Cuties on the hunt: How California’s squirrels have turned carnivorous

Squirrels may seem like harmless, nut-hoarding furballs, but some have a surprisingly ruthless side—preying on, tearing apart, and devouring voles.

This startling behaviour is the focus of a new study published Wednesday in the Journal of Ethology, marking the first documented evidence of widespread carnivorous tendencies in these seemingly innocent animals.

“There is always something new to learn, and wild animals continue to surprise us,” lead author Jennifer E Smith, an associate professor of biology at the University of Wisconsin-Eau Claire said in an interview with AFP.

So, why are squirrels in California turning to such bloodthirsty behaviour? How did scientists uncover this shocking reality? Here’s a closer look.

A startling discovery

Smith and her colleagues made their discovery during the 12th year of a long-term study conducted at Briones Regional Park in Contra Costa County, California.

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Each June and July, the research team live-traps, marks, tags, and releases ground squirrels, enabling them to be individually identified and tracked.

Co-author Sonja Wild, a postdoctoral researcher at the University of California, Davis, recalled how she was sceptical when undergraduate students came in from fieldwork and narrated the account of a flesh-eating squirrel.

“No, I’m not sure what you’re referring to,” she said. Then she watched the video.

“I could barely believe my eyes,” said Wild. But “once we started looking, we saw it everywhere."

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Over the course of 18 days in the summer of 2024, the team recorded 74 interactions involving ground squirrels and voles. In at least 42 per cent of these cases, the squirrels actively hunted their rodent prey.

The team noted that adults and juveniles, both male and female, hunted the voles, and usually acted alone. Occasionally, squirrels were seen trying to steal dead voles from one another.

“In a changing world with many technological advances, there is no replacement for direct observation of natural history, including watching the squirrels and birds that often visit our backyards,” Smith told AFP.

Oppurtunistic omnivores

The study’s findings suggest that squirrels might be more accurately described as ‘opportunistic omnivores,’ given their readiness to hunt and consume live prey, especially when prey is abundant

John Koprowski, dean of the Haub School of Environment and Natural Resources at the University of Wyoming, who was not involved in the research, explained to CNN that protein is a crucial yet limited resource for squirrels. Hunting voles, he noted, likely provides a quicker and more accessible source of nutrition compared to seeds.

“It’s a wonderful way for them to capitalise on a very abundant resource … to provide enough sustenance for many (squirrels) to use,” Koprowski said.

The researchers observed that the squirrels’ surprising behaviour coincided with an unusual population boom of California voles in July. The cause of this sudden explosion in vole numbers remains unclear.

“The super abundance of voles during this particular summer really opened up the novel dietary niche for them,” Smith told The Guardian.

Smith added that this dietary flexibility could help squirrels adapt to challenges like climate change and human presence.

“This is important because they are a major prey source for California ecosystems, and they are a native species,” she said. “If they’re doing well, it creates more opportunities for other species, especially those threatened, to survive and thrive.”

During their observations, researchers documented squirrels crouching low to the ground before ambushing their prey. However, more often, the squirrels chased voles, pounced on them, delivered a neck bite, and followed up with vigorous shaking.

Looking ahead, scientists plan to explore how widespread this hunting behaviour is across different squirrel species, whether it is learned from parents, and how it influences broader ecosystems.

“Animals can either adapt or go extinct in a human-impacted world,” Smith told CNN. “These animals are showing us the incredible resilience of some species, and by studying these processes, we can offer meaningful insights for conservation.”

With input from agencies