My brother had the same problem. He set up a baited spin wheel over a 5 gallon pail. On the plates of the wheel he glued some nuts. Put the pail in his backyard next to a tree. The squirrel would climb down the tree, get on the edge of the bucket and when it stepped onto the spin wheel, it would fall into a foot and a half of water. Two weeks later there was only four squirrels around and they wouldn’t even get close to the bucket.
LOL....I’ll have to remember your brother’s invention. What a great solution.