Squirrel Nuissance problem!

[orchidjunky]

Some of my plants have been dug up by stupid squirrels that are around my complex. They mostly dig into my potted soil plants, however they have now decided to dig in the orchids bark too!!! I was wondering what is a good deterrant for this behaviour? I've read that squirrel repellants are not that effective and that cayenne pepper/hot sauce works but needs to be constantly reapplied... I'm thinking about putting rocks on the tops of the soil/bark to prevent the behavior but I don't know if this will be bad for the plants or will the squirrels just pull the rocks off...

I have an aloe vera, rosemary plant, crown of thorns and some cattleyas that seem to be the main targets... would putting rocks on top of these hurt the plants?