Mice, how to stop them?

We have six cats, never seen a mouse around, but some critter chewed the insulation off the alternator cable connectioon on my Subaru, which sits outside. The hood clearance is less than an inch in that area, but something got in. I could see tiny tracks in the dust along the intake plenum tube. Maybe we are feeding the cats too well, and they have lost the hunting instinct. So far, no mice probs with the Prius.

 

Here's the old thread on how/where to cover, with pics.
Guess I'll have to do this soon. We get mice in our garage in the winter too.
Even though I've plugged every possible opening I could find, one never can be
too cautious with these guys...

http://priusonline.com/viewtopic.php?t=603...7a2a1357718e28f