LOS ANGELES — A UC Davis study has shown a crazy new behavior among California squirrels: They hunt like carnivores, shooting down and then consuming other, smaller rodents.

As part of an ongoing 12-year study of California ground squirrels in Briones Regional Park in Contra Costa County, researchers last summer observed squirrels beginning to hunt and eat voles, a cousin of field mice.

This suggests that squirrels are much more opportunistic in their feeding than previously thought, wrote the authors of the study, published Wednesday in the Journal of Ethology. Squirrels typically eat acorns, seeds, nuts, and fruits, but they have been known to occasionally eat fresh carrion or roadkill, insects, eggs, or other discarded foods. Some squirrels on California college campuses have become infamous among students for their demanding behavior, even going so far as to win student elections, but they have never been seen hunting smaller rodents on such a scale.

“It was shocking,” said lead author Jennifer E. Smith, an associate professor of biology at the University of Wisconsin-Eau Claire. “We have never seen this behavior before. Squirrels are one of the most familiar animals to humans. We see them right outside our windows; we interact with them regularly. Yet here is this behavior never before seen in science that highlights the fact that there is so much more to learn about the natural history of the world around us.

A video released by researchers shows a ground squirrel grabbing a vole by the neck and shaking it back and forth — a clear predatory behavior intended to quickly kill prey, said Dan Blumstein, a professor of ecology and evolutionary biology at UCLA studying groundhogs, a related study. species of large ground squirrel. In squirrels, most biological dietary factors, such as their teeth and stomachs, are adapted to vegetation like nuts and seeds, not meat, he explained.

Blumstein, before reading the details of the study, thought that carnivorous behavior might have been limited to female squirrels desperate for the nutrients needed to feed their young. But according to the study, this behavior was seen in male and female squirrels of all age groups. They displayed other behaviors typically associated with predators: when one squirrel successfully stalked prey, another squirrel would sometimes try to steal it from the hunter.

“I could hardly believe my eyes,” said Sonja Wild, a postdoctoral researcher at UC Davis who co-led the project alongside Smith. “From that point on, we saw this behavior almost every day. Once we started looking, we saw it everywhere.

The study authors posited a theory about this novel squirrel behavior: a boom in the local vole population – tracked by the crowdsourcing website iNaturalist – could have led the squirrels to take advantage of an available prey source.

“The fact that California ground squirrels are behaviorally flexible and can respond to changes in food availability could help them persist in environments that change rapidly due to human presence,” Wild said.

Alice Morris, a University of Idaho graduate student who studies Idaho’s endangered ground squirrel population, said she has never seen this type of behavior in her observations and is surprised by the results of the study. Her friends and family texted her about it several times on Wednesday, she said.

Rising temperatures due to climate change can disrupt ecological food chains, according to the National Wildlife Federation. A lack of suitable vegetation could cause smaller species to disappear, leaving larger predators to wander into unfamiliar habitats in search of reliable food sources.

“Squirrels are great examples of how animals can adapt to changing conditions,” Morris said.