Scientists classify California ground squirrels as granivores because they eat mostly acorns and seeds. However, they have been observed eating bark, flowers, leaves, and the occasional insect or bird egg.
Biology professor Jennifer Smith has studied California ground squirrels for many years. In 2024, her students saw something that shocked her. They saw one of the squirrels chase, kill, and eat a vole. A vole is a mouse-sized rodent common across the western coast of North America.
Jennifer was very surprised to see a ground squirrel hunting a vole, also a granivore rodent. “I couldn’t believe it. In twelve years of studying these ground squirrels, we have never seen anything like this before!” she said.
Jennifer’s team documented 74 cases of squirrels hunting voles in Briones Regional Park in California. Their findings have now been published in a study.
From a population of 125 squirrels, they recorded at least 27 individuals hunting voles. The squirrels stalked, chased, and pounced on their prey. The squirrels were surprisingly good hunters, succeeding in 55% of hunting attempts .
“The sounds on the videos were quite shocking as the squirrels crunched on the skulls of the vole prey!” Jennifer said.
Jennifer and her team want to know if eating voles helps squirrels better survive over winter, when plant materials may be scarce, or if it changes the number of squirrel babies born.
The discovery that squirrels hunt voles changes how scientists understand California ground squirrels. These squirrels are now considered omnivores, animals that eat plants and animals, rather than granivores.
David Brown adapted this story for Mongabay Kids. It is based on an article by Shanna Hanbury published on Mongabay News.
