Squirrels have turned carnivorous and no one knows why

Scientists have described the discovery as "shocking".

Squirrels have always been viewed as a granivorous species, often seen stuffing their cheeks with nuts, seeds or grains.

However, a new discovery, published in the Journal of Ethology, suggests our furry little friends may be opportunistic omnivores with a more flexible diet than previously thought.

A team of scientists from the University of California Davis documented 74 interactions of squirrels with voles from June and July of this year.

What they discovered was that more than 42 per cent of the interactions of ground squirrels of all ages involved active hunting of the small rodents by ground squirrels.

Initially, when undergraduate students showed a video of what they had seen in the field, Dr Jennifer E Smith - an associate professor of biology and the study’s lead author - said she could "barely believe" her eyes.

"From then, we saw that behaviour almost every day. Once we started looking, we saw it everywhere," she said.

"This was shocking. We had never seen this behaviour before.

"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."

The students also found the carnivorous behaviour of the squirrels peaked during the first two weeks of July, linked to an explosion of vole numbers at the local park.

They did not observe the squirrels hunting other mammals, making them suspect the behaviour may have emerged in response to a temporary increase in the availability of prey.

Several mammal species like raccoon, coyote and spotted hyena are known to be “incredible opportunists” showing great flexibility in hunting strategies that help them adapt to human-altered landscapes.

The new findings add squirrels to the list.