On the basis of its assessment of the issues contained in the statement of task, the committee concluded that tools available to the Bureau of Land Management (BLM) could help the agency to address formidable challenges facing the Wild Horse and Burro Program successfully. Using those tools would require changes in common practices, and new approaches would probably be more expensive than standard procedures in the short term. Over the long term, however, improvements may be cost-effective and help to improve the public’s confidence in BLM with respect to the management of free-ranging horses and burros in the context of the agency’s multiple-use mandate for public lands.
In its presentation to the committee (Bolstad, 2011), BLM highlighted two goals developed in response to the U.S. Senate Committee on Appropriations’ 2009 demand for a comprehensive, long-term plan for the Wild Horse and Burro Program: to balance removals with adoptions and to achieve appropriate management levels (AMLs). The committee found that it may be possible to meet those program goals but not with the system in place at the time of the committee’s study.
Chapters 1 and 6 stated that the program reportedly spent almost 60 percent of its fiscal year 2012 budget, or over $40 million, caring for more than 45,000 animals that had been removed from the range (BLM, 2012). Over 30,000 of those animals, almost all horses, were in long-term holding. From 2002 to 2011, the number of horses removed from the range each year averaged over 8,000; roughly half those removed were ultimately placed in long-term holding. The continued removal of horses perpetuates a supply of animals that outstrips adoptions each year. The Government Accountability Office (GAO, 2008) concluded that holding-facility costs would “continue to overwhelm the program” if adjustments were not made; the committee concurs with this assessment. “Business as usual” practices will probably also continue to alienate interested parties concerned about the free-ranging nature of the animals and the program’s fiscal sustainability.
Furthermore, as discussed in Chapters 2 and 3, the management strategy of removing free-ranging horses and burros from the range leaves the animals that remain on the range unaffected by density-dependent population processes. Thus, population growth is not regulated by self-limiting pressures, such as lack of water or forage, and this allows horse, and possibly burro, populations to grow at an annual rate of 15-20 percent. Such successful herd productivity hampers BLM’s ability to keep population sizes within AMLs and affects the agency’s ability to maintain rangeland health.
Fortunately, tools that could help BLM to tackle many of those challenges already exist. Available improvements of common management practices on the range have been reviewed in this report and, if broadly and completely implemented, could address concerns about animal welfare and program expense. More immediately, they could help BLM to respond to two chief criticisms of the Wild Horse and Burro Program: unsubstantiated estimates for Herd Management Area (HMA) populations and of the population as a whole and lack of evidence that management decisions are informed by science. Addressing those issues could help increase public confidence in the agency.
Improving Population Estimates and Informing Management Actions with Science
Consistently conducted surveys of horse and burro populations that use scientifically sound methods of population estimation would substantially increase the credibility of the numbers reported by the Wild Horse and Burro Program. Improving the methods of horse and burro surveys was also called for by the National Research Council Committee on Wild and Free-Roaming Horses and Burros in its 1980 and 1982 reports. BLM has already taken a step in that direction through its collaboration with the U.S. Geological Survey (USGS). This cooperative work has demonstrated that survey methods available to BLM can increase the accuracy and quantify the uncertainty of population estimates.
Statistically rigorous and scientifically defensible estimates of demographic parameters and population sizes of horses and burros constitute essential data for any model that could project the outcome of different management decisions. As reviewed in Chapters 3 and 6, the absence of such data limits the applicability of modeled outcomes projected by WinEquus because the input parameters used in the model are most likely based on default datasets available within WinEquus rather than on the specific population being modeled. It is unknown whether the default datasets are representative of other horse herds or even of the populations studied, given that the default parameters were estimated from data collected more than 2 decades ago. There are no representative population data on burros. Inaccurate data on demographic and management parameters and population size and structure undermine the relevance of modeling effects of management decisions. Similarly, it undercuts efforts to develop forage production estimates made using forage utilization data as recommended in the Wild Horses and Burros Management Handbook.
In addition to more accurate demographic and population-size data, the Wild Horse and Burro Program would benefit from a more comprehensive model or suite of models. WinEquus can capture effects of contracepting mares, changing the sex ratio, or removing animals from the range, but it cannot model the implications of contracepting males, forecast the effects of management decisions on genetic diversity, or link the effect of climatic variability on forage availability with survival and reproductive success. It also lacks
sensitivity-analysis and economic-optimization capabilities, both of which could help managers of equid populations to set priorities for management actions.
A model that captures the population-level effects of contracepting males and females could help in designing efficacious, herd-specific contraceptive treatment plans to meet management goals. According to BLM’s presentation to the committee, the agency treated an average of 500 mares a year with the porcine zona pellucida (PZP) vaccine from 2004 to 2010; just over 1,000 were treated in 2011 (Bolstad, 2011). Contracepting 500-1,000 mares a year with a 2-year vaccine will not substantially lower the rate of growth of a population of over 30,000 horses. To reduce the population growth rate with contraception, a much higher proportion of the population would need to be treated in a comprehensive, strategic fashion, making use of PZP (in the PZP-22 or SpayVac® formulation) and GonaCon™ for females and chemical vasectomy for males. Recording information on the date and type of treatment applied would allow BLM to measure the success of its contraception management actions and adapt its strategy accordingly. It would also contribute to knowledge about the effects of contraception on individual reproductive success if the contraceptive is administered multiple times, on the longevity of treated mares, and on behavior in individuals, harems, or the larger population. Tracking responses to a large-scale fertility-control strategy would be particularly important for BLM to be able to respond quickly and appropriately to known and unknown side effects that may affect population or genetic health. Any information learned from analysis of management actions could be used to modify the model or models to continually improve their predictive ability and hence their utility going forward.
Another way to reduce the growth rate is to allow horses and burros to self-limit. As reviewed in Chapter 3, few scientific studies have been conducted on equid self-limitation. However, there is substantial evidence in wild ungulate populations that self-limitation will involve shortages of forage and water for the population, which will increase the number of animals that are in poor body condition and dying, either directly from lack of food and water or indirectly from increased vulnerability to disease. Although increased mortality would reduce population growth rates, it is unclear how much the growth rate would be lowered and what effect this strategy would have on the health of the rangeland and on the welfare of other animals on the range. Without further research, experimentation, and modeling exercises, it is difficult to predict mortality, body conditions of all animals, and rangeland ecological conditions at the point of horse and burro self-limitation.
An issue that is vitally important for improving the operation and the image of the Wild Horse and Burro Program is the connection of the establishment of AMLs to results of scientific research. AMLs involve policies that allocate rangeland resources among many uses of the land, but information regarding the interaction of horses and burros with the environment and other species, which informs these policies, should be robust and of the best quality possible. The committee suggests that a science-based assessment of the range and the interaction of animals with the range, consistently applied over time and among districts, could inform the establishment of AMLs more accurately. The committee could not identify a science-based rationale used by BLM to allocate forage and habitat resources to various uses within the constraints of protecting rangeland health and listed species and given the multiple-use mandate.
The committee also finds that, if AMLs remain set at their 2012 levels (Appendix E, Table E-1), contraception or self-limitation strategies may not reduce horse and burro populations to target levels. To manage horses at 2012 AMLs, horses may first have to be removed. Large-scale removal would require the public to accept gathers on a number of HMAs over a short period, probably within less than 5 years, which would be expensive.
Once horses were removed, this approach would also require the culling of thousands of animals or the warehousing of many more thousands of horses in long-term holding. If contraception or self-limitation strategies could curtail population growth rates after a large-scale removal, the costs of long-term holding would eventually decline as fewer horses were placed into these facilities and the horses in holding would eventually leave through sale or death.
In most HMAs managed for populations of burros, 2012 AMLs were exceeded. However, the total population of burros is much smaller than that of horses; in 2012, BLM reported 5,841 burros in HMAs. That number needs to be verified with appropriate survey methods, but if it is accurate, removing burros permanently from the range could jeopardize the genetic health of the total population. The burro population is more fragmented than the horse population. Burro HMAs exist in five states; no state-aggregated AML exceeds 1,500 burros; and the cumulative, program-wide AML for burros is 2,923. Translocation of burros between HMAs would need to occur more often than it would for horses to compensate for the geographic fragmentation and small size of the population. BLM may also need to assess whether the AMLs set for burros can sustain a genetically healthy total population. It is possible that a more accurate population estimate could reveal that there are already enough previously unaccounted-for animals on the range to support genetic health at the total population level. However, if more animals were needed to sustain a healthy population, burros from HMAs that are above their AMLs could be relocated to HMAs that have AMLs set for burros but few or no animals on them.
Cultivating Public Confidence
A statement that the committee heard often in public comment sessions was that the public has no confidence in the information that BLM provides about the Wild Horse and Burro Program. Skepticism of BLM’s credibility applied to all aspects of the program, including population estimates and population growth rates, genetic health of the animals, consequences of population-control strategies, AML establishment, and public-land allocation to free-ranging horses and burros.
The committee acknowledges that science cannot transform how BLM is perceived by all members of the public. However, having a scientific underpinning for its decisions would help BLM to explain and defend its management actions. For example, improving the accuracy and quantifying the uncertainty of population estimates would allow BLM to respond with data to criticism about the numbers of equids that it reports on public lands. Recording information on genetics and on animals treated with contraception would strengthen input data for models and thereby increase their predictive power with respect to the effects of management actions, such as translocation and contraceptive treatment. Even in decisions that are largely policy-driven management decisions, such as the proportion of rangeland resources that should be allocated to horses or burros, science-based information about forage availability can help BLM to explain one of the constraints underlying forage-allocation decisions.
Making the data that it collects available to the public would also be an opportunity to increase public confidence that BLM could explore. For example, improving population estimates through statistically rigorous survey methods probably will not enhance public confidence in the agency unless the methods and the numbers produced by the surveys are made available to the public. The committee is aware that BLM has already taken steps toward creating such a database. Fully populating the database on a timely and routine basis and making it accessible to the public is an example of an action that BLM could take
to increase the transparency of its decisions. Another opportunity would be to include in gathering plans and environmental assessments a clear explanation of how models are used to inform management decisions. Finally, BLM districts need resources and training to develop consistently applied monitoring and allocation methods. Investment in BLM’s own human capital through training, interaction with professional and research organizations, and interaction throughout the agency is needed as a foundation for improved and consistently applied methods.
Greater public participation in BLM decision-making and data-gathering could increase public confidence in agency actions, and the committee recommends the analytic-deliberative approach to engaging the public in management decisions and increasing trust through transparency. Social-science research may help to identify opportunities and improved processes for cooperation between BLM and the public. Finally, citizen-scientist reports could be used to bolster BLM-collected data on sentinel populations and rangeland conditions.
The committee believes that the tools suggested above would entail more intensive management of horses and burros than it observed during its review of the Wild Horse and Burro Program. The horses at Assateague Island in Maryland and at Shackleford Banks in North Carolina are not subject to the Wild Free-Roaming Horses and Burros Act (P.L. 92-195), but intensive management has proved successful on these islands. Those locations have advantages over many BLM HMAs from a management perspective in that the animals are confined to discrete spaces and the herds are small enough for each animal to be uniquely identified. Nevertheless, they stand as scientifically studied examples of how intensive management can work and what effects BLM could expect from reducing population size and implementing contraception more consistently and widely. As has been seen on Assateague Island and Shackleford Banks, fertility control can help to stabilize population size (Kirkpatrick and Turner, 2008; S. Stuska, National Park Service, email communication, November 1, 2012). Such an outcome on BLM HMAs could be achieved with intensive management if contraceptives were applied every year, as is the case on eastern barrier islands. Although more frequent gathers would be required to achieve similar results on large HMAs in the western United States, any application of contraceptives or chemical vasectomies to a large percentage of horses in a gather would reduce the growth rate and thus the number of horses that BLM would have to remove to meet management goals.
The committee recognizes that the multipronged approach of science-based tools that it is proposing would require substantial financial resources from BLM in the short term. It therefore recommends the identification of sentinel populations and HMAs. As suggested in Chapter 2, select HMAs representative of diverse ecological settings could be studied more intensively to improve assessment of population dynamics and ecosystem responses to changes in animal density, management interventions, and variation in seasonal weather and trends in climate. The results of such studies could be used to inform population and ecosystem modeling efforts for HMAs that have similar characteristics. Selecting sentinel HMAs would be more cost-effective than studying every herd, and it is a scientifically sound strategy. The committee views the population and ecosystem research conducted by USGS on the HMAs of Little Book Cliffs, McCullough Peaks, and Pryor Mountains as a step in that direction and encourages BLM to continue working with USGS and perhaps ecologists in academic institutions on the identification of and research on representative HMAs for both horses and burros.
That complex, intensive approach would substantially benefit from a commitment by BLM to support an integrated team of competent, dedicated scientists. Cooperation among reproductive experts, animal behavior specialists, rangeland and ecosystem scientists, wildlife population modelers and demographers, and geneticists would help to achieve the program’s goals. By supporting such a team, BLM would be able to generate the scientific data needed to inform, explain, and defend management decisions.
Furthermore, as recommended strongly by the National Research Council Committee on Wild and Free-Roaming Horses and Burros in its 1980 and 1982 reports and by the authoring committee of this report, using social science to proactively identify issues that may cause tension with parties interested in horses, burros, and the multiple uses of public lands could help BLM to address some of the criticisms expressed to the committee by members of the public. Increasing the transparency of data used to inform management decisions would probably also improve how the agency is perceived by the public.
In the short term, more intensive management of free-ranging horses and burros would be expensive. However, addressing the problem immediately with a long-term view is probably a more affordable option than continuing to remove horses to long-term holding facilities. The committee recognizes that for over 40 years BLM has managed horses and burros in an environment in which there are often incongruent mandates and mandates not accompanied by the required financial resources, attempting to manage the land for multiple uses (including but not limited to free-ranging horses and burros), to preserve a thriving natural ecological balance, to prevent rangeland deterioration, and to respond to concerns voiced by a variety of stakeholders. Meeting those myriad, and often conflicting, demands may not be possible. At the time the committee was preparing its report, BLM districts seemed to be struggling with many of these demands independently. However, there are steps that BLM can take and, in some cases has already taken (such as its work with USGS), that could help the agency to address its mandates more successfully. Further investment in science-based management approaches and in helping districts to apply them consistently cannot solve the problem instantly, but it could lead the Wild Horse and Burro Program to a more financially sustainable path that manages healthy horses and burros with greater public confidence.
BLM (Bureau of Land Management). 2012. Minutes of the National Wild Horse and Burro Advisory Board Meeting, April 23-24, Reno, NV.
Bolstad, D. 2011. Wild Horse and Burro Program. Presentation to the National Academy of Sciences’ Committee to Review the Bureau of Land Management Wild Horse and Burro Management Program, October 27, Reno, NV.
GAO (U.S. Government Accountability Office). 2008. Effective Long-Term Options Needed to Manage Unadoptable Wild Horses. Washington, DC: U.S. Government Accountability Office.
Kirkpatrick, J.F. and A. Turner. 2008. Achieving population goals in a long-lived wildlife species (Equus caballus) with contraception. Wildlife Research 35:513-519.
NRC (National Research Council). 1980. Wild and Free-Roaming Horses and Burros: Current Knowledge and Recommended Research. Phase I Final Report. Washington, DC: National Academy Press.
NRC (National Research Council). 1982. Wild and Free-Roaming Horses and Burros. Final Report. Washington, DC: National Academy Press.