My friend in Mystic, CT, lived in town on a well-settled street. Had a cat flap which her cats used daily and nightly. For some mysterious reason she noticed they were suddenly eating a lot of dry cat food, esp. at night when she was asleep. She'd get up in the morning and find they'd been in the cupboard and made a mess whilst helping themselves.

Well, that's what she thought until one night she happened to get up, heard rustling in the kitchen and looked through to see a raccoon happily pillaging the cat food bag. Not only that, when she turned the light on, it made a beeline for the "raccoon flap" exiting the house. No more unlocked cat flap at night after that!