National Academy of Sciences Report 1982: Insights on Wild Horses and Burros
The 1982 National Academy of Sciences (NAS) report provides a comprehensive analysis of wild horses and burros on public lands, commissioned by the Public Rangelands Improvement Act of 1978. This report, developed in collaboration with the Bureau of Land Management (BLM), outlines critical findings on population estimates, livestock competition, and management strategies for these iconic animals.
Population Levels and Census Accuracy
The report highlights significant discrepancies in population estimates for wild horses and burros. While BLM employees often trust the accuracy of their censuses, research indicates that these counts may miss between 7% and 60% of animals, depending on the terrain. This uncertainty raises questions about the reliability of West-wide estimates, cautioning against using blanket correction factors to adjust census figures.
Historical census methods, such as those used in 1971, likely underestimated populations due to reliance on fixed-wing aircraft and other limitations. Consequently, the reported figure of 17,000 wild horses is suspected to be conservatively low.
Despite claims of annual population increases between 16% and 22%, the report suggests that actual growth rates are closer to 10% or less, considering biases in census data and variations in reproduction and survival rates.
Livestock Competition and Habitat Use
The report examines the complex dynamics between wild horses, burros, and livestock. It notes that the decision to prioritize one species over another often reflects human values rather than ecological necessity. While horses and cattle share habitats, their grazing patterns can complement each other, potentially enhancing vegetation productivity.
However, the report acknowledges that livestock competition has historically contributed to the decline of certain subspecies in the southwestern United States. It emphasizes the need for balanced management to ensure sustainable forage use and ecosystem health.
Findings on forage consumption support the practice of assigning an animal unit equivalent of 1.25 to mature horses. Despite concerns about competition, wild equids account for a small fraction of total forage use compared to domestic livestock, with a ratio of approximately 23:1.
Overall, the 1982 NAS report underscores the importance of accurate population assessments and thoughtful management strategies to preserve the ecological balance and well-being of wild horses and burros on public lands.