A new study has examined why hunters stopped using one particular location in central Montana known as the Bergstrom site. Although bison remained plentiful in the region, the site was used intermittently for about 700 years before it was eventually abandoned. The findings were published in Frontiers in Conservation Science.

"We found that bison hunters ceased using a kill site in central Montana around 1,100 years ago," said first author Dr. John Wendt, a paleoecologist and assistant professor of rangeland ecosystem management at New Mexico State University. "It appears that hunters stopped using it because severe, recurring droughts reduced the water available for processing animals at a small nearby creek. Site abandonment was a response to environmental stressors and changing social and economic pressures."

Investigating an Ancient Bison Hunting Mystery

To determine what influenced hunting decisions at the Bergstrom site, researchers combined archaeological excavation with environmental analysis. Their work included sediment coring, laboratory testing, climate reconstructions, and studies of past plant and animal activity.

"The Bergstrom site presented a puzzle because it was used intermittently and abandoned when bison were common throughout the region and hunting was intense," Wendt explained. "Why would hunters stop using a site that had worked for so long?"

In spring 2019, the team excavated nine 1×1m test pits at the site. Artifacts and other materials were documented and photographed, while charcoal samples were submitted for radiocarbon dating. Researchers also collected two sediment cores near the excavation area and analyzed them for pollen and charcoal. Additional data on large herbivores and historical climate conditions helped the team evaluate whether environmental changes or other factors contributed to the site's abandonment.

The results ruled out several possible explanations.

"Abandonment wasn't because the site became ecologically unsuitable in any absolute sense. Bison were still around, vegetation hadn't changed, and there was no substantive shift in fire activities," Wendt pointed out. "Bison hunting activity was not simply following prey populations."

Drought and Changing Hunting Strategies

Instead, the evidence pointed to repeated severe droughts that affected the region both before and after the site's final abandonment. These prolonged dry periods reduced water availability and made locations without dependable water sources less attractive for large-scale hunting activities.

At roughly the same time, hunting practices were evolving. Smaller, mobile groups that hunted opportunistically were increasingly being replaced by larger, more coordinated groups. These larger operations often relied on built infrastructure and occupied certain locations for longer periods.

"These larger operations were based on large kills and could produce surplus for trade and winter storage, but they also meant more dependence on specific resources like water, forage for larger herds, and fuel for processing fires," said Wendt.

Because these larger hunting efforts required more resources, suitable locations became harder to find. Ideal sites needed reliable access to water and other necessities, along with landscape features that could help drive and contain bison herds. Cliffs used for bison jumps and natural barriers were particularly valuable. Once such locations were established, they were often used repeatedly for centuries.

Lessons in Climate Adaptation

While larger hunting sites offered advantages, they also increased dependence on favorable conditions. Replacing these specialized locations was difficult, making hunter groups more vulnerable when key resources became scarce.

Researchers believe that long-term success depended on the ability to adapt. Hunting communities passed knowledge across generations and adjusted their strategies as environmental conditions changed. According to the team, that flexibility helped these systems endure periods of climate instability.

The findings may also have relevance today. Modern bison management programs could improve their resilience to changing environmental conditions by maintaining the ability to adjust where and how animals are managed.

The researchers noted that other abandoned bison hunting sites in the region may have been left behind for different reasons. They also emphasized that while the study documents approximately 700 years of use at Bergstrom, it cannot determine how long individual occupation periods lasted or how frequently the site was used during that time. In addition, occasional low-impact use after abandonment may have occurred without leaving evidence that could be detected archaeologically.

"While people have been adapting to the climate for much longer, Bergstrom's abandonment shows that people reorganized in response to recurring droughts in the last 2,000 years," concluded Wendt.