DURANGO A mustang advocacy group wants the U.S. Bureau of Land Management to use a contraceptive vaccine to slow helicopter roundups of a wild horse herd in Disappointment Valley north of Dove Creek.
The Colorado chapter of the National Mustang Association points to the efficacy of PZP in curtailing the reproductive rate of mustang mares in other places, including 36,000-acre Little Book Cliffs Wild Horse Range near Grand Junction.
Fertility control has been so successful there that a planned roundup this fall is unnecessary, Jim Dollerschell, rangeland management specialist at the agencys Grand Junction field office, said Friday by telephone.
Inoculating mares from a distance with a PZP-loaded dart started there in 2002 as a research project and continued annually after the research ended in 2007, Dollerschell said.
The number of foals didnt decline until 2004 but since has dropped from 30 to 40 annually to 15 to 20, he said. Only 11 foals were born in 2010.
On many ranges, mustangs natural reproduction rate has increased the number of horses beyond the carrying capacity of the fenced ranges they inhabit.
Dollerschell said that, since they began using PZP, roundups have become fewer and farther between, having taken place in 2002, 2004 and 2007. The roundup scheduled this year was canceled, and one in 2012 may not be necessary, he said.
Little Book Cliffs is home to 135 mustangs, below its capacity of 150, he said.
Mustangs are the free-roaming equines descended from horses brought to the Americas by Spanish adventurers.
The BLM, which oversees mustang herds as part of its charge to preserve an ecological balance on public lands, has used helicopters for years to round up herds for removal to agency holding areas or adoption by the public.
The National Mustang Association doesnt like helicopter roundups because:
Roundups by air stress the horses and cost tens of thousands of dollars. Mustang mares can be injected with PZP via dart from a distance, thus avoiding stress and reducing costs.
Adoption is a good program, but it doesnt match the pace of mustang removals. According to BLM, about 35,000 mustangs are kept in BLM holding facilities.
Young mustangs are most often offered for adoption, thus forever removing the genetics they could have contributed to the herd.
The National Mustang Association instead would turn to PZP and use mineral-baited traps to attract and corral mustangs.
Tom Rice, associate field manager at the Dolores Public Lands Office, said Friday that fertility control would be one of the alternatives to a helicopter roundup.
The Wild and Free-Roaming Horses and Burros Act, approved by Congress in 1971, ordered the protection of the herds as symbols of the pioneer spirit of the West.
Locally, mustangs inhabit Spring Creek Basin, in Disappointment Valley. Advocates say it would offer an ideal place for an annual fertility-control program.
The herd is well-documented by photographs and notes, and most of the horses can be approached to within darting range, advocates say.
The herd will number 90 to 95 horses by the fall roundup, advocates say. If no roundup is held, it will grow to about 130 in 2012. The basin, where the last roundups were held in 2007, 2005 and 2000, can sustain up to about 65 adult mustangs. A roundup is planned for September.
The vaccine known as an immunocontraceptive because it works on the mares immune system is PZP, or porcine zona pellucida, which is derived from pig eggs. Its used around the world to interrupt the reproductive cycle of mammals, including mustang mares.
Dr. Jay Kirkpatrick is director of the Science and Conservation Center in Billings, Mont., where PZP vaccine has been made for 23 years.
The vaccine is used on 43 wild horse herds from California to Maryland, Kirkpatrick said by telephone. Its used on elephants in 13 game parks and on 85 species of zoo animals from Perth (Australia) to Tel Aviv (Israel).
The vaccine is 95 percent effective if done right, Kirkpatrick said.
The Colorado chapter of the National Mustang Association is a representative member of Disappointment Wild Bunch Partners, which also includes Four Corners Back Country Horsemen, Mesa Verde Back Country Horsemen and the San Juan Mountains Association.
In 2007, the Colorado chapter of the National Mustang Association paid for PZP-22, a time-release pellet, which proved nearly ineffective on the five mares released after the roundup. Advocates hope to use native PZP, which is given annually. It doesnt need a roundup to be administered, and it is cheaper than PZP-22, less than $30 per dose. The president of the Colorado chapter of the National Mustang Association was certified to handle and dart with PZP in 2010 in Billings.
Anthony Madrid, wild horse program coordinator for the Carson National Forest in New Mexico, said Tuesday that mustangs have been gathered from the forests 74,000-acre Jicarilla Wild Horse Territory since the late 1970s. The mustang range is about 50 miles east of Bloomfield.
Baited traps, not helicopters, are used to round up mustangs there, Madrid said. Captured mustangs, which are gathered from July until the snow flies, are taken to a holding facility in Farmington.
About 300 mustangs roam the Jicarilla reserve, Madrid said. An appropriate number would be 50 to 105.
We started using PZP a couple of years ago, Madrid said by telephone. Mares we treated have not foaled.
Karen Herman, who adopted five mustangs in 2007 to found the Sky Mountain Wild Horse Sanctuary north of Santa Fe, raises private donations to fund PZP darting of mustangs.
The first use of PZP on forest service land was here, Herman said. We are working to expand humane treatment of mustangs in the wild beyond New Mexico.