a thriving natural ecological balance on the public lands,” protect wildlife habitat, and prevent range deterioration.

The goal of protecting free-ranging horses and burros while managing and controlling them to achieve a vaguely defined thriving natural ecological balance within the multiple-use mandate for public lands has challenged BLM’s Wild Horse and Burro Program since its inception. Amendments to the Wild Free-Roaming Horses and Burros Act have not diminished the difficulty. BLM is to monitor the population size to determine where there is an excess of horses and burros; such a situation is to be identified when “a thriving natural ecological balance and multiple-use relationship” is threatened (P.L. 92-195 as amended by the Public Rangelands Improvement Act of 1978, P.L. 95-514). It is BLM’s responsibility to determine when that relationship is under threat and to remove animals to achieve balance. The legislation allows the destruction of old, sick, or lame animals. Excess animals removed from the range may be adopted. Those for which there is no adoption demand are to be “destroyed in the most humane and cost efficient manner possible”; however, the destruction of healthy, unadopted free-ranging horses and burros has been restricted either by a moratorium instituted by the director of BLM or by the annual congressional appropriations bill for the Department of the Interior in most years. Free-ranging horses and burros have successfully sustained populations in North America for over 300 years, and no large predator widely overlaps with their territory. Since 1989, adoptions have seldom exceeded the number of animals removed from the range; in the 2000s, the discrepancy neared a 2:1 ratio of animals removed to animals adopted (GAO, 2008). Thus, BLM’s effort to control horse and burro numbers by removing animals from the range has led to the stockpiling of “excess” horses and burros in holding facilities (Figures 1-1 and 1-2). In fiscal year 2012, more than 45,000 animals were in holding facilities, and their maintenance consumed almost 60 percent of the Wild Horse and Burro Program’s budget (BLM, 2012a).

With holding costs in 2010 projected to nearly double those in 2004 (Bolstad, 2011), the U.S. Senate Committee on Appropriations in 2009 instructed BLM to “prepare and publish a new comprehensive long-term plan and policy for management of wild horses and burros” (U.S. Congress, Senate, 2009). BLM responded with a proposed strategy designed around seven topics. With respect to science and research, one method for improving the use of science in its management of horses and burros was to “commission the [National Academy of Sciences] to review earlier reports and make recommendations on how the BLM should proceed in light of the latest scientific research” (BLM, 2011a).


The committee formed by the National Research Council of the National Academy of Sciences in response to BLM’s request was given a long statement of task that required a variety of expertise (Box 1-1). The charge called on the Committee to Review the Bureau of Land Management Wild Horse and Burro Management Program to investigate the annual rates of growth in the animal populations, the implications of genetic diversity for their long-term health, and how they interact with the environment. It also asked the committee to assess the effects of management actions, such as treating animals with contraceptives or removing animals from the range, and to evaluate BLM’s tools for measuring the effects. Agency methods for determining the number of animals living on the range and the number of animals appropriate for the range were also to be examined. Finally, the committee was tasked to identify options that could address stakeholder concerns making use of the best available science.

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement