The cats round here are a pain in the arse, no sooner have I prepared an area for sowing or planting and they start using it as a toilet. I read somewhere that cats don't like snakes so I thought I'd set up a few decoys.
Bits of hosepipe seem to seem to work OK:
So do toy snakes, these even glow in the dark:
It could be a fluke but so far so good.