Save the shrews (and wood mice)

So, we have a nasty rat in that hole by the pond. Hubby set two rat traps, but of course what have we caught? A shrew. I want to keep the little guys
They are good for the garden and the little owls in the field. He baited them with choccy and peanut butter. I didn't think shrews would be interested in that but I was wrong.
Any suggestions what to use as bait that will attract a rat but not a shrew, if that is possible.

Any suggestions what to use as bait that will attract a rat but not a shrew, if that is possible.
0
Posts
The compost doesn't seem to attract them now that I have a different system.
We haven't managed to kill one in a trap either. Don't want to leave poison out, it's dangerous to other animals, expensive and I think they are resistant any way. Thinking of flooding its hole. Hubby on standby with the rifle. What a scene
Maybe if you use such a trap you can let out the shrew and mice and do what ever feels right with the rats?
If needed I can recommend a really good humane mice trap we bought on amazon as it works really great for us.