Population Management

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

Return to Freedom does not endorse the argument that there is an over-population of wild horses and burros.  While livestock graze on 160 million acres of BLM- managed lands, wild horses and burros are consigned to only 26.9 million acres, just 11% of our public lands, where they are out-numbered by millions of privately owned livestock by an average ratio of 50:1.

Return to Freedom endorses the protection of predators to naturally manage large mammal populations in wilderness areas. Unfortunately, this has not been accepted as a viable argument in the current political paradigm due to livestock management and urban encroachment.

Only to the extent population control is necessary, fertility control methods are available whose efficiency has been proven safe, humane and effective as an alternative to permanent sterilization, capture, removal or shooting. Native PZP should only be used judiciously, solely to the extent necessary to maintain healthy population levels, in keeping with the original spirit and intent of the 1971 Act. The goal is to minimize the need for costly and traumatic round-ups 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.

At Return to Freedom’s American Wild Horse Sanctuary, the 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 6 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, RTF’s American Wild Horse 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, a non-hormonal immuno-contraception. This allows the natural hormone-driven movement and behaviors which are necessary for the horse’s 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 their 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.

For more detailed information:

Myths and Facts – Native PZP (First Edition 02-28-2015; updated 05-08-15x)FINAL

PZP Q&A (Fourth Edition, June 6 2012)(Master Word File)FINAL

Animal Fertility Control Vaccine

Contraceptive vaccines-wildlife 2011

article-wildlife contraception-07