A dog.
Maybe something like this would work, not sure... http://www.critter-repellent.com/squirrel/squirrel-repellant.php
Plantskydd has an effective, natural rabbit repellent that works up to six months!
Eucalyptis leaves. When my sisters nasty cats had fleas, I put a bunch of leaves under my bed and under the couch and it seemed to work.
Cedar oil is a good natural spider repellent. Simply spray in on the area of concern and the spiders will leave.
Kechara gave you good advice, but I wanted to add on a little. My husband and I go fishing up country a lot and even though they have been given a flea/tick control (Advantage) every time we come...
climbing trees