Scientists stunned after observing ‘carnivorous’ squirrels eating voles
Have the squirrels gone nuts?
Killer squirrels might seem like sci-fi, but squirrels in California have been observed hunting and eating voles for the first time, leading scientists to believe that they have a wider diet than once thought. This seemingly species-defying behavior was described in a study published in the Journal Of Ethology.
“We had never seen this behavior before,” exclaimed head author Jennifer E. Smith, an associate professor of biology at UW-Eau Claire, which conducted the study in collaboration with UC Davis.
The striking observations occurred between June and July 2024 during the Long-term Behavioral Ecology of California Ground Squirrels Project at Briones Regional Park in Martinez California.
Of the 74 interactions between ground squirrels and voles observed during that time, 42% involved the nut-crunchers hunting the latter.
This didn’t seem to be an outlier either. Videos and photos showed ground squirrels of all ages and genders hunting, eating and competing over voles during the period.
UC Davis researcher Sonja Wild, a study collaborator who had observed hundreds of squirrels in the field, said she was blown away after her grad students showed her the footage they’d recorded.
“I could barely believe my eyes,” said Wild. “From then, we saw that behavior almost every day. Once we started looking, we saw it everywhere.”
These carnivorous tendencies were especially striking given that squirrels are generally considered granivorous — subsisting on grain.
While some species have been observed supplementing their diet with insects, bird eggs and frogs, this is the first time ground squirrels have been observed preying on voles, suggesting that the species might be more opportunistically omnivorous than previously believed.
“In our twelve years of conducting observations on hundreds of squirrels, we had never observed any incidents of vole hunting before this summer,” Wild told Popular Science. “It is therefore plausible that hunting is innate in these squirrels to an extent.”
Coincidentally, the killing seemed to peak during the first two weeks of July when the vole population skyrocketed.
This indicated that their predatory behavior was prompted by a temporary uptick in the prey species, per scientists, who noted that they didn’t hunt other mammals.
“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,” postulated Wild.
These findings perhaps ultimately prove that there is more to these ubiquitous acorn hoarders than meets the eye.
“Squirrels are one of the most familiar animals to people,” said Smith. “We see them right outside our windows; we interact with them regularly. Yet here’s this never-before-encountered-in-science behavior that sheds light on the fact that there’s so much more to learn about the natural history of the world around us.”
In the future, the team hopes to find out more about the behavior; specifically how widespread vole-hunting is, whether it’s passed down through generations and how it affects ecological processes.
Researchers plan to return to the field next summer to try and gauge what impact the vole predation has had on squirrel reproduction compared to years prior.
