‘Opportunistic omnivores!’ Squirrels spotted hunting and eating rodents in ‘shocking’ discovery

Scientists have made a groundbreaking discovery that California ground squirrels actively hunt and eat voles, challenging long-held assumptions about their diet.

The unprecedented findings, published in the Journal of Ethology, reveal that these typically seed and nut-eating creatures are actually opportunistic omnivores.

Researchers at the University of California Davis documented this surprising carnivorous behaviour during June and July 2024, marking the first time such hunting has been observed in the species.

The discovery suggests that squirrels have a more flexible diet than previously thought, with researchers observing numerous instances of hunting, eating and even competing over vole prey.

The study examined 74 interactions between squirrels and voles over the two-month period, with more than 42 per cent involving active hunting behaviour.

The carnivorous activity peaked during the first two weeks of July 2024, coinciding with a surge in the local vole population.

Scientists observed ground squirrels of all ages engaging in this unexpected behaviour at a local park.

The researchers noted that squirrels did not hunt other mammals during the study period.

This selective hunting suggests the behaviour may have emerged specifically in response to the temporary abundance of vole prey in the area.

The findings represent a significant shift in our understanding of ground squirrel behaviour, which had previously been characterised primarily by their consumption of nuts, seeds and grains.

“This was shocking,” said Jennifer E Smith, associate professor of biology and lead author of the study. “We had never seen this behaviour before.”

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“Here’s this never-before-encountered-in-science behaviour that sheds light on the fact that there is so much more to learn about the natural history of the world around us,” she added.

Dr Smith initially struggled to believe the evidence when undergraduate students first presented video footage of the behaviour.

“From then, we saw that behaviour almost every day. Once we started looking, we saw it everywhere,” she explained.

The observations quickly mounted, with researchers documenting numerous cases of squirrels hunting, eating and fighting over vole prey within the brief study period.

The timing of this unusual behaviour appears to be directly linked to an explosion in vole numbers at the local park.

“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, a study co-author.

This adaptability puts squirrels in the company of other opportunistic mammals like raccoons, coyotes and spotted hyenas.

These species are known for their flexible hunting strategies, which help them thrive in human-altered landscapes.

The discovery adds ground squirrels to the growing list of animals showing remarkable adaptability in their feeding habits.

The research team noted that this hunting behaviour was only observed during the summer months, specifically when vole populations were at their peak.

Several key questions remain unanswered following this remarkable discovery.

Researchers are now keen to understand how widespread this hunting behaviour might be among squirrel populations.

Scientists also hope to determine whether and how the behaviour is passed down from parent to offspring.

The study has raised important questions about California’s broader ecology and how this predatory behaviour might impact it.

Of particular concern is the potential for disease transmission between the two species.

“Although we observed no signs of disease in our study population, the behaviours here could influence host-parasite dynamics,” the researchers noted.

The discovery opens new avenues for research into how these traditionally herbivorous animals might be evolving in response to changing environmental conditions.