If you are the type that can't stand killing animals, but you also don't want mice running around your garage, then you are probably confused as to what to do. Most solutions that you read about online include some variation of glue traps, spring loaded traps that snap necks, or poison pellets. However, there are other solutions. There are methods that you can use that will chase the mice away, or even methods that will humanely trap them and then you can release them outside of your garage. Here's a bunch of ideas.
An interesting way to keep mice out of your garage is to use predator urine. You can get coyote urine from a hunting supply store. The mice will smell this urine and stay clear of the garage because, in the wild, coyotes will eat them. The scent is not so powerful that it will overwhelm human nostrils, so don't be concerned that when you walk into the garage you will get a terrible scent.
An Owl Replica
Another idea to consider is to use a replica of a predator, ideally an owl. You can get plastic owls and situate them on the exterior of the garage so that mice will see them and be hesitant to enter into the garage. You can get plastic owls that have a swivel design head that bobs in the wind, this gives it the appearance of being a living, breathing, owl.
Peppermint Extract Spray
Another non-lethal idea is to get a bottle of peppermint essential oil and add it to a spray bottle of water. Then use this spray bottle to mist around the floorboards, and along the outside perimeter of the garage. The pungent, strong scent of the oil will help to deter mice from hanging around, as they find it unpleasant.
Humane Mice Traps
If you find that the mice simply won't stay away, and you want them gone, then you should look into humane traps. You can get a rodent exterminator to come in and set the traps. They are comfortable dealing with mice, and they will also know where to set the traps. Just tell them that you don't want them to use any sort of poison, glue trap, or spring loaded-neck breaking design. The professional will set the traps along the paths the mice use to travel (which is something you might not be able to locates, as you are not an expert in rodent behavior) and then they will come back and remove the traps and free the rodents when you are done. If you are suspect that they will just kill the mice, you can have them release the mice under your supervision at the edge of your property. Just make sure that you have sealed up all the little nooks and openings in your garage before you release the mice so they don't try and run back in at a later date. You might also want to line the exterior of the garage with mothballs and peppermint oil to further deter the mice from returning.
To learn more, visit a website like http://www.greenleafpest.com.