National Academy of Sciences Report 1982: Insights on Wild Horses and Burros
In 1982, the National Academy of Sciences (NAS) released a pivotal report on wild horses and burros, commissioned by the Public Rangelands Improvement Act of 1978. This comprehensive study, conducted in collaboration with the Bureau of Land Management (BLM), aimed to assess existing knowledge, evaluate research, and recommend management strategies for these iconic animals.
Population Levels and Census Accuracy
The report highlighted significant discrepancies in population estimates for wild horses and burros. While BLM employees often trusted the accuracy of their censuses, research indicated potential underestimations ranging from 7% in open areas to 60% in more challenging terrains. This uncertainty casts doubt on the reliability of West-wide estimates, suggesting they could be as low as 48% accurate.
Even with consistent census efforts since 1971, the initial figure of 17,000 horses is likely conservative. The use of fixed-wing aircraft in early censuses may have further contributed to underestimation, indicating the actual numbers could be substantially higher.
Annual reports and census data suggested population growth rates of 16-22% per year. However, the Phase I Report identified biases and concluded that actual growth rates were likely 10% or less.
Livestock Competition and Habitat Use
The report addressed the complex issue of livestock competition, emphasizing that decisions on animal carrying capacity are influenced by human values. Biologically, an area might support both cattle and horses, but public opinion could shift the balance in favor of one species over the other.
Horses and cattle often share terrain, though not necessarily at the same time. Their grazing activities can influence vegetation composition, potentially stabilizing ecosystems when balanced. The report noted that light-to-moderate grazing by both species might enhance vegetation productivity, challenging the notion of direct competition.
Despite a 40-year history of livestock competition impacting southwestern subspecies, the report found that wild equids' forage use remains a small fraction compared to domestic animals. The ratio of forage used by livestock to that of feral equids was approximately 23:1, underscoring the minimal impact of wild horses and burros on overall forage consumption.
The 1982 NAS report remains a critical resource for understanding the dynamics of wild horse and burro populations and their interactions with livestock. It provides valuable insights for developing informed management strategies that balance ecological needs with public interests.