The Root of the Behavior
Smaller dog breeds tend to have higher levels of anxiety and are more prone to compulsive behavior. This includes digging. They may not be trying to dig themselves a home or store a bone, but rather have found digging to be an efficient way for them to relieve some stress and anxiety. This is often the cause of digging in all breeds of dogs. Hairless Terriers, in particular, have additional challenges that digging can help protect them from. A hairless dog is far more prone to sunburn than a dog with hair, this would be counteracted if they are covered in dirt or seek some shelter under the Earth. Regardless of the cause of these behaviors, there are things you can do to prevent it in the future! The first step is to identify why they are digging and targeting that root cause with specific measures. These steps may not be 100% effective but should at least reduce the compulsion to dig.
Encouraging the Behavior
Provide them an area in the home that is as far removed from the hustle and bustle of your household as possible. Include a blanket or pillow they enjoy, some toys to occupy their time, and a environment removed from outside sounds. Many dog owners simply use the kennel for this, and canines typically react well to it provided the kennel has not been used as a method of punishment for the canine in the past. A potential positive side effect is that they will start to enjoy their kennel and often retreat to it on their own volition. Canines who suffer from forms of anxiety will also find comfort and relief from an area like this.