A new water catchment system and birth-control dart program have stabilized the Spring Creek Basin wild horse herd in Disappointment Valley.
Today, a manageable 62 wild mustangs roam the 22,000-acre swath of BLM land southwest of Norwood, down from 119 horses in 2007.
“We’re keeping the horse population in balance with what the range can support,” said TJ Holmes, a BLM volunteer who helps manage the herd. “The herd is healthier, and so is the range, with grasses coming on strong and a variety of vegetation.”
The key to controlling the wild horse population is administering a contraceptive called Porcine Zona Pellucide (PZP) to certain mares each season, starting every March.
Dosages have been delivered via dart gun by Holmes and BLM staff to selected mares in order to reduce birth rates in a way that supports genetic diversity.
“Our objective is to treat 17 mares this year,” said Mike Jensen, range specialist for the BLM’s Tres Rios district.
Since it began in 2012, the PZP program has effectively controlled the Spring Creek horse population and prevented roundups.
In 2011, before the fertility controls were in place, 14 foals were born to the herd. After treatment, the number of foals dropped to eight in 2013, seven in 2014, and just two foals in 2015.
Holmes reported that in 2016 four fouls were born and four adult horses disappeared and are presumed dead.
The contraceptive method has become the preferred strategy to manage wild horse populations, which can quickly get out of control if left alone.
When populations outstrip range and water sources, roundups are required, which are problematic because the horses must be housed for long periods in BLM corrals.
In 2007, a controversial roundup that used a helicopter to drive Spring Creek Basin horses into pens triggered outcry from horse advocates because of the stress it puts on the animals.
The BLM is preparing an environmental assessment on using less disruptive bait-trapping method for roundups if they are needed to cull the herd.
“It is easier and safer on the horses than being chased by helicopters,” Holmes said. “When managing wild animals, slower is better.”
Bait trapping also enables managers to choose which horses to roundup in a way that is best for the herd, specific bands, and genetic diversity, she said.
Tank of water
The Spring Creek Basin Herd management area is a high desert landscape with limited water. To improve and spread out resources, ponds were installed as well as two water catchment systems utilizing tanks donated by an oil-and-gas company.
Last fall a water tank on the southern end of the range was improved in partnership with the BLM and volunteers from the “Wild Bunch,” made up of the Colorado chapter of the National Mustang Association, Four Corners Backcountry Horsemen, and Mesa Verde Backcountry Horsemen.
A giant plastic apron and piping were installed to funnel natural precipitation into the tank and trough for the horses.
“It is full of water and functioning,” Jensen said.
The water source is now more reliable and allows horses to forage that area while promoting even grazing across the range, Holmes added.
In 2015, the BLM canceled a cattle grazing allotment that overlapped the Spring Creek wild horse management area reducing forage competition for horses.
Jensen said in the future, range scientists will asses the ecological conditions and carrying capacity to determine whether or not the appropriate management level of horses can be increased.
In March, students from the University of Missouri will spend their spring break on fence reconstruction efforts on the east boundary of the Spring Creek Basin management area. Pack mules from the U.S. Forest Service will deliver the fencing materials to the remote worksite.
“The herd is on an even keel right now thanks to the great BLM partnerships. We are so grateful for good management of these horses,” said Holmes, who was featured in a Feb. 7 article on the Spring Creek Basin herd by National Geographic. “Our goal is to keep wild horse wild and do everything we can to keep them out of pens.”
The Spring Creek Basin herd and management area is designated and protected under the federal Wild Free-Roaming Horses and Burros Act of 1971. Bays, sorrels, grays, and pintos can all be found in the Spring Creek Basin herd. The horses are generally around 14 hands (56 inches) in height and weigh 700-800 pounds.