Researchers have found a population of California ground squirrels in an East Bay park that are actively hunting and eating voles, a behavior that has shocked squirrel experts.

We all think of squirrels as pretty cute and harmless — the most acceptable of the rodents, really. Their bouncy tails and adorable way of eating acorns have endeared them to many humans who haven't had to remove a squirrel nest from their attic.

But squirrels don't eat just acorns. Scientists have long considered squirrels omniverous, but their typical diets outside of nuts and seeds are usually opportunistic — they'll steal an egg out of a nest, eat a small bird, feast on the carcass of a rodent, or chow on an insect if one presents itself.

UC Davis researchers have now found California ground squirrels doing something they weren't thought to be capable of, which is actively hunting and preying on smaller mammals, namely voles.

In a study published in the Journal of Ethology, researchers say they observed squirrels hunting and eating voles in Briones Regional Park. Out of 74 interactions they recorded between squirrels and voles, 42% involved predation, the researchers say.

"Once we started looking, we saw it everywhere,” said UC Davis researcher Sonja Wild, in an announcement about the study, per KRON4. “We saw that behavior almost every day."

Wild posted video of some of this behavior — and if you're not the National Geographic-watching type and get upset by animal-on-animal violence, don't press play.

The squirrels were also observed, in at least eight instances, competing with other squirrels over vole prey, or trying to steal a vole carcass from another squirrel.

The researchers believe that this predatory behavior, which they called "shocking" to observe, has coincided with a sudden abundance of voles in this part of Contra Costa County.

"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 in the announcement.

"Squirrels are one of the most familiar animals to people,” says Jennifer E. Smith, lead author of the study an associate professor of biology at University of Wisconsin-Eau Claire. “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."

Interestingly, the squirrels were not seen preying on any other mammals besides voles.

So, head on out to Briones Regional Park if you want to see some of this carnivorous squirrel action.

Photo via Sonja Wild/UC Davis