UNIVERSITY PARK, Pa. – It’s a long way – in terms of miles, habitat and species - from domesticated ponies in the verdant meadows of central Pennsylvania to wild mustangs in the parched high deserts of Arizona, California, Nevada, New Mexico and Wyoming, but research under way in Penn State’s College of Agricultural Sciences is bringing them closer together.
Researchers hope that contraception methods that seem to work in a small herd of ponies kept in a lush, partially wooded pasture at the Penn State Horse Farm not far from Beaver Stadium can be applied to hundreds of thousands of wild horses out West where overpopulation is straining habitats and wildlife management budgets.
“A pony is considered to be any horse that is less than 14.2 hands (58 inches) high,” explained Nancy Diehl, assistant professor of equine science.
“Actually, ponies are a lot closer in size to the mustangs than the 1,2OO-pound quarter horses we have at Penn State. It makes sense to do our research with ponies. We currently have a herd of 14 ponies – 13 mares and a stallion.”
Most contraception work with wildlife – and that is what the wild horses of the West are considered – has been done using vaccines, according to Diehl.
Teaming up. Penn State professor Gary Killian, who has done extensive contraception research with white-tailed deer, has teamed on the pony project with Diehl, whose expertise is horse behavior.
“We are inserting intrauterine devices very similar to the ones that prove so effective in preventing human pregnancies,” said Diehl, who is a veterinarian.
“We are trying this new approach because the vaccines only seem to prevent pregnancies for a year or so. This appears to be a longer-lasting, more effective method of dealing with wild horse overpopulation in the West.”
Federal law. Under federal law, wild horses are managed differently than any other wild mammals whose numbers become a problem.
The Wild Free-Roaming Horses and Burros Act of 1971, as amended in 1976, prohibits the killing or slaughter of any wild horses or burros.
They can be collected for adoption by private citizens – and thousands annually are – but that program is limited by the difficulty and unpredictability of the taming process.
“The reality is that not nearly enough wild horses are adopted to control the wild populations, and many western states now collect thousands of the animals and keep them in holding facilities that are humane, but crowded and demoralizing to the captive horses,” said Diehl, who journeyed to the Reno, Nev., area last year to assess the situation firsthand.
“From a behavioral standpoint, the holding facilities are disasters for the horses they hold. The states are doing the best they can, but the horses collected can never be released back into the wild, and most are there for as long as they live.”
Promising. The IUD approach is promising, but Diehl and Killian know that inserting them in wild horses won’t be as easy as with domestic ponies.
“The ponies are docile and just stand there,” said Diehl. “With the wild mustangs, they would have to be inserted as part of a program that involves capturing and administering anesthesia to take blood samples.
“We are working with the state wildlife agency in Nevada, and Killian went to the West and inserted IUDs in 15 captured mustangs last year.”
They are presently being monitored. Officials in the state agencies seem to be encouraged by methods the team is developing.
The team is working closely with Nevada’s state veterinarian and researchers at the National Wildlife Research Center in Fort Collins, Colo., who are collaborating in the study.
Cause for alarm. Wild horses are reproducing at an alarming rate. Wildlife management officials are concerned because the herds have been increasing by 15 to 20 percent per year, doubling their population every four years.
Before the federal protection was passed, wild horses were victims of ruthless and indiscriminate slaughter for commercial purposes and their numbers plununeted.
Although horses evolved in North America, no one is sure why they didn’t exist on this continent at the time of European exploration.
Spanish explorers reintroduced horses to North America beginning in the late 15th century, and Native Americans helped spread horses throughout the Great Plains and the West.
Until as recently as the mid-20th century, horses continued to be released onto public lands by the U.S. cavalry, farmers, ranchers and miners.
Not enough. For Diehl, it won’t be enough to learn that the IUDs just prevent pregnancy. She must becertain they don’t wreck the wild horses’ social structure.
“There are many questions to be answered,” she said.
“We want to know that they stay in and work under natural breeding conditions. We need to know that they are safe for the horses.
“We are monitoring the ponies really closely, and the IUDs so far are preventing pregnancies. We won’t be able to do that with the wild mustangs.
“But we also want to be sure they won’t effect their normal behavior,” she added.
“Wild horses have a very important social structure that is made up of small groups consisting of a stallion and a harem of mares. We want to see the affects of mares not getting pregnant. There no doubt will be more wear and tear on the stallions. We will be monitoring their behavior as well as their physiology.
“We must be sure not to alter the harem structure, because if we change the harem structure, we change wild horses as we know them.”
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