Dogs dig for many reasons, which may include:
Regulation of body temperature
Offer your dog cool locations on hot days or heated areas on cool days.
Play and exploration
Help your dog get plenty of exercise and give him lots of attention.
Determine a diagnosis and treatment plan with your veterinarian to deal with your dog’s specific anxiety.
Remove the prey from the environment.
Block off digging areas near fences and limit unsupervised access by kenneling your dog or keeping it inside.
You may want to try to make unacceptable digging areas unattractive by placing booby-traps such as motion activated sprinklers or rocks in those sites.
Recreational digging — for fun!
Provide your dog with an acceptable digging area to allow him to engage in this normal behavior in a positive way. Use soft, loosely packed dirt and bury things that a dog may like to dig up.