When people learned to farm they needed, for the first time, to house large stores of grain. With such an abundant food source, the rodent population multiplied. Cats were good, but when rats raided the rations, weasels were in the hen house, and gophers were ruining our fields, we needed reinforcements. We created terriers.
Hard-nosed, hard-fighting, hard-living dogs that would be beer-guzzling, bar-fighting, football-playing, barbell-lifting guys if they were human.
Imagine a small dog going down a hole in pursuit of some panicked animal. Many feet below the surface, the animal and the dog have it out. The animal is fighting for its life - biting and scratching for all he is worth. The terrier takes the pain and keeps on going. In fact, the pain spurs him on. Humans call that a "game attitude"; terriers call it just plain fun.
Once a terrier goes down a hole, he often finds it impossible to back out. That's why they bark. The owners located their terriers by the yapping then dug them free. All the silent terriers perished long ago down various beasties’ holes. What kind of dog did this work typically create?
Fearless
Here's a dog that is not intimidated by much. A larger dog? Ha! The bigger they are the harder they fall. A truck? He'll try to stop it. They are courageous to the point of brashness. As a terrier owner, it is your job to protect them from themselves by keeping them safely contained in a secure fence or on lead. Not every terrier will start a fight, but few will walk away from one.
Predatory
Terriers, as a group, chase. If not trained otherwise, squirrels, mice, even cats are fair game. Once they are launched, they will often fail to respond to command until the chase is completed; that might be across a four-lane highway. They are not to be trusted off lead.
Excavator
If you don’t mind craters this is not a problem. Some people give their diggers a designated digging zone, others resign themselves to potholes, others confine the dog in a dig-proof kennel and more do not leave their dogs outside unattended. One thing is for sure, punishing a terrier for digging is about as effective as punishing him for breathing.
Vocal
"Barkiness" ranges in all breeds but, for more than a few terrier breeds, barking is simply what they do. They bark when they are excited, frustrated, annoyed, anticipatory, bored, or happy. Redirecting barking by having the dog lie down or get a toy can help, but don’t expect complete silence. If you want a non-vocal dog, don't get most terriers.
Tough When Excited
This is a tricky one. It isn't that they like pain; it's just that once they are stimulated, they don't react to it in a "normal" way. A terrier can be quite sensitive when calm. At those times a firm tone of voice is quite effective. But once your dog is spitting canine cuss words at the neighbor's dog, even strong corrections may fail to interrupt the behavior. In fact, they are likely to spur the dog into a greater frenzy.
Common Problems: Barking, Jumping, Aggression (All Types), Leg Lifting, Digging, Dog Fighting, Chasing Other Animals, Hyperactivity, and Running Off.
The Good Home: Households with older children and adults with time for daily romping. Training should be viewed as a spiritual experience where the process is as important as the goal. A sense of humor combined with a will-of-steel is mandatory. If you're impatient, controlling or self-serious, get another type of dog. Stay calm, be persistent and it will all work out...eventually. Never give up; your terrier won't!
Note: Over time, some of the terrier breeds have “softened” quite a lot and are not nearly as feisty as they once were. So research the breed you want carefully and know exactly what you are taking on.