If no sign of raised mound, soil-surface tunnels then it is voles and moles aren't plant eaters anyway. There are all sorts of commercial organic products available for controlling both.

Dave

A gopher finished off one of my plants yesterday, plant just sunk down in the hole. I put the hose down the hole and flushed him out. My Corgi was chasing him when I went in the house, not wanting to see her kill him. I've never had a gopher bother the tomatoe plants before. Good luck with whatever is getting yours.

We have Ground Squirrels...nothing has worked with them. Have trapped, used pellet gun, flooded their holes (one goes under our house!), and put poisoned bate in their holes. Any suggestions?

The famous 5-gallon-bucket chipmunk trap:
http://forums.gardenweb.com/forums/load/ipm/msg0502514826494.html