The Jack Rat Terrier is a small dog descended from two hunting breeds: the Jack Russell Terrier, of English origin, and the Rat Terrier, an American breed that started out as a pest exterminator around farms.
The best of the breed possesses its parents' speed and topnotch hunting abilities, as well as their intelligence, trainability, and considerable level of energy.
The Jack Russell Terrier was primarily a fox-hunting dog, bred by Reverend John Russell to bolt foxes from their dens and stand out in the field in a largely white coat while holding the quarry for its master. The dog is well-balanced in body, with legs long enough to keep up with larger hunt hounds, yet the chest not to deep to be able to delve into foxholes. The prey drive is high, and indoor living is not really suited to them because of their need for wide open space and vigorous activity.
The Rat Terrier is prized for its speed and agility in the field, and warm, gentle disposition whenever indoors with a family. Its ancestors were most probably "pit" dogs used in ratting or rat-baiting, a common preoccupation among British gamblers in the early 19th century. Modern day Rat Terriers can be relied on to rid a household or farm of vermin, and also be a loyal companion on hunts for small game.
The Jack Rat Terrier, if taking after the Jack Russell Terrier, will be mostly white, with black or tan markings. The Rat Terrier parent will give a wider variety in coat color: brindle and tri-color in combinations of white, black, tan, red, and yellow.
Coats may be smooth or "broken" double-coats, or a single coat with short fur. The double-coat, if smooth, will be shorter all around than a broken coat, which could be longer around the face or tail.
A Jack Rat Terrier, if properly crate-trained and sufficiently socialized from puppyhood, will be a relaxed, affectionate indoor family animal that will exuberantly play with children. It might take roughhousing for abuse, however, and an independent, confident animal such as this will not stand for it, so children should be supervised.
Sensitive to moods and eager to please, a Jack Rat Terrier will tag along after its owner looking for affection, and will not like strangers coming up on them. They even take some time warming up to strangers who are introduced to them.
They can be stubborn and fearless, traits that might serve them well in the field, but could get them into trouble with other animals around the house. Boredom, too, should be avoided at all costs for these dogs. Their intelligence will serve them a bad turn if they are under-exercised or left alone too often, as they will find ways to amuse themselves.
Coats are low maintenance and can do with brushing once a week. Bathing regularly isn't necessary, only as needed to clean out dirt and mud, or to take care of the "dog" smell.
Puppies are best crate-trained, to curb chewing. Constant exposure to other dogs will dampen the aggression as they grow older; however, an owner must establish leadership early on, as the breed can be stubborn, and will assert itself over and over when it think it can get away with it.
Leashed walks will prevent a highly energetic dog from taking off when scenting prey and giving chase. A yard and an hour of tricks daily, plus a walk or two, would nicely fit the Jack Rat Terrier's need for mental and physical stimulation. This hunting breed and working breed has a lot of stamina built-up; an active owner up to the physical demands will appreciate it most.