WASHINGTON -- The U.S. Bureau of Land Management's (BLM) current practice of removing free-ranging horses from public lands promotes a high population growth rate, and maintaining them in long-term holding facilities is both economically unsustainable and incongruent with public expectations, says a new report by the National Research Council. The report says that tools already exist for BLM to better manage horses and burros on healthy ecosystems, enhance public engagement and confidence, and make the program more financially sustainable. It also provides evidence-based approaches that, if widely and consistently implemented, can improve the management of these animals on public lands in the western U.S.
The committee that wrote the report determined that most free-ranging horse populations are growing at 15 percent to 20 percent a year, meaning these populations could double in four years and triple in six years. With no intervention by BLM, the horse population will increase to the point of self-limitation, where both degradation of the land and high rates of horse mortality will occur due to inadequate forage and water. In addition, periodic droughts, many of them severe, in the western public lands cause immediate and often unpredicted impacts. There is little if any public support for allowing these impacts on either the horse population or the land to take place, and both go against BLM's program mission. However, the current removal strategy used by BLM perpetuates the overpopulation problem by maintaining the number of animals at levels below the carrying capacity of the land, protecting the rangeland and the horse population in the short term but resulting in continually high population growth and exacerbating the long-term problem.
To manage horse populations without periodic removals, widespread and consistent application of fertility control would be required, the committee determined. Three methods in particular -- porcine zona pellucida (PZP) and GonaCon for mares and chemical vasectomy for stallions -- were identified as effective approaches.
"The committee recommended these approaches based on the evidence of their efficacy with other populations, notably the horses on Assateague Island, but cautioned that scaling up use of these methods to the larger and more disseminated horse populations in the western U.S. will be challenging," said Guy Palmer, a veterinarian with Washington State University and chair of the study committee.
The committee also strongly recommended that BLM improve and standardize its methodology to estimate population size, stressing the importance of accurate counts as the basis for all management strategies. A large body of scientific literature suggests that the proportion of animals missed in current surveys ranges from 10 percent to 50 percent.
Additionally, an examination of the genetics and health of population groups as well as of the range lands they occupy can be used to assure that both the animal populations and the ecosystem are being appropriately managed. Developing an iterative process whereby public participants could engage with BLM personnel scientists on data gathering and assessment would increase the transparency, quality, and acceptance of BLM's decision-making process.
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| Contact: Lorin Hancock news@nas.edu 202-334-2138 National Academy of Sciences Source:Eurekalert |
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