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Sponsored by The Humane Society of the United States (HSUS), The Annenberg Foundation and the Bureau of Land Management (BLM), the Wild Horse Symposium was held in Jackson Hole, WY on August 28, 2012. Leading researchers, field workers and others presented the most up-to-date scientific, regulatory, and practical developments in the use of reversible contraceptives to manage wild horse and burro populations during the day-long meeting. Below are some highlights from the Symposium:
The wild horses living on the Maryland side of the Assateague National Seashore are "free-roaming wildlife," living in natural wild horse bands. Managed by the National Park Service, the Assateague herd is living proof that use of the safe and humane porcine zona pellucida (PZP) fertility control vaccine can effectively suppress population growth and eliminate the need for removals, even on a small island with limited habitat. The Assateague herd on the Maryland side of the island has been managed for the past 14 years without the removal of any horses. Wild horses born on Assateague are able to live and die naturally without threat of capture and removal. In contrast to this management model, the horses on the Virginia side of the island are privately owned, live in large fenced enclosures and graze on the Chincoteague National Wildlife Refuge. On this end of the barrier island, PZP is not utilized to suppress population growth, and so dozens of foals are removed from the herd annually in order to manage the herd size.
At the symposium, Carl Zimmerman, the Park Service resource specialist responsible for overseeing the island's wild horse program for many years, discussed how the availability of the PZP vaccine allowed the Park Service to balance the need to control wild horse population growth while respecting the public's desire to avoid removing any horses from the island. During Zimmerman's presentation the theme of PATIENCE repeatedly surfaced. While zero population growth was achieved within two years of beginning the PZP program, reducing the horse population to the desired number took more time.
Thanks to the dedication of Park Service employees (primarily Zimmerman and Allison Turner), and to the leadership, vision and expertise of Dr. Jay Kirkpatrick, director of Center for Science and Conservation in Montana, the hard work of annually darting the mares with the vaccine was undertaken and success was achieved. Despite the fact that horses on birth control live longer, healthier lives (due to the decreased foaling), the Assateague population was reduced from 175 horses to 135 within 11 years. PZP fertility control provided the mechanism for the Park Service to realize its vision of managing wild horses as wildlife in order to maintain their wild behaviors. Extensive genetic testing allows the Park Service to ensure high genetic variability and the long-term health of the herd. To read more about this model program please click here.
Return to Freedom (RTF) American Wild Horse Sanctuary in Lompoc, California has, for the past 15 years, successfully been using PZP (one year application) to suppress population growth while maintaining natural wild horse herd dynamics. Founder Neda DeMayo (left) has made respect for and preservation of the natural social structures and society of wild horses a foundation of the RTF program. At the symposium, DeMayo presented the results of RTF's decade-long fertility control program and highlighted the way in which PZP has allowed RTF to stay true to its vision and goals while managing horses on a nearly 400-acre property in Santa Barbara County, California. RTF presently provides sanctuary to nearly 400 wild horses rescued from BLM and U.S. Fish and Wildlife Service roundups.
HSUS, in conjunction with the BLM, has embarked on a four-year study of the use of PZP-22 (the two-year formulation of PZP) in Colorado's Sand Wash Basin Herd Management Area (HMA) and Utah's Cedar Mountains HMA. During the course of the study, HSUS field researcher Kayla Grams studied the behavioral impact of PZP on the natural, wild behaviors of the mustangs. She carefully documented the behaviors of hundreds of horses in the study program and noted that the behavioral impacts of PZP were minimal to nonexistent. Study and documentation of the family bands showed that fidelity of individual mares to stallions was not decreased after application of the drug. This is important information that further supports PZP as a humane alternative to the current system of removing wild horses from the range. Preserving the natural, free-roaming behaviors of wild horses is fundamental to protecting and preserving these animals. While intervention of any kind is not desirable, if population suppression must to take place the "minimal feasible level" of any management policy is not only desirable but actually is required under the Wild Free-Roaming Horses and Burros Act. The efficacy results of the PZP-22 application in the two herds were presented. While results were not optimal, significant reductions in birthing rates did occur each year. Future adjustments of the delivery mechanism and timing of application should enhance the efficacy of the PZP-22 form of the vaccine.
Dr. Charles DeSeve presented an economic model that highlighted how the use of PZP could, if used appropriately, suppress wild horse population growth. He presented a detailed economic-based model that provides the BLM with a planning tool that would allow the agency to (1) stop stockpiling wild horses in government holding facilities (like the one at right) and keep them living naturally on the range; and (2) save more than $200 million over 10 years by using on-the-range management instead of the current, unsustainable roundup-remove-warehouse approach. The BLM's Al Shepherd, BLM Nevada Wild Horse and Burro State Lead, noted that until a longer- lasting fertility control drug is available, removals will continue to be necessary. Joan Guilfoyle, Wild Horse and Burro Program Chief, indicated that the agency still plans to implement gelding and use other tools "that people in this room will not like." Drugs that may cause permanent sterilization, behavioral changes and other health problems are among the controversial "tools" to which Guilfoyle was likely referring.
Native PZP, pioneered and developed by Dr. Jay Kirkpatrick and the Science and Conservation Center in Montana, was recently approved for use in horses by the Environmental Protection Agency (EPA) under the name ZonaStat-H. After years of discussion, the Food and Drug Administration (FDA) and EPA decided that, because PZP is to be dispensed to wild animals, there is a potential impact to the environment. Therefore, the EPA has been designated as the agency responsible for drug review and approval. The EPA has classified PZP-22 as a "pesticide," a decision that drew sharp criticism from the audience due to the implication that wild horses are "pests." However, an EPA representative attending the meeting explained that, while the word "pesticide" did refer to any non-human animal that could negatively impact the environment (via overpopulation, etc), the use of the word was fundamentally a legal issue. In fact, the only regulatory framework available for approval of immunocontraception for use in wildlife is under the pesticide designation. GonaCon, a hormonal fertility control drug developed by the U.S. Department of Agriculture's (USDA's) National Wildlife Research Center (NWRC), was discussed by Kathy Fagerstone of the USDA/NWRC. Fagerstone explained that the USDA has applied for EPA approval of Gonacon for use in wild horses. She said that EPA approval was expected next year. Gonacon interferes with the pituitary's ability to produce reproductive hormones, which then trigger the release of other hormones related to reproduction. A National Park Service-sponsored test of GonaCon on wild horses is ongoing in Theodore Roosevelt National Park in North Dakota. Fagerstone indicated that studies showed no to limited impacts to natural behaviors, despite the drug being hormone based; Fagerstone said that behavioral data would be published in the future. Additional studies about the use of immunocontraception on wildlife, including wild horses, and fertility control drugs was presented on the days following the symposium at the 7th International Conference on Fertility Control in Wildlife (August 29-31, 2012).