023 estimates were released, the BLM removed 11,784 animals from overpopulated herds and offered them for adoption to qualified homes.
Since then, BLM has placed 7,887 animals into private care through adoptions, sales, and transfers. Between 2020 and 2023, the BLM removed about 50,000 wild horses and burros. This compares to about 27,000 animals that were removed in the prior four years, 2016-2019.
The BLM has also worked to increase the use of fertility control vaccines, which could be contributing to slower growth for some herds. From 2020 to 2023, about 4,237 treatments were conducted, compared to 2,606 treatments conducted from 2016 to 2019.
Fertility control has remained the primary control method advocated for by the Humane Society of the United States. Over the years, numerous organizations have accused HSUS of owning and profiting off of the patent on porcine zona pellicula (branded as ZonaStat-H), the contraceptive used on wild horse populations. Meanwhile, HSUS asserts that the HSUS and the Humane Society Legislative Fund do not benefit from the sale and distribution of PZP.
In addition, most of the Western U.S. experienced a severe 2022-2023 winter with deep snow, which impacted wildlife populations and may have increased mortality in some wild horse herds or caused animals to disperse to other areas unknown to surveyors.
The BLM plans to continue efforts to bring wild horse and burro populations back to a healthy level. The agency recently released its plan to gather and remove approximately 20,000 wild horses and burros and treat 1,400 horses with fertility control in Fiscal Year 2024, with the goal of placing 10,000 animals into private care through adoptions and sales.
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