In my part of the country, we are constantly trying to keep the critters out from under our sail/bimini covers, as they love to get in there, build a nest and make a big mess, especially on white sails. Even when we knock down the nests, they leave brown stains. About two months ago I started putting strips of Bounce fabric softner on each snap along the bottom of the sail cover and on the part of the cover that is secured along the forward part of the mast. They work...have not had a critter of any sort get up in my sail yet this summer.