Bison in Yellowstone National Park, previously consisting of genetically distinct and separate herds, have now interbred and become one population, scientists announced this week.
The bison at Yellowstone were still split between two unique herds as of 20 years ago.
Now that is no longer the case, as the herds have bred with each other in the ensuing years and become a single herd of 4,000 to 6,000 individuals, Texas A&M College of Veterinary Medicine and Biomedical Sciences (VMBS) researchers said in a release Tuesday.
“To get a clearer picture, we examined samples from the two major summer breeding groups and two major winter ranges.These are where we would expect to see examples of genetic difference and overlap; however, Yellowstone bison today are clearly one interbreeding herd,” Sam Stroupe, a postdoctoral researcher at VMBS, said.
At one point in the early 20th century, thanks to hunting, the wild population of bison at Yellowstone had dwindled to just 23.
Conservationists at Yellowstone brought in 18 domestic bison females from Montana and a trio of domestic bulls from Texas to form a second population at the park, according to a study published by the VMBS researchers in the Journal of Heredity.
“In one of the greatest wildlife conservation success stories of all time, a small number of domestic bison from western Montana and the Texas Panhandle were introduced in 1902 to existing animals in Yellowstone in the hopes that they would create a stable and thriving population in the world’s first national park,” VMBS professor James Derr said.
Yellowstone is the only place in the U.S. where bison have lived continuously since prehistoric times, according to the National Park Service.
Previously, the possibility of two distinct herds still existing at Yellowstone had prompted activist groups to petition the U.S. Fish & Wildlife Service to extend the bison protection under the Endangered Species Act, arguing that at least one of the distinct populations was under threat of extinction, according to National Parks Traveler.
The groups also argued that, if two populations existed, then the NPS needed to plan and manage a total of 6,000 bison instead of 3,000.
The U.S. FWS, which had previously argued that the bison population was growing and therefore did not need legal protections, was ordered in 2022 to re-examine the petition of the Buffalo Field Campaign and Western Watersheds Project for a third time, according to National Parks Traveler.
The federal agency has not yet made a new ruling on whether the bison should receive Endangered Species Act protections in light of the study.
