I was thinking about putting a strip of bird spikes along the circumference of the pot, but with 6' pots that requires about 19' of strip, and the strips are quite expensive, roughly $3/ft even in bulk packs. I don't THINK I've seen 'em climb up the pot and attack from surface of the pot, but I've seen some suspicious looking mini-piles of dirt and potentially a collapsed tiny tunnel, but can't be positive. Perhaps a ground mouse, some other burrowing animal besides gophers that typically leave a much more noticeable dirt mound.