Contraception helps manage herd

Summer drought was a concern for Disappointment wild horses

The magic of the West is still alive and well in the form of the mustangs of Disappointment Valley.

One year after a large-scale roundup sponsored by the Bureau of Land Management, roughly 50 wild mustangs still roam the dusty range on 22,000 dedicated acres north of Dove Creek. With manes flying in the wind and hooves beating the hard earth, the horses have once again laid claim to the land and continue to thrive despite harsh conditions and the unpredictable nature of nature itself.

“The herd is doing really, really well,” said Shannon Borders, public information specialist for BLM’s Southwest District. “We are really happy to see the success of this group of mustangs.”

The gather a year ago was part of a herd-reduction effort by the U.S. Bureau of Land Management designed to maintain a healthy herd and range. Of the 90 horses on the range, 53 were gathered Sept. 16, 17 and 18, 2011. Thirteen were released back to the herd, while the remaining 40 were removed from the range. Twenty-five of those mustangs were made available for adoption at the Montezuma County Fairgrounds following the roundup.

In an effort to provide population control on the range and avoid heavily-debated and expensive helicopter roundups in the future, the BLM instituted a regimen of porcine zona pellucida application for the herd.

An immunocontraceptive agent — in this case, a protein, derived from pig ovaries, that blocks fertilization — PZP has been used on wild horses since the late 1980s and has been proven reliable in reducing pregnancy rates in mares and in overall herd population stabilization.

Since last year’s roundup, 10 Disappointment mares have received an initial dose of PZP, part of the overall management plan for the herd.

“Five mares were given the initial primer at the gather and then they were boostered later,” Borders said. “Five more were given the primer for spring breeding.”

The hope is that the application of PZP will reduce overall herd size and allow for a more natural management than the large gathers.

“We are progressing,” she said. “It is a project that is ongoing and we will continue to administer the PZP and monitor the herd.”

The BLM and the Disappointment Wild Bunch, a local volunteer organization that advocates for the herd, are far from hands off in their approach to the wild horses.

Monitors and volunteers, including TJ Holmes, president of the Colorado chapter of the National Mustang Association, are on the ground almost weekly, observing the horses and taking notes on condition of the horses and the range. The information allows BLM to take preventative measures to ensure the health of the horses and their home.

This year, in particular, concerns were raised over the impacts of drought on the management area. BLM officials were able to take early action to aid the horses, and were helped by much needed rain at opportune moments.

“Earlier in the year, we started to get really concerned about water and feed for the herd,” Borders said. “Fortunately, that area got some good rain in late summer.”

Ahead of the rains, volunteers and officials were able to work on the range, cleaning ditches and ponds, which allowed the landscape to take full advantage of late summer precipitation. Borders said the work, and the rain, has allowed the horses to thrive through the summer and move into the fall and winter months in good health.

“Those horses look really good going into the winter months,” Borders said. “We are thrilled. We feel they will be able to winter very well.”

For more information on the Spring Creek Basin wild mustang herd, visit or