Bison Are Back, But Small Herds Limit Genetic Diversity

The American bison has made a significant comeback, but its genetic diversity remains a concern, according to a new study published in the journal Science. Researchers found that current herds, often small and geographically separated, possess less genetic variety than the bison that once roamed the Great Plains.

The study, conducted by scientists from the University of California and Canada's National Parks, involved analyzing the genomes of 115 historical and 45 modern bison. They concluded that a comprehensive, overarching management strategy for the entire bison population, estimated at 500,000 in the U.S. and Canada, is necessary to promote better gene flow between herds.

The conservation of the American bison is widely considered a success story. After facing near extinction in the 19th century due to rampant hunting, their numbers have rebounded significantly, with thousands of small herds and several larger ones now in existence. However, the recovery has not been without challenges, including opposition from cattle ranchers in prairie states who object to bison grazing in areas where their livestock are excluded.

Most modern bison herds are privately owned and managed on ranches. A smaller population, numbering in the tens of thousands, inhabits public lands and contributes to conservation efforts. These include herds managed by federal agencies in Yellowstone and Theodore Roosevelt National Parks, as well as state-managed herds like the one in Texas. The research also confirmed that historical crossbreeding with other cattle species, a practice employed to prevent extinction, has had a negligible impact on the genetic makeup of contemporary bison.