Some East Bay ground squirrels have given up eating only seeds and plants and now are choosing to hunt and eat other rodents.
A team of scientists spent 12 years in Briones Regional Park near Martinez studying California ground squirrel behaviors. What they started seeing this past summer startled them.
"Two of my students came to me and said, 'Dr. Smith, we saw these squirrels eating a vole,' and I did not believe them," University of Wisconsin behavioral ecologist Dr. Jenn Smith said.
But the proof was there. The squirrels were faced with an unusually high population of competing rodents: California voles. When the numbers peaked in June and July, the scientists witnessed 74 times when squirrels and voles interacted. More than 40% of the time the squirrels were actively hunting and eating the voles.
"What we noticed is that the squirrels will chase after a vole," Smith said. "They target one animal and they go after it. They grab it by the neck. They have big incisors, and these teeth are very sharp, so never handle the biting end of a squirrel."
Smith said this feeding habit had never been recorded before. She said the behavior may indicate the squirrel is capable of surviving changing environments and future global climate changes.
Smith said there is no reason to be alarmed about squirrels becoming interested in other mammals, adding that they could switch back to solely seeds and plants when vole populations wane.
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"Itās going to be really interesting to see next what happens and whether this influences the squirrel reproductive rates," she said. "As part of a long-term study, we can go back next summer and see where we land."
Smith's team has not seen an increase in size or aggression with the carnivorous squirrels.
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