I haven't caught anyone at it - which means that the security light, if they set it off, didn't wake me up. My wildlife camera is in NC (not much use in a 2nd floor apartment, admittedly, but I thought I'd be in a house in the woods). So it's up to guesswork: raccoon? possum? squirrel? wood rat? All the above? Somebody chews away at them pretty comprehensively as soon as they fall - and runs off with some of them, too.