Squirrels feeding on voles—small rodents—instead of their usual diet of nuts, acorns, seeds, or other plant-based foods was unheard of until recently. This surprising behavior was observed in California’s Bay Area and documented for the first time by researchers from the University of Wisconsin–Eau Claire and the University of California. Their findings, published in the Journal of Ethology, challenge the traditional classification of squirrels as granivores, primarily reliant on seeds, grains, and nuts, and instead reveal them as opportunistic omnivores with a more adaptable diet that includes meat.
The first sightings of carnivorous behavior in ground squirrels occurred in 2024 during the 12th year of the Long-term Behavioral Ecology of California Ground Squirrels Project, conducted at Briones Regional Park in Contra Costa County. Of 74 squirrel interactions observed between June and July, nearly half (47%) involved hunting voles as prey.
“This behavior is completely unexpected in squirrels, some of the most familiar animals to humans,” said Jennifer E. Smith, lead author of the study and associate professor of biology at UW–Eau Claire. Smith co-leads the research with Sonja Wild from UC Davis. “This discovery highlights just how much we still have to learn about this species and the natural world around us.”
Researchers documented the squirrels’ opportunistic hunting behaviors through videos, photographs, and direct observations. These behaviors, displayed by squirrels of all ages and sexes, included chasing, feeding on, and competing for vole prey. The activity peaked during the first two weeks of July, coinciding with an explosion in the vole population, as reported by citizen scientists using iNaturalist.
