Wild Horse Study: Smaller herd suffering genetic harm

In a study recently reported in the Daily Advance, a Texas A&M professor advises that adding horses would reduce inbreeding. See article below:


By JOHN HENDERSON
Staff Writer

Monday, May 05, 2008

The wild horse herd in Corolla has suffered genetic harm as the result of a Currituck County-endorsed program limiting its size, a study has concluded.

Inbreeding among the horses is the culprit, and could lead to defects, according to a study released by Texas A&M professor Gus Cothran, an equine geneticist who is a worldwide expert on feral herds.

A new study by a Texas A&M University professor suggests that the smaller size of the herd of wild horses on Currituck County Outer Banks is hurting its genetic diversity.

DNA testing taken of the herd of 89 showed "low genetic diversity" due to the inbreeding among the small herd, Cothran said. The horses have not yet shown outward physical signs of deformities, but that will become a possibility if the herd numbers aren't increased, he said.

"There certainly are 20,000 known genetic defects in humans," Cothran said. "Any one of those is a possibility" in the horses.

Examples could include clubbed feet or dwarfism, he said.

To prevent any further genetic decline, Cothran is recommending that the herd be allowed to reproduce and grow in number, and a few new horses be injected into the mix.

Cothran's study is recommending a herd in excess of 110 to increase genetic diversity. But that would conflict with an agreement to limit the herd to 60 that was agreed to in 1999 by Currituck County, the National Wildlife Refuge, and the herd's overseers, the Corolla Wild Horse Fund.

Federal officials have been concerned that too large of a herd could damage the habitat at the Currituck National Wildlife Refuge. The refuge makes up a large portion of the horses' grazing area on the Currituck Outer Banks north of Corolla.

Refuge manager Mike Hoff could not be reached for comment on Friday.

Karen McCalpin, the director of the Corolla Wild Horse fund, said the group is trying to be pro-active before the horses start to show outward physical genetic deformities.

"Low genetic diversity (in the horse's DNA samples) means it is starting to be a problem, that already irreparable genetic harm has occurred (to the horses)," she said. "We're recommending ways to prevent further harm, to have a larger herd."

The horses are believed to be descendents of Spanish mustangs that arrived several hundred years ago, and are considered a tourism draw for Currituck County.

A few years ago, the herd numbered 119. But in the past year, an aggressive adoption effort and a birth-control program have reduced its size to 89.

"We've physically removed horses. We adopted out 30 horses in the last 18 months," McCalpin said.

In the wake of Cothran's study, the horse fund has requested a moratorium on the removal of horses. The birth control program would remain in effect, however.

"In the meantime, we are trying to gather scientific data that all of us need to make a management plan that will be in best interest of the wild horses," McCalpin said.

The U.S. Fish and Wildlife Service and Estuarine Research Reserve will be conducting a study to determine exactly where the horses are feeding and what impact they are having on the wildlife refuge.

"The 'impact and carrying capacity study' will give us a lot of important data we don't have, not just about horses, but the impact of feral hogs, what kinds of vegetation are being eaten by which animal," McCalpin said.

She said the information could help define what areas should be a horse sanctuary.

"The ultimate goal is to be able to own that land," McCalpin said. "That will help me when I go to a foundation to ask for support to purchase land."