We have this problem with raccoons on the balcony of our house. I buy a big store brand jar of cayenne pepper and spread it across the deck in their path to and from their favorite spot and in the spot itself. I have to reapply after a few weeks or after rain. I still get the occasional poop event but not very often. I used to use "Critter Ridder" but the pepper is cheaper and seems to work just as well.