Dogs dig for a variety of reasons. Instinctive traits, boredom, to bury bones, make a cool pit to lie in, or some dogs will even dig to follow the sound of water rushing through pipes.
Dogs dig out of boredom
The dog could be bored during the day, so there are lots of toys aside from the digging toys that you may like to get too … there are things like a Kong or food cube that occupies his mind and tummy; a boomer ball that is completely solid and he will not be able to break it, etc.
You can try various things, putting their feces into the hole and covering them, putting in water balloons, using Tabasco or Cayenne Pepper, etc., to sprinkle on an area you want them to stay away from.
Obedience training with diversity keeps a dog’s mind active, which reduces boredom (and, many times, digging). The more unpredictable you are with giving your commands, the more reliable your dog becomes performing the commands. You could also teach him to LEAVE IT (which I find a handy command and use everything from food to other dogs). You must catch him in the act. Just make sure you don’t call him with COME and then tell him off. You will end up with a perplexed dog that won’t come back when called.
Create a digging pit
It is similar to a child’s sandpit but is specifically for your dog to use when you go out. To encourage your dog to dig bury a specific toy (or toys) each day of the week, e.g., you might bury a ball and a Frisbee or a bone on Mondays … you bury the objects before you go out, so there is something new to find. Then take those toys away Monday night or Tuesday morning and put in a couple more different things, and so on.
Use Snappy Trainers
You could also use Snappy Trainers … they look like (and are approximately the size of) a mousetrap, but instead of the wire, big plastic paddles on them so they won’t hurt the dogs. When the dog sticks their nose into an area where you have a Snappy Trainer, it will set off and makes a loud snap which is often enough to put a dog off from digging.
No matter what you try, consistency, repetition, and persistence are required. On average, it takes 150 repetitions to be retained in a dog’s short-term memory. So stick with it!