Wild-horse advocates urge birth-control program

June 6, 2016 - Some three dozen wild-horse groups are citing the success of fertility control vaccine programs in western Colorado in urging much more widespread use of such programs as an alternative to rounding up and caring for excess horses.

Thirty-five groups ranging from the American Wild Horse Preservation Campaign to the Humane Society of the United States issued the call last week. Their action comes after the Bureau of Land Management said last month that the number of wild horses and burros on public rangelands grew by an estimated 15 percent last year and the cost of caring for the 46,000 wild horses and burros that have been captured and placed in corrals and pastures will be about $1 billion over their lifetimes.

The advocacy groups argue that increased use of the PZP vaccine is a humane and cost-effective way of heading off that fiscal crisis. They specifically cite the success of the approach in places such as the Little Book Cliffs wild horse range near Grand Junction and Spring Creek Basin in southwest Colorado, and by the National Park Service at Assateague Island National Seashore on the East Coast.

The groups say 70 percent of the BLM’s wild horse and burro program budget is spent on roundups and removals, and less than 1 percent on humane and effective fertility control.

“It is literally the only acceptable tool they have now to control population growth. The fact that they continue not to use it (more) is inexplicable,” said Suzanne Roy, executive director of the American Wild Horse Preservation Campaign.

BLM officials agree about the success of the programs in certain situations. But the agency also points to challenges in replicating the success of the PZP vaccine program in other ranges, such as where horse herds are spread out over large areas and are harder to dart using guns.

Said Tom Gorey, a spokesman with BLM’s national office, “The overall goal of the BLM’s Wild Horse and Burro Program is to ensure that healthy wild horses and burros thrive on healthy public rangelands.

“The BLM is committed to applying PZP to the maximum extent feasible, and is open to new public-private partnerships that would expand the use of this vaccine.

“The principal limitations on expanding PZP are logistical and budgetary. The cost of rounding up and treating horses with PZP would be roughly $55 million each year. These costs would be on top of the roughly $80 million already being spent to support wild horses and burro management.”

Roy says a dart carrying a dose of the vaccine costs $27. The cost for the vaccine program would go up if bait-trapping of horses is required to vaccinate ones that can’t be darted with guns, but she still thinks the cost is less than removing horses and putting them in holding facilities.

“It just needs to be implemented more aggressively by the BLM,” she said.


Marty Felix, who darts Little Book Cliffs horses with the vaccine as a volunteer with the local Friends of the Mustangs nonprofit group, said the group doesn’t take political positions and didn’t join the groups that recently pressed the BLM on the vaccine issue. But she personally agrees with the groups’ position calling for increased use of vaccine.

She said she realizes the challenges that might exist in administering the vaccine to more spread-out horse herds that also may be wilder and harder to approach than the local horses.

But she added, “I think it’s better than having 40,000 or 50,000 in holding pens for the rest of their miserable lives.”

The BLM says that 67,000 wild horses and burros currently roam the West, more than twice the number recommended by BLM management plans. There are about 1,530 wild horses in Colorado, nearly twice what the agency considers the appropriate management level in the state. The agency worries that too many of the animals on the land will lead to problems such as overgrazing, and it also is under pressure to control numbers from ranchers whose livestock also graze on public land.

But some horse advocates object to roundups that split up herds and can lead to injuries and deaths. And while the BLM was able to adopt out nearly 8,000 rounded-up horses a year in the early 2000s, that number is down to about 2,500 horses a year due to factors such as the Great Recession.

Some of the other measures the BLM is now proposing include getting legislative authority to transfer horses to other federal agencies needing work horses. One horse advocacy group, the Cloud Foundation, fears the proposed legislation could lead to such horses losing protections provided by current law and being sold to slaughter.



Amid all the challenges and controversy surrounding the Wild Horse and Burro Program, the PZP vaccine approach has provided a bright spot, at least in certain situations. The vaccine works with a mare’s immune system to produce antibodies that block sperm receptor sites on the membrane surrounding the ovum. It’s nonhormonal, so it doesn’t affect horses’ endocrine systems or natural behavior.

Local BLM spokesman Chris Joyner said the Little Book Cliffs program began in 2002, with the volunteer darters from Friends of the Mustang playing a major role. He said the vaccine has been between 80 percent and 90 percent effective annually in keeping treated mares from becoming pregnant.

The BLM still has population growth of between 8 percent and 15 percent in the Little Book Cliffs, and has held roundups there in 2004, 2007 and 2013. But before PZP use it was gathering and removing horses there every two to three years, he said.

At Spring Creek Basin, the BLM and volunteers have administered PZP for five years. The agency says it has successfully maintained the herd size since the last gather in 2011 and doesn’t anticipate more gathers there in the near future.

Horse advocates say the McCullough Peaks program in Wyoming has within three years all but eliminated growth of the wild horse population there.

The coalition of horse advocacy groups points to a National Academy of Sciences study recommending the use of PZP as a more affordable alternative to removing horses and keeping them in holding facilities. The study also argued that removal likely facilitates high rates of population growth among wild horse herds, maximizing the number that must be removed.



The PZP approach has limitations. One type of the vaccine is designed to last just a year and requires a booster vaccine a few weeks after the first one. Another that was designed to be effective longer doesn’t require a booster but Roy said it hasn’t proven to be much longer-lasting in blocking fertility. She said work continues on research into longer-lasting vaccines.

Advocacy groups say that because the vaccine isn’t permanent, it enables managers to monitor a herd’s population and allow for more births as appropriate.

Gorey said that most of the BLM’s herd management areas, because of their size and their horses’ wary nature, wouldn’t allow for darting horses.

“So the animals would have to be captured, treated and released,” he said.

Bait-trapping can involve use of water or food to lure horses to trap areas. Gorey said that can be viable where water is limited, but most areas are large enough that horses can find another watering hole.

Joyner said the success of the Little Book Cliffs program is high thanks to “amazing volunteers” who keep meticulous records on the horses, helping darters plan which mares to dart and identify previously darted horses. Felix said that in the case of larger herds where there aren’t people such as volunteers who can recognize individual animals, there would be a need to mark horses through a method such as freeze branding to track which ones have been treated or need treating.

Joyner said some of the Little Book Cliff horses also are habituated to people and let people get within the 50 yards needed to dart them. He said he’s seen other horses in northwest Colorado, and even within the Little Book Cliffs, that bolt when he’s even 500 yards away, and they would be difficult to dart.

“So even within the same Herd Management Area our darting success can range based on horse behavior,” he said.

He’s also seen mixed results locally with use of bait traps during gathers. Success has depended on the degree to which natural water and food sources competed with water and food bait. Joyner said those natural source conditions can change over a matter of days, and bait traps also are labor- and resource-intensive. Also, some horses are spooked just by the scent of staff monitoring the traps, he said.

While Roy and Felix understand the greater difficulty in using the vaccine in some circumstances, they think the BLM needs to show more open-mindedness and creative thinking by trying to broaden the approach’s use. Roy thinks the agency’s bureaucracy and culture is standing in its way, and she sees differences among local-level BLM approaches in what is a decentralized agency.

“I think there has to be a national directive from BLM to local offices to say, ‘Look, this is the approach we want you to take,’ ” she said.

Felix said there currently are cases of smaller herd ranges where volunteers are willing to dart horses but are being rebuffed.

“The BLM or somebody is standing in their way and saying, ‘Uh-uh,’ or, ‘We have to think about it,’ ” she said.

Callie Hendrickson is executive director of the White River and Douglas Creek conservation districts in Rio Blanco County. She said conservation districts and the ranching community are concerned about rangeland health. She said she thinks everyone supports fertility control, but for a PZP program to work, it requires a small herd, fairly gentle horses and volunteers willing to do the work each year.

She said that more generally, fertility control isn’t enough in cases when herds are larger than the BLM’s designated appropriate size.

In those cases, “you can’t fertility control your way out of it. You have to remove horses first,” she said.

Originally published June 6, 2016, in the Grand Junction (Colo.) Daily Sentinel

Do you like this post?
Information: Animal Fertility Control Vaccine
Learn more about managing wildlife with fertility vaccine