Red-backed vole eating Cymbidiums (roots & bulbs)
 

Discovered this unwelcome visitor yesterday. I saw the culprit, so I am certain of the identification.

What are the most effective counter measures?

Do snakes eat voles? Perhaps a nice snake free in your growing area will discourage them? Or a hawk? Cat? I think you can buy a cat for about 25$. This may seem stupid, or like a troll, but a cat will keep out a lot of "critters" without poison, or any bad stuff.