According to www.dogbreedinfo.com, the Jack Russell Terrier was developed in 19th century England by a clergyman named Jack Russell. This feisty little terrier was used to hunt small game, particularly fox, by digging the quarry out of its den. Breeders have emphasized its working ability, so the standard is very broad, encompassing a wide range of accepted body types. On English hunts, the Jack Russell Terriers were supposed to be long-legged enough to keep up with the hounds. The energetic and playful Jack Russell makes a good family companion. The Jack Russell Terrier is a perky, merry, devoted, and loving dog. Spirited and obedient, yet absolutely fearless. Careful and amusing, he enjoys games and playing with toys. Friendly and generally kind to children who have been taught not to tease or strike the dog. They are intelligent, yet willful and determined. They have strong hunting instincts (stronger than your average terrier) and should not be trusted with other small animals. They like to chase and explore. Be careful not to let them off the lead unless they are very well-trained. Jack Russells like to bark and dig. They tend to get restless and destructive if not kept fruitfully occupied and well exercised. Jack Russells climb, which means they can climb over a fence, they also jump. A Jack that stands 12 inches high can easily jump five feet. JRTs are not the breed for a inexperienced dog owner. This is a BIG dog in a little dogs body. The owner needs to be as strong-willed as they are, or this little guy will take over.