Kath,
Thanks for the info
I have been covering them when I see them peeking out, but I think I will do a more thorough check. So far I don't think there have been any critters after them - they are far too interested in my apples and quince hanging from the trees to be bothered with digging. A couple of nights ago my (thankfully indoor) cat started going bananas and by seeing where she was looking I was able to see the critter go to the apple tree. I decided to not go out and scare it off...it was a skunk.