Answer: Based on your description it's difficult to make a definite identification of your pest, but it is very possible the culprit is slugs. If the problem is slugs, you will see little slime trails near the plants. (Since slugs work at night, you won't see the slugs themselves.)
Slugs can be controlled by handpicking at night (use barbecue tongs if you are squeamish and drop them into a pail of soapy water), home-made or store-bought beer traps(they fall in and drown), and by using commercial slug poison baits according to label instructions. Be very careful if you use the baits as they can be dangerous to children, pets and wildlife.
Q&A Library Searching Tips