Statement of Task
At the request of the Bureau of Land Management (BLM), the National Research Council (NRC) will conduct an independent, technical evaluation of the science, methodology, and technical decision-making approaches of the Wild Horse and Burro Management Program. In evaluating the program, the study will build on findings of three prior reports prepared by the NRC in 1980, 1982, and 1991 and summarize additional, relevant research completed since the three earlier reports were prepared. Relying on information about the program provided by BLM and on field data collected by BLM and others, the analysis will address the following key scientific challenges and questions:
- Estimates of the wild horse and burro populations: Given available information and methods, how accurately can wild horse and burro populations on BLM land designated for wild horse and burro use be estimated? What are the most accurate methods to estimate wild horse and burro herd numbers and what is the margin of error in those methods? Are there better techniques than BLM currently uses to estimate population numbers? For example, could genetics or remote sensing using unmanned aircraft be used to estimate wild horse and burro population size and distribution?
- Population modeling: Evaluate the strengths and limitations of models for predicting impacts on wild horse populations given various stochastic factors and management alternatives. What types of decisions are most appropriately supported using the WinEquus model? Are there additional models BLM should consider for future uses?
- Genetic diversity in wild horse and burro herds: What does information available on wild horse and burro herds’ genetic diversity indicate about long-term herd health, from a biological and genetic perspective? Is there an optimal level of genetic diversity within a herd to manage for? What management actions can be undertaken to achieve an optimal level of genetic diversity if it is too low?
- Annual rates of wild horse and burro population growth: Evaluate estimates of the annual rates of increase in wild horse and burro herds, including factors affecting the accuracy of and uncertainty related to the estimates. Is there compensatory reproduction as a result of population-size control (e.g., fertility control or removal from herd management areas)? Would wild horse and burro populations self-limit if they were not controlled, and if so, what indicators (rangeland condition, animal condition, health, etc.) would be present at the point of self-limitation?
To accomplish the committee’s comprehensive charge, members were appointed on the basis of their scientific research and experience with the questions involved in the statement of task. Experts were selected from the fields of behavioral ecology, conservation biology, genetics, natural-resources management and range ecology, population ecology, reproductive physiology, sociology, veterinary medicine, and wildlife ecology. (The committee members’ biographies are in Appendix A.) The committee also retained a consultant who had expertise in equine reproduction.
The committee’s study was the first examination of BLM’s Wild Horse and Burro Program by the National Research Council in over 20 years. The National Research Council had published three reports on free-ranging horses and burros under BLM’s jurisdiction. The first two reports, Wild and Free-Roaming Horses and Burros: Current Knowledge and Recommended Research, Phase I Final Report (1980) and Wild and Free-Roaming Horses and Burros: Final Report (1982), completed the first and third phases of a three-phase study mandated