There could be a number of things living inside your walls, from pests like mice and rats to rodents like squirrels and raccoons. The best way to get rid of them is by trapping or baiting them. You can buy traps at most hardware stores, or use natural materials like peanut butter or oatmeal to bait the critters. Once you've caught them, be sure to release them far away from your home so they don't come back.

Trapping the animals is the most humane way to remove them. One can purchase a live trap at most hardware stores or online. Place bait (peanut butter is a good choice) in the back of the trap and then set it in an area where you have seen the animal(s). Once caught, release the animal(s) far away from your home. If there are a lot of animals, then you may need to set multiple traps. If you are uncomfortable trapping the animals yourself, then you can call a professional pest control company to do it for you. However, this will be more expensive and may not be as humane as doing it yourself.