AWHC Position Statement on Fertility Control

Wild horses in the United States no longer have free-range over vast western rangelands. Instead, pursuant to the Wild Free-Roaming Horses and Burros Act (1971, as amended), they are confined to Herd Management Areas (HMAs) or Wild Horse Territories (WHTs) on public lands that are managed by the Bureau of Land Management (BLM) or U.S. Forest Service (USFS) for "multiple uses." Such uses include commercial industries like livestock grazing, oil and gas extraction and mining, as well as recreational pursuits, including wildlife watching, ATV use, hunting and fishing. Although mountain lions and wolves can and do prey on wild horse foals, due to hunting and government predator “control” or kill programs, these species are not present in sufficient numbers to regulate wild horse populations, except in a small number of areas.

The BLM is mandated to manage public lands for multiple uses, and is not permitted to allow the range to deteriorate. If left unmanaged, wild horse populations might eventually stabilize near what is known as their food-limited ecological carrying capacity. However, reaching this level would result in deteriorated range conditions that are ecologically unsound.

The conditions that America's mustangs live in today are anything but natural. The vast majority of wild horse populations have been genetically manipulated and socially and behaviorally disrupted by a constant cycle of roundups and removals. Their ability to migrate freely to adjust to changing environmental conditions is inhibited by fences that confine them to artificial habitats known as HMAs or WHTs. They must compete on our public lands with other uses backed by powerful economic interests. Under these circumstances, the ideal of natural regulation is just that: an ideal that is divorced from reality.

The AWHC coalition’s goals include securing a fairer share of resources for wild horses on our public lands, and protecting predators in order to restore a more natural ecological balance on western rangelands. However, we also must also deal with modern realities, which means that wild horse population growth on our public lands must be managed in some form. The question then becomes which form of management available today is the most humane, minimally intrusive and preserves natural behaviors?

The answer today is PZP fertility control. This proven technology provides a safe, humane, cost-efficient and effective alternative to the current wild horse management approach of roundup, removal and stockpiling of horses in government holding facilities.

The PZP vaccine, now registered with the Environmental Protection Agency (EPA) as ZonaStat-H, has a decades-long history of use in multiple wildlife species, including wild horses. The vaccine produces an immunological response that prevents fertilization. Since it does not affect hormone production, the impacts to behavior are minimal, particularly when compared to the alternatives. The vaccine is also reversible. It is being used to safely and effectively manage wild horses in the U.S. today. In the Assateague Island National Seashore, the National Park Service has used PZP to manage a wild horse population for over two decades without a single removal of a horse. 

The PZP vaccine is not a pesticide. It is an extremely well-vetted immunocontraceptive vaccine that has been used for 40 years in many wildlife species including wild horses. The Food and Drug Administration (FDA) turned registration of the vaccine over to the EPA, since it was developed for use in the environment on a wildlife species (wild horses). Since the EPA has no category for "wildlife contraception," it processed PZP under the “pesticide” category as the only available process for registering the vaccine for use. The label is purely bureaucratic; it has no scientific or practical meaning. The PZP vaccine is produced by the non-profit Science and Conservation Center, which pioneered its use in wildlife and provides it to the BLM and other entities at a financial loss.

When compared to the alternatives presently employed or being considered by the federal government – traumatic roundups and mass removal of horses from their homes on the range; surgical sterilization (castration of stallions and spaying of mares) that destroys natural behaviors; experimental contraceptives that impact behavior and may have serious side effects – the PZP vaccine is clearly the superior alternative currently available for humane management of wild horse herds.