When Rat Terriers were originally bred, they had one job to do. That was to keep the rodents away. It did this job very well, but its role has changed through the years. Today, this breed of dog is primarily kept as a loving pet all across the world, primarily in the United States. These are very sturdy small dogs that generally come in two sizes. One is slightly larger than the other, but neither dog is very large at all. Rat Terriers are relatively strong dogs for their size and they come with short fur, although there is a hairless version available. That one is called the American Hairless Rat Terrier. This intelligent and energetic dog, while once popular on farms and large properties, is today a great family pet to own.