As a kid mom always had at least 1 Siamese cat in our household. All were female. I remember from time to time the local resident tomcats would come around the house at night, howling up a storm looking for sweet kitty. Mom did not approve, and took to keeping a bucket of water with some ammonia added at a convenient 2nd floor window. When Tom began a howling, he was greeted with a bucketful of stinky water. I don't think any of the toms ever got substantially soaked with the concoction, but it sure seemed to discourage their desires to meet up with the sweet smelling felines of the household.