Study links Yellowstone bison fate to genetic flaw

A congenital defect combined with U.S. government plans to kill bison exposed to an infectious cattle disease could doom America's last wild herd of pure-bred buffalo at Yellowstone National Park, a genetics expert said in a new study.

The findings were posted on Monday in Nature Precedings, an online archive for pre-publication research by scientists, as the government and environmental groups clashed in court over an icon of Western wildlife that dates to prehistoric times.

Government managers continue to corral hundreds of bison whose search for food has led them to stray from Yellowstone into nearby Montana grazing lands.

Livestock producers fear bison will spread brucellosis, a bacterial infection that can cause domestic cows to miscarry.

A planned slaughter of captive bison that test positive for exposure to brucellosis was placed on hold by the National Park Service last week after conservationists brought a lawsuit challenging the program.

On Monday, the Park Service filed a response reasserting its right to kill as many as 1,600 head of buffalo this year, depending on how the winter progresses.

The agency denied environmentalists' claims that killing brucellosis-exposed buffalo -- 76 are already slated for slaughter -- would irreparably damage the herd.

But the study from Thomas Pringle, a biochemist on the genomic team for the University of California at Santa Cruz, faulted the government as overlooking a hereditary weakness in the bison herd that could be amplified by the culling program.

He found that most Yellowstone bison whose DNA were tested carried a genetic mutation that affects cellular metabolism and makes bison lethargic, rendering them less capable of foraging in deep snow, fending off predators and competing for mates.

Pringle, whose work on other genomes has appeared in professional journals such as Science and Nature, said his bison research demonstrates that culling of the wild herd (see right) based on brucellosis, rather on the health of their genes, may push the species over the edge into a form of extinction.

"They're taking a really high risk of killing bison with healthy genes and getting into a situation where they can't go back; the good DNA will be lost," said Pringle, whose paper relies on published genetic data, analyses of bison fossils and samples from herds at national parks like Yellowstone.

Pringle said he was motivated to release his findings in advance of scientific peer review because Yellowstone bison can't afford the months-long wait while his paper is accepted for formal publication. (Link to current article)

A Yellowstone spokesman said the Park Service was not immediately acquainted with Pringle's study.

Millions of visitors flock to Yellowstone each year to watch wildlife like bison, whose numbers are estimated at 3,700. The West is home to several conservation bison bands, but Yellowstone's are prized as the last wild, pure-bred herds, according to the Park Service. Other conservation herds have DNA contaminated with cattle genes from cross-breeding in the late 19th century, a Park Service report shows.

Hunting west of the Mississippi reduced herds that once numbered in the millions to the fewer than 50 that found refuge in Yellowstone in the early 20th century.

Early conservationists used that small band to save the species, but their efforts predated sequencing of genomes and inadvertently promoted inbreeding, Pringle said.

The founding population for today's wild bison and for commercially bred buffalo possessed the genetic defect that now plagues 72 percent of bison tested at Yellowstone and all those tested at Grand Teton National Park, according to the study.

Buffalo are produced commercially on ranches, like the Montana spreads of billionaire Ted Turner, but those animals are not considered pure-bred because many have cattle genes.

Source:
Reuters, "Study links Yellowstone bison fate to genetic flaw", accessed February 7, 2011
Nature Proceedings, "Widespread Mitochondrial Disease in North American Bison", accessed February 7, 2011