UNLABELLED: Dietary flexibility allows animals to respond adaptively to food pulses in the environment. Here we document the novel emergence of widespread hunting of California voles and carnivorous feeding behavior by California ground squirrels. Over two months in the twelfth year of a long-term study on the squirrel population, we document 74 events of juvenile and adult ground squirrels of both sexes depredating, consuming, and/or competing over vole prey. Our video footage, photographic evidence, and direct observations of marked individual squirrels provide insights into the ecological circumstances favoring behavioral flexibility in foraging associated with a decadal peak in vole abundance. Digital video images related to the article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo241126ob01a. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10164-024-00832-6.