From my experience, even if thorny (or poisonous), cats may chew on a leaf (or two, or twenty) and/or have their romp and still dig and deposit in the garden.

A lot depends on the individual cat and what works best as their deterrent. Is it YOUR cat, or belongs to someone else? And what are they doing that you want to stop?

That does make a difference. :-/

~Sara (cat behavior specialist)

The cats are the pets of unknown irresponsible people who may live in a neighboring street.
It goes without saying people do not want other peoples cats on their property pooping in their gardens and creating a mess and nasty odor. That is the main reason most people don't want cats in their gardens.
I am surprised to hear that cats would just walk right through and ignore painful, sharp thorns from prickly bushes and groundcover.

What we may consider sharp and painful, is tolerated easier by animals that have thicker skin and a svelt coat of fur as protection. I've seen cats go through very thick briars when they are determined. And cats can and will be stealthy (leaping over 4 ft shrubs, finding a way around, or even digging to get to what they want.)

But don't distress. There are a couple options for you since they are not your pets. And even if they were, this still would work but there are other things you could do if they did belong in your care.

Scarecrow motion activated sprinklers come to mind (you can Google it). They activate when there is motion in the garden (up to 35 ft), run for a very short time, then auto shutoff, and can cover a pretty large area. Not many cats stay around for that. (Just remember to turn it off when you need to personally tend your plants, hehe.)

Other option takes more effort on your part. Go get yourself a Nerf gun, or soft-air gun (that shoots the plastic BBs). Camp out quietly away from the area but in range of targeted area. Cats respond best to this method if they are "caught in the act" of doing whatever is offensive to you. After a time or two getting caught, they "generally" find other yards/places to bother.

Both cost about the same, just depends on your time available, hose availability, and plant sensitivity to having a small shower or two when predators are around.

Hope this helps. :-)

I know cats have fur on their bodies, but what about their feet? Are the underside of their paws impervious to sharp objects? If there is a groundcover that has sharp thorns, in the area were I want to keep them out of, then the would not be an option to jump over or dig around it.

Is there any type of spreading groundcover that contains razor thorns throughout it?