Shrinking genetic diversity threatens small herds of buffalo

SANTA FE, N.M. — Evidence is mounting that wild North American bison are gradually shedding their genetic diversity across many of the isolated herds overseen by the U.S. government, weakening future resilience against disease and climate events in the shadow of human encroachment.

The extent of the creeping threat to herds overseen by the Department of Interior — the backbone of wild bison conservation efforts for North America — is coming into sharper focus amid advances in genetic studies.

Preliminary results of a genetic population analysis commissioned by the National Park Service show three small federal herds would almost certainly die off — extinguishing their DNA lineage — within 200 years under current management practices that limit transfers for interbreeding among distant herds.

The study is awaiting peer review by other scientists. It does not include Yellowstone National Park’s herd of some 5,000 unfenced bison, the largest federal conservation herd that’s seen by millions of people who visit the park annually.

“Some of these herds that lost the most genetic diversity do have a high probability of going extinct, due to the accumulation of inbreeding,” explained Cynthia Hartway, a conservation scientist at the bison program with Wildlife Conservation Society who led the analysis.

The preliminary findings were presented at a workshop of the American Bison Society in the buffalo-raising Native American community of Pojoaque, amid impassioned discussions about ensuring the iconic mammal’s lasting place in the wild.

Many of the conservation herds overseen directly by the Interior Department have 400 or fewer animals — leaving them prone to problems of inbreeding and genetic drift that reduce environmental adaptability.

At the same...