For the past few weeks I've had something digging in my containers at night. The holes are usually about three inches deep and two inches across, but sometimes smaller. I'm not sure what it is, but my dogs just cornered a large opossum in the yard. I was thinking that opossums sometimes dig for grubs, but everything I've read says that's not the case and that opossums are usually good for gardens because they eat slugs and other pests. But that still leaves me not knowing what's digging in my pots!

Whatever it is hasn't done any real damage to any mature plants, but it's dug in a couple of containers with seedlings and will certainly destroy them if I don't put a stop to it. The only other thing I can think of that digs and is nocturnal is an armadillo, but I can't imagine that they'd be able to get into the larger containers. Any ideas?