I have a fenced in back yard. And I have an armadillo(s) that digs under the fence on one side, and then under the fence on the other side. I don't see any signs of them digging in the yard, so I think that they are just passing through. I've filled in the gaps with dirt, and bricks, and sprinkled in some mothballs (apparently they have very sensitive noses, and don't like strong smells.) And it does seem to work... they don't go under the fence in those spots. Instead, they move down and dig a hole right on the edge of the old hole. And I can go weeks with no sign of them, and then the old holes are dug back out. From what I read they aren't very territorial, so it's hard to get rid of them entirely, since they just sort of wander around randomly.

Now, since they aren't digging in the yard, I wouldn't really care about the holes. But I have a small cat. Smaller than the dillo. So if they can get under the fence, so can she. And I'd really rather have her stay in her yard. So, anyone got any clues about how to fix the fence so that the dillo stays out?

Froggy, even though you aren't seeing them actually dig in your yard, you probably have them living under your lawn. Armadillos get around by digging and creating tunnel systems. They have poor eyesite but an excellent sense of smell. If you have grubs, turf worms, fruit, or a compost pile in your yard, or if your neighbors on either side have these yummy food sources, the armadillos will keep coming back. You have used some good techniques but you are right, it won't get rid of them. Aside from trapping and removing them and filling in the holes the way you have, the only other method that I am aware of that works without hurting them is something very simple. You can create a hot pepper deterrent. Use a blender, some water and hot peppers. Spread this all around the perimeter of your fence. You will need to keep reapplying every week for a while to get them to the point that they realize this is a permanent barrier and this is an area they need to avoid.

Thanks, I'll try that. Any advice on how to make the pepper solution?

Another thing you could try is chicken wire fencing installed on the ground around the perimeter of the fence.
Works great at keeping dogs from digging out, perhaps it would help keep the dillos from digging in.

We put dirt over ours and through some grass seed on top of it years ago and you'd never know it was there.

Hey froggy, I would think that a 1/3 part peppers to 1 part water, should do the trick nicely. So, at this time of year, use the fresh, really hot peppers. More impact than something sitting on a shelf. If you use 1 cup of water, throw a couple of hot peppers in the blender. I don't have an exact measurement for you. There should be enough pepper in the mixture to cause them to turn up their little noses.

I live in Texas. Finding hot peppers will not be a problem!

I've been pondering the chickenwire option. I might try it in the spots where they are actively digging, and see what happens.

And I am fairly sure that they are living in the neighbor's yard. One of the holes goes under the fence right where they have a storage shed backed up to the fence on their side. If I were a betting man, I'd wager that the den is under that shed.

Sounds like it froggy. There has to be a reason for them to be hanging around. They don't just dig tunnels and pass through. They are on the hunt for food. And, chicken wire in selected areas won't work. It needs to be completely around the perimeter of your fence. If not, they will just dig in the unaffected areas.

Hmm, without "you" hurting them, have you considered a Dog? The dog should do the trick. Get a small dog, so it and the cat becomes friends, then the dog will grow and become territorial and keep the armadillos out.
Armadillo defined - an opossum on the half shell.