This behavior does not make Dallas a "bad dog". If labeling a dog's behavior, it is important to remember that different breeds of dogs were bred to do specific jobs and certain behaviors are the result of their family history and DNA. Other members of the herding group, including Border Collies, the Welsh Corgie, and German Shepard, will all instinctively react in a similar manner.
Does your pup chase after squirrels and other small animals? Spaniels, Retrievers, Setters, and Pointers are members of the Sporting Group and are very high energy, and were bred to chase and retrieve.
Knowing how your dog will react in certain situations is the best way to prevent unwanted results from certain behaviors. One of my walking buddies is a large pup with Golden Retriever ancestors Although he walks well on the leash he will react strongly to other dogs he sees out for walks. At first he will stop and look but if the other dog reacts he is ready for the chase. To minimize the unwanted behavior I stay aware of our surroundings and activity in the area, making sure to keep a good distance from other dogs, approaching only after he has been calmed.
Left out in a yard, is your pup's favorite activity digging holes? If your dog's ancestry is part of the Terrier group your pup probably has an inbred instinct to dig. The Terrier group includes Jack Russells and West Highland Terriers among many other breeds and mixes.
For dogs with Terrier ancestry is is best not to leave them out in a yard unattended. Dogs of this breed are very high energy and will channel that energy into doing what they do best - digging holes. Providing an area for your pup where they can dig and retrieve will help change this behavior from destructive to constructive. A sand patch in a backyard area designated for your pup to dig will discourage digging in unwanted areas. This area can be made extra attractive by burying toys for your dog to find.
If you live in a area with snowy winters you can use this to your advantage and create a fun activity for your Terrier. Throw balls and other toys that will sink in the snow and watch your dog have fun digging to find their treasures.
Knowledge of your dog's breed and understanding of their behavior will prevent your pup from being labeled a "bad dog". Remember, what they do may be the result of their family history and DNA. Instead of trying to change your pup, anticipate their actions and find creative ways to channel the energy into more acceptable behavior for their, and your, happiness and well being.