Re: Squirrel Deterrent
Someone mentioned chipmunks. An excellent way to thin the herd is to half fill a 5 gallon bucket with water, then sprinkle sunflower seeds on top to make it appear solid to our furry friends. Then place the bucket near a common gathering place (next to a wood pile is excellent) or construct some sort of ramp for them. They will then set about committing suicide lemming style. I can tell you from experience they sink so be sure to check the bucket daily. If you don't, they eventually float...but by then they sure do stink.
BTW, one nice thing about squirrels in comparison to mice, they seem to be less inclined to chew on wires (in my limited experience with them taking up unwanted residence.) In cleaning out my boat post purchase a year ago, I found a few dozen chewed up walnut shells and a mess of nesting materials that had to be from squirrels. While they enjoyed chewing up some foam and carpet they didn't mess with any wiring thank goodness. The buggers were nesting/living under the deck

The boat now resides in my garage. I put out mothballs, mouse traps and have a cat to boot so there shouldn't be any trouble this winter. I made it through last year just fine.
For the folks parking their boats outside, I would try borrowing a litter box. On a different but related topic, mothballs seem to have chased away a skunk that spent a few nights under my deck last week. I'm keeping my fingers crossed. (especially since my dog is dumb enough to go after it given an opportunity. She loves to catch woodchucks and squirrels.)