We're overrun with what I only know as "black squirrels", for the first time in decades. Not the typical gray ones you see everywhere. Someone said they are 'ground squirrels'. These black squirrels tunnel under everything: house, tuff shed, garage, water tanks. They also have a very high-pitched alarm chirp which goes on and on. Caught one yesterday and gave her a new zip code.
I never use the poison baits. There is collateral damage when your half-dead-from-eating-poison mouse staggers out into the open and Mr. Screech Owl or Mrs. Great Horned Owl snags it as a snack. The same poison that gets to your mouse also gets to the owl, in some quantity. Since owls (and other raptors) are the good guys in the battle against rodent pests, makes no sense to harm them, too. Just sayin'.