We used to have lots of squirrels that would empty our feeders. We installed them far enough from trees so that squirrels could not jump to them, and then mounted them on metal poles. Not enough! We had to grease the poles with axle grease!!! Success - and a great source of amusement until the squirrels figured out that climbing was useless. Have you ever seen a squirrel sliding down a greased pole? I don't know what you would want to use on a cat that wouldn't harm it - since cats lick themselves clean - but there might be something - even Vaseline, I don't know.