Rangeland and Herd Management

Horses nuzzling in a field

Healthy Horses on Healthy Ranges

In 1971, wild horses and burros were found roaming across 53.8 million acres of Herd Areas, of which 42.4 million acres were under the BLM's jurisdiction. Today the BLM manages wild horses and burros in subsets of these Herd Areas (known as Herd Management Areas) that comprise 31.6 million acres, of which 26.9 million acres are under BLM management.

To manage wild horses and burros on public lands, the BLM uses qualified science and technology staff and a citizen-based advisory board. The agency also supports research to keep track of the health of wild horses and burros and the condition of the range. This includes research on population growth-supression techniques.

The BLM’s goal is to ensure and maintain healthy wild horse populations on healthy public lands. To do this, the BLM works to achieve what is known as the Appropriate Management Level (AML) – the point at which wild horse and burro herd populations are consistent with the land’s capacity to support them. In the context of its multiple-use mission, AML is the level at which wild horses and burros can thrive in balance with other public land uses and resources, including vegetation and wildlife. 

The AML is a range of low to maximum levels that allows for population growth over a four- to five-year period.  To establish AML, the BLM evaluates several years of rangeland resource and population data.  Those evaluations look at information relating to vegetation, soils, weather, and water quality.

Each Herd Management Area (HMA) has its own AML. When AML is exceeded, the excess animals are to be removed and then prepared for adoption or sent to off-range pastures.

This type of rangeland management is different from management of wildlife, which are controlled by hunters and natural predators, or livestock, which are controlled by grazing permits. To learn more about BLM's grazing program, click here. Because of Federal protection and a lack of natural predators, wild horse and burro herds can double in size about every four years. 


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