Yellowstone National Park is home to the only group of American bison that has continuously existed as wildlife since the late 19th century. These bison once faced near extinction due to poaching, with only 23 individuals remaining by the early 1900s. To help restore the population, 18 females from Montana and three bulls from Texas were introduced to Yellowstone. Over time, the population grew, but genetic studies revealed that the bison in the park were split into two distinct subgroups. However, a new study has revealed that these two groups are no longer genetically separate, and instead, the bison population now functions as one interbreeding herd.

The research, published in the Journal of Heredity, shows that the bison in Yellowstone have become more genetically connected than previously thought. There were signs of separate breeding groups in past studies, but the latest analysis found no significant genetic differences between the groups. The researchers from Texas A&M College of Veterinary Medicine and Biomedical Sciences used advanced genetic tools to study the bison’s population structure by looking at both summer breeding groups and winter ranges. Their findings indicate that the bison now breed freely across the park, making the entire population genetically healthy and united.

Historically, Yellowstone’s bison population faced a severe crisis, often called a “population bottleneck,” where numbers dropped drastically due to hunting and poaching. By the early 1900s, the remaining wild bison were rescued and given the chance to recover. Since then, their numbers have fluctuated between 4,000 and 6,000 individuals, forming one of history’s most successful wildlife conservation stories.

This discovery is important for conservation efforts, as it provides more precise insight into the genetic health of the bison population. With this information, Yellowstone bison can be managed more effectively to ensure the long-term stability of this iconic species. Researchers hope that understanding the current breeding patterns will help maintain a healthy, sustainable bison population in the park for generations.

References

• Stroupe, S., Geremia, C., Wallen, R. L., White, P. J., & Derr, J. N. (2025). Genetic reassessment of population subdivision in Yellowstone National Park bison. Journal of Heredity, 116(1), 1–9. https://doi.org/10.1093/jhered/esae050
• Price, C. & Texas A&M University. (2025, March 5). After 120 years of conservation efforts, Yellowstone bison are a single breeding population, researchers discover. Phys.Org; Texas A&M University. https://phys.org/news/2025-03-years-efforts-yellowstone-bison-population.html