Yellowstone bison were driven to extinction in the late 19th century by intensive commercial hunting. (Photo credit: National Park Service/Jacob W. Frank)
Bison in Yellowstone National Park spent more than a century split into two genetically distinct herds. But new evidence suggests they are now moving as a single, interbreeding population.
Herds of wild bison (Bison bison) have existed in Yellowstone's vibrant landscape since prehistoric times. They graze freely across the park's vast grasslands, representing the last remaining free-ranging bison in the United States.
Although these animals are now abundant in the national park, poaching had put the native population at risk of extinction by the early 20th century. Park managers have taken many steps to conserve the Yellowstone bison, including combating poaching and introducing new herds to the region.
Thanks to conservation efforts, both the native herd and the imported group, made up of adults from Montana and Texas and calves from the native Yellowstone herd, were able to survive and thrive. Later genetic studies showed that the descendants of this imported group remain genetically distinct from native bison—to this day.
Over the past 20 years, two subpopulations of Yellowstone bison have merged into one large, interbreeding herd, according to a new genetic study published Sept. 13, 2024, in the Journal of Heredity.
“I think the questions we’re asking about the Yellowstone population can only be answered with genetic technology,” senior study author Jim Derr, a professor at the Texas A&M College of Veterinary Medicine and Biomedical Sciences, told Live Science. “No amount of observational data is going to help, because you don’t know who’s mating with who.”
Genetic studies have shown that two Yellowstone breeding herds have merged into one over the past two decades.
To study the reproductive dynamics of bison in Yellowstone, National Park Service (NPS) staff collected tissue samples from 282 individuals for analysis.
Careful analysis of the bison's genetic markers has provided researchers with clues about their origins and population changes over time.
By comparing genetic markers found in the current Yellowstone bison population with markers from samples collected in the early 2000s, the researchers concluded that the two groups that lived in the area interbred often enough that they were no longer genetically distinct.
The exact reason for these changes remains unclear, but the researchers suggest that it is likely related to
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