The natural world is managed by food supply and predation. Unfortunately, America’s vast rangelands are fenced for livestock and natural predator populations are under constant siege from livestock ranchers, hunting, and poaching.

At Return to Freedom, our goal is to minimize the need for costly and traumatic roundups, as well as save millions of tax dollars, while ensuring natural selection and genetic diversity by slowing down reproduction as opposed to stopping it all together or removing wild horses and burros from the range. Our mission includes:

  • maintaining natural social and harem bands to allow natural social behavior
  • exploring minimally invasive wild horse management that can be applied on the range

To that end, RTF had six herd management options:

  • Option 1: No management (increasing population)
  • Option 2: Adoption or sale (to address increasing population)
  • Option 3: Permanent sterilization of stallions (permanent/affects behavior)
  • Option 4: Permanent sterilization of mares (permanent/affects behavior)
  • Option 5: Separation (permanent/affects behavior)
  • Option 6: Contraception (reversible, allows natural social bands)

After examining all options, #6, fertility control was selected at RTF as the least invasive approach.

Education is a primary goal of Return to Freedom’s mission. Our sanctuary was created not only as a model to explore solutions for wild horse and burro management that could be applied on the range (as an alternative to the capture, removal, and warehousing of wild horses and burros), but also as a venue to appreciate and observe natural horse behaviors. With over 22 years of data, Native PZP was a proven effective and humane method to make this possible. In 1999, RTF reached out to Dr. Jay Kirkpatrick, Director of The Science and Conservation Center in Billings, Montana. Under his guidance, RTF has been able to manage herd populations at the Sanctuary utilizing the native PZP vaccine — a non-hormonal, reversible fertility control, effective for slowing down reproduction in wild mammals.

Because it is non-hormonal, it does not:

  • affect the endocrine system or natural behaviors
  • create negative health side effects
  • enter the food chain, harming other wildlife

In order to allow our horses to live as natural a lifestyle as we can provide, wild horse bands at Return to Freedom are managed with native PZP. This allows the natural hormone-driven movement and behaviors which are necessary for the horses’ well being physically and emotionally while blocking fertilization.

Not all mares respond to the vaccine (non-responders) and a small percentage of mares who had been responding to the vaccine for 6-7 years, and were taken off the program, have foaled again. So fears of native PZP eradicating herds have been proven moot. In this way, the vaccine becomes a tool to slow down reproduction and avoid adoption, separation, or permanent sterilization.

Our data, presented at the 2012 Wild Horse Symposium in Jackson Hole, WY, shows that RTF’s birth control program has an efficacy rate of about 85-91%. Currently, all fertile mares housed with band stallions are on birth control.

Even if the BLM could administer the vaccine to every mare on federal lands, it would not be possible to zero out herds with this method. Unfortunately, BLM has been more focused on permanent sterilization to achieve its desired low-population goals, and it has been an uphill challenge to engage the agency in increasing the use of this benign vaccine to manage the horses on the range where they rightfully belong.


News About Wild Horse and Burro Population Control