Sometimes if they cannot find small rodents, and they are hungry. They are omnivorous, eating both meat and fruit. Song of Songs 2:15 and Aesop's fable "The Fox And The Grapes" both attest to this fact. Song of Songs is a biblical love poem while Aesop's fable is an allegorical snippet.
I do not know about grapes but they have eaten most of my tomatoes this year!
Only in fairy tales