California squirrels can get a little carnivorous from time to time, according to a recently published study.

Researchers from University of Wisconsin-Eau Claire and the University of California, Davis were the first to observe and document the bushy-tailed rodent species hunting, killing and eating voles, another small rodent species, according to a Wednesday news release.

The study suggests that California ground squirrels, previously thought to solely be granivorous species, are actually an "opportunistic omnivore" with a more flexible diet than previously assumed, which "fundamentally changes our understanding of ground squirrels."

The observations of California ground squirrels engaging in "carnivorous behaviors" were all recorded this year. About 42% of the 74 interactions witnessed between June and July involved "active hunting" of voles.

California ground squirrels deviating from a steady diet of nuts, seeds or grains was "shocking," said Jennifer E. Smith, study lead and associate professor of biology at UW-Eau Claire.

"We had never seen this behavior before. Squirrels are one of the most familiar animals to people. We see them right outside our windows; we interact with them regularly," Smith said. "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."

These creatures are "incredible opportunists," not unlike raccoons, coyotes, spotted hyenas and even humans, who employ similar strategies to help them change and adapt to an ever-changing environment, Sonja Wild, a postdoctoral research fellow in the UC Davis Environmental Science and Policy department, said.

Wild, who leads the long-term California ground squirrels project with Smith, was in disbelief when she heard undergraduate students describe the behavior when they returned from conducting field work. But then she watched the video.

"I could barely believe my eyes," Wild said. "From then, we saw that behavior almost every day. Once we started looking, we saw it everywhere."

California ground squirrels of all ages and genders were seen hunting, eating and competing over vole at a local park between June 10 and July 30, but the "carnivorous behavior" peaked during the first two weeks of July, coinciding with an explosion in vole numbers reported by citizen scientists on iNaturalist.

The tendencies observed emerged "alongside a temporary increase in the availability of prey," according to the study.

"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," Wild said.

Questions about the "carnivorous behavior," ranging from frequency, ecological impact and whether the trait is passed down remain unanswered. But researchers are excited to find out.