On a cold, sunny day on the treeless plains of north-central Montana, hunters close in on their prey. Several bison and their calves watch nervously as a pickup truck slowly circles them, a rifle pointed out of the passenger window. A shot rings out, and a few minutes later, a young bison calf plops down on the ground, grunting and squirming. The hunting party—a team of biologists—moves in, warily eyeing the larger bison, eager to get a blood sample and move away from the agitated creatures. Once they fill a giant plastic syringe, they give the calf a shot, and it stands up on wobbly legs and staggers back to the herd.

Welcome to the American Prairie Foundation preserve, the front lines of the efforts to save America’s bison and restore a large swath of the North American Great Plains. The bison is often heralded as the nation’s first and greatest conservation victory—in the last century the population grew from fewer than 1,000 to half a million—but the story is not that simple.

In the late 1990s, James Derr, a geneticist at Texas A&M, discovered that most of the roughly 500,000 bison in North America have a tiny amount of cattle DNA mixed into their genome—the consequence of ranchers crossbreeding bison and cattle a century ago. The revelation that all but 10,000 bison are hybrids shook the conservation community. In 2004, the American Prairie Foundation learned that their bison, which today number 45, are among the few that are pure. Others haven’t been as lucky. When Derr’s discovery came to light, scientists realized that conservation efforts then underway wouldn’t ensure the survival of genetically pure bison. Extinction is still a threat. Now conservationists like those in Montana are hunting bison in a benign but urgent sense because saving them goes hand in hand with saving the prairie, the world’s least protected terrestrial ecosystem. So while the species was almost decimated by the Great Hunt, their survival depends on this Next Great Hunt. 

Curt Freese, a researcher who has studied bison genetics, is head of the World Wildlife Fund’s Northern Great Plains Program. Freese was instrumental in setting up the Foundation’s preserve. Though the long-term consequences of hybridization are unknown, he says, “if you have a chance to maintain them as pure, it makes sense. Once the genes are in there, there’s no getting them out.”

Scientists say that only the purest bison—those most similar to the ones that made up the massive, rambling herds of yesterday—should be used to repopulate the Plains. (Though biologists are reluctant to use the word pure because genetic markers might be present at levels current technology can’t detect, today’s tests find some bison to have no cattle genes.) Maintaining the bison’s genetic purity will help ensure the survival of the species and pave the way for the animals to reassume their historical ecological role. These herds are critical to rehabilitating large, landscape-scale prairie habitat because other species rely on their grazing for survival. Cattle genes, which make up less than one percent of the genome of most affected bison herds, could influence a multitude of traits, including the bison’s ability to resist disease, withstand cold weather, and migrate. The truth is no one knows what the effects of hybridization will be. But when it comes to the future of the bison, no one wants to be surprised.

Posted on Jan 3, 2008 at 8:30 AM
Permalink | Comments (0) | TrackBacks (0)