Over 18 observation days, researchers witnessed squirrels hunting voles 31 times, with 17 confirmed kills

It's easy to assume that the only thing a cute little squirrel poses a threat to is a nut, but it turns out they could have more of a murderous streak than we realized. After watching squirrels in California for 12 years, a team of scientists has seen them actively hunt down and kill small rodents this past summer.

California ground squirrels are known to mostly eat acorns, seeds, nuts and fruit, sometimes supplementing their diet with insects and bird eggs. Evidence of them eating the occasional meal of meat has been found too, but it wasn't clear whether they were just opportunistically scavenging dead animals or actively hunting them.

Now, we have very clear photo and video evidence (below) that it's the latter. The Long-term Behavioral Ecology of California Ground Squirrels Project has been monitoring the animals in Briones Regional Park every summer since 2013 - and this year, some startling new behavior emerged.

Over 18 observational days in June and July 2024, the researchers observed dozens of instances of ground squirrels actively hunting and/or preying upon smaller rodents called California voles. It wasn't just one psycho squirrel going rogue either - males and females, adults and juveniles all participated.

Out of 74 observed interactions between the two species, 31 involved the squirrels actively hunting the voles. Most of the time, the squirrels seized an opportunity to chase a vole across a short distance in an open area, while a few stalked and quietly ambushed their prey. Out of the 31 hunting attempts witnessed, 17 ended in a successful kill, usually done with a few quick bites to the neck.

In 70% of cases where the squirrel won, they were seen carrying the dead vole somewhere else to eat it. They always started by removing the head, then either pulled meat out of its torso or stripped off the fur before chowing down.

"This was shocking," said Jennifer Smith, co-lead author of the study. "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. 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."

So if the team has been watching squirrels closely for over a decade, why hasn't this behavior been seen before? It seems that this year, the vole populations in the area and elsewhere in California absolutely exploded, and the ever-adaptable squirrels were likely just exploiting the plentiful new food source. After all, none of the squirrels was ever seen hunting any other mammals during the observation period, the team says.

"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," said Sonja Wild, co-lead author of the study.

The researchers say they're looking forward to next year's observation period to see if this hunting behavior happens again, whether it can be passed down between generations, and what impact if any it has on squirrel reproduction compared to previous years.

The research was published in the Journal of Ethology. You can see clips of the squirrels hunting voles in the video below.