William, if it is squirrels then an electric net will deter them quite well. My brother used to have trouble with squirrels in his nut
trees, electric net with a 10 joule charger did the trick and in a few cases even gave him some meat for squirrel stew.
In the world of electric
fence and net it is the joule count that matters, the higher joules give more intense shocks, for squirrels you would need around a 4 joule shock to deter them from ever trying again without the possibility of the shock killing them.
I have a charger that puts out 25 joules (this is enough
energy to kill a dog, or energize 4 miles of wire for
cattle deterent), I have never used this charger (it's made from the power unit of an old neon sign).