The American bison, once on the brink of extinction, has made a remarkable recovery thanks to conservation efforts, with the Yellowstone National Park population being the sole group of bison in the United States that has continuously existed in the wild. However, recent studies led by researchers from the Texas A&M College of Veterinary Medicine and Biomedical Sciences (VMBS) reveal a significant shift in the genetic structure and breeding behavior of these bison. Their findings, published in the Journal of Heredity, indicate that the Yellowstone bison herd, once considered to consist of two distinct populations, now functions as a single large, interbreeding group. This discovery holds important implications for the long-term conservation and management of these iconic animals.
Historically, Yellowstone’s bison population faced a dire situation, with numbers plummeting drastically during the 19th century. The near extinction of bison in North America due to overhunting and habitat loss is often referred to as the “population bottleneck.” By the early 1900s, fewer than 25 wild bison were known to have survived in Yellowstone, which led conservationists to take drastic measures to ensure the species’ survival. In 1902, bison from western Montana and the Texas Panhandle were introduced to Yellowstone in hopes of creating a stable population. This effort was part of one of the most successful wildlife conservation stories in history, as these bison formed the foundation for the current population.
For many years, researchers and conservationists have debated how best to manage the genetic diversity of Yellowstone’s bison. In fact, a genetic study completed just 20 years ago revealed that the park’s bison population was composed of two separate breeding groups, one found in the park’s summer ranges and the other in its winter ranges. These groups were considered to have maintained their distinct genetic lines. However, the new study conducted by VMBS researchers shows that the bison populations in Yellowstone are now interbreeding, creating a more genetically homogeneous and unified herd.
Dr. James Derr, a professor in the Department of Veterinary Pathobiology at VMBS, emphasized the importance of this new discovery. “This finding certainly has a direct impact on the long-term conservation and management of this iconic bison population,” Derr stated. He explained that understanding the genetic health and breeding behavior of the Yellowstone bison is crucial for ensuring the population’s stability for generations to come.
The researchers’ study involved extensive sampling from various parts of the park, including two major summer breeding groups and two key winter ranges. Historically, these areas were considered to have distinct genetic traits, making them valuable for monitoring genetic diversity. However, the results were clear: there was no significant genetic separation between the summer and winter groups. Instead, the Yellowstone bison population now appears to be functioning as a unified herd with a single, genetically healthy gene pool.
Dr. Sam Stroupe, a postdoctoral researcher at VMBS, further elaborated on the methodology and findings of the study. “To get a clearer picture, we examined samples from the two major summer breeding groups and two major winter ranges,” Stroupe explained. “These are the locations where we would expect to see genetic differences and overlaps. However, the evidence suggests that today’s Yellowstone bison are one large, interbreeding herd.” This insight is vital for conservationists, as it allows them to refine their management strategies to ensure the population remains viable and robust.
Currently, the Yellowstone bison population fluctuates between 4,000 and 6,000 individuals, making it the largest wild bison population in North America. While this number may seem stable, the genetic health of the herd is an ongoing concern, especially considering the historical bottleneck that severely limited the genetic diversity of the species. Prior to this research, the management of the Yellowstone bison population was complicated by the lack of clarity regarding the structure of the herd. Conservationists needed a better understanding of the genetic makeup of the herd to make informed decisions about breeding programs and population management.
With this new information, the researchers recommend that the Yellowstone bison population be managed as a single, interbreeding herd. This will help ensure that genetic diversity remains high, which is critical for the long-term survival of the herd. Genetic diversity is crucial for the health of any species, as it enables populations to adapt to environmental changes and resist diseases. By managing the Yellowstone bison as one large, interconnected population, conservationists can help maintain the genetic diversity necessary to support a thriving and resilient herd.
The study also has broader implications for bison conservation efforts across the United States. Yellowstone’s bison are often seen as a model for other bison populations, and understanding the genetic structure of this iconic herd can help inform conservation practices elsewhere. Additionally, the findings highlight the importance of ongoing research and monitoring in ensuring the survival of species that have experienced population bottlenecks, as these species may require special management strategies to recover fully.
As Yellowstone’s bison population continues to grow and adapt, researchers hope that their findings will provide valuable guidance for future conservation efforts. The goal is to ensure that Yellowstone’s bison, which play a vital role in the ecosystem of the park, continue to thrive for generations to come. Through continued collaboration and research, the bison may one day serve as a symbol of successful wildlife conservation, as they once did in the early 20th century.
Dr. Derr and his team at Texas A&M are optimistic about the future of the Yellowstone bison, thanks to their ongoing research and collaboration with park officials and conservationists. “This study marks an important step forward in understanding the Yellowstone bison,” Derr concluded. “With this new knowledge, we can help guide decisions that ensure the long-term success of this unique and iconic population.”
More information: Sam Stroupe et al, Genetic reassessment of population subdivision in Yellowstone National Park bison, Journal of Heredity (2024). DOI: 10.1093/jhered/esae050