California ground squirrels, typically known for their nut-loving habits, have been observed hunting and consuming voles, challenging the long-held belief that they are strictly herbivores. This surprising discovery, documented by researchers from the University of Wisconsin-Eau Claire (UW-Eau Claire) and the University of California (UC), Davis, reveals a previously unknown carnivorous side to these common rodents.
This groundbreaking observation stems from the Long-term Behavioral Ecology of California Ground Squirrels Project, led by Jennifer E. Smith of UW-Eau Claire and Sonja Wild of UC Davis. During the summer of 2024, the project’s 12th year, researchers witnessed ground squirrels actively hunting voles in a remarkable 42% of their interactions with the smaller rodents. This unexpected behavior, observed at Briones Regional Park in Contra Costa County, peaked in early July, coinciding with a surge in the vole population.
A California vole.
“We had never seen this behavior before,” Smith stated in a UC Davis release. The ubiquity of squirrels, often seen just outside our windows, makes this discovery even more astonishing. This previously undocumented behavior underscores how much we still have to learn about even the most familiar animals.
Wild, also surprised by the findings, recounted, “I could barely believe my eyes. From then, we saw that behavior almost every day. Once we started looking, we saw it everywhere.” The research team, including undergraduate students, meticulously documented instances of ground squirrels hunting, consuming, and even competing over voles.
The study, published in the Journal of Ethology, proposes that the increased vole population may have triggered the squirrels’ hunting behavior. This suggests that California ground squirrels, previously classified as granivores (grain eaters), might actually be opportunistic omnivores.
This dietary flexibility could be crucial for their survival in environments increasingly impacted by human activity. Wild explained, “The fact that California ground squirrels are behaviorally flexible and can respond to changes in food availability might help them persist in environments rapidly changing due to the presence of humans.”
California ground squirrels
Smith emphasized the importance of fieldwork, stating, “Through this collaboration and the data coming in, we’re able to document this widespread behavior that we had no idea was going on. Digital technology can inform the science, but there’s no replacement for going out there and witnessing the behavior because what animals are doing always surprises us.”
While the study raises new questions about the prevalence of this behavior, its transmission across generations, and its ecological impact, it undeniably reshapes our understanding of these common creatures. This discovery highlights the dynamic nature of wildlife and the ongoing need for research, even on seemingly well-known species.
The researchers are continuing their investigation to answer these remaining questions and gain a deeper understanding of this newly observed carnivorous behavior. This surprising discovery underscores the complexity of animal behavior and the importance of continued observation and research, even for familiar species like the California ground squirrel.
