Wild Horse Symposium: Insights from August 28, 2012
The Wild Horse Symposium, sponsored by The Humane Society of the United States (HSUS), The Annenberg Foundation, and the Bureau of Land Management (BLM), took place in Jackson Hole, WY, on August 28, 2012. This event brought together leading researchers, field workers, and other experts to discuss the latest scientific, regulatory, and practical advancements in using reversible contraceptives to manage wild horse and burro populations. Here are some highlights from the symposium:
Model Management Program: Wild Horse Herds of Assateague National Seashore
The wild horses 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 demonstrates that the 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. For the past 14 years, the Assateague herd has been managed without removing any horses, allowing them to live and die naturally without the threat of capture and removal.
In contrast, 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. Here, PZP is not used, resulting in the annual removal of dozens of foals to manage the herd size.
Lessons in Patience
At the symposium, Carl Zimmerman, the Park Service resource specialist overseeing the island's wild horse program, discussed how the PZP vaccine allowed the Park Service to balance population control with the public's desire to avoid removing horses. The theme of patience was emphasized throughout Zimmerman's presentation. While zero population growth was achieved within two years of starting the PZP program, reducing the horse population to the desired number took more time.
Thanks to the dedication of Park Service employees, particularly Zimmerman and Allison Turner, and the leadership of Dr. Jay Kirkpatrick, director of the Center for Science and Conservation in Montana, the hard work of annually darting the mares with the vaccine was undertaken successfully. Despite horses on birth control living longer, healthier lives, the Assateague population was reduced from 175 horses to 135 within 11 years. PZP fertility control enabled the Park Service to manage wild horses as wildlife, maintaining their wild behaviors. Extensive genetic testing ensures high genetic variability and the long-term health of the herd.
Sanctuary: Wild Horses & PZP
Return to Freedom (RTF) American Wild Horse Sanctuary in Lompoc, California, has successfully used PZP for 15 years to suppress population growth while maintaining natural wild horse herd dynamics. Founder Neda DeMayo has made respect for and preservation of the natural social structures of wild horses a foundation of the RTF program. At the symposium, DeMayo presented the results of RTF's fertility control program, highlighting how PZP has allowed RTF to stay true to its vision while managing horses on a nearly 400-acre property in Santa Barbara County, California. RTF provides sanctuary to nearly 400 wild horses rescued from BLM and U.S. Fish and Wildlife Service roundups.
Behavioral Impacts Matter: HSUS Research Study in Sand Wash Basin and Cedar Mountains
HSUS, in conjunction with the BLM, has embarked on a four-year study of PZP-22 in Colorado's Sand Wash Basin Herd Management Area (HMA) and Utah's Cedar Mountains HMA. HSUS field researcher Kayla Grams studied the behavioral impact of PZP on the natural behaviors of the mustangs, documenting that the behavioral impacts of PZP were minimal to nonexistent. The study showed that fidelity of individual mares to stallions was not decreased after application of the drug, supporting PZP as a humane alternative to removing wild horses from the range.
Preserving the natural, free-roaming behaviors of wild horses is fundamental to their protection. While intervention is not desirable, if population suppression must occur, the "minimal feasible level" of management is required under the Wild Free-Roaming Horses and Burros Act. The efficacy results of PZP-22 in the two herds were presented, showing significant reductions in birthing rates each year. Future adjustments in delivery and timing should enhance the efficacy of PZP-22.
Economics: Ending Removals and Humanely Managing Wild Horses on the Range
Dr. Charles DeSeve presented an economic model demonstrating how PZP could suppress wild horse population growth if used appropriately. His model provides the BLM with a tool to stop stockpiling wild horses in government facilities and keep them on the range, potentially saving over $200 million over 10 years. However, BLM's Al Shepherd noted that until a longer-lasting fertility control drug is available, removals will continue. Joan Guilfoyle, Wild Horse and Burro Program Chief, indicated that the agency plans to implement gelding and other controversial tools, which may include drugs causing permanent sterilization and behavioral changes.
Regulatory Pipeline: EPA Approves PZP and GonaCon EPA Approval Pending
Native PZP, developed by Dr. Jay Kirkpatrick and the Science and Conservation Center in Montana, was approved for use in horses by the Environmental Protection Agency (EPA) under the name ZonaStat-H. The EPA has classified PZP-22 as a "pesticide," a decision criticized for implying wild horses are "pests." However, this classification is a legal issue, as the only regulatory framework for immunocontraception approval is under the pesticide designation.
GonaCon, a hormonal fertility control drug developed by the USDA's National Wildlife Research Center, is pending EPA approval for use in wild horses. Kathy Fagerstone of the USDA/NWRC explained that GonaCon interferes with reproductive hormone production, with studies showing limited impacts on natural behaviors. Additional studies on immunocontraception and fertility control drugs were presented at the 7th International Conference on Fertility Control in Wildlife.