One of the most rambunctious terriers, the Jack Russell Terrier is one of the most intelligent canines in existence. Like all terriers ("earth doggies"), the Jack Russell was bred for hunting, specifically from the original fox terrier breed, by Reverend John Russell in the mid- to late-1800s in Devonshire, England.
Everything about the dog was designed with one purpose in mind: fox hunting. Size, coloration, temper, flexibility, digging ability, intelligence--all these factors combined contribute to the dog's tenacity and independence. In fact Jack Russell Terriers retain most of the physical characteristics of the original turn of the century fox terrier breed; most of the characteristics of that breed have changed enormously to the point where the modern fox terrier has less in common with its ancestors than does the Jack Russell. Jack Russell devotees take particular pride in the breed's characteristics, and they are wildly popular in England, with popularity on the increase in the United States. Probably the most well known Jack Russell is "Eddie", the dog owned by Frasier Crane on the TV show "Frasier".
Like all terriers, the Jack Russell isn't well suited to city living, or confined quarters. They love to dig, and must be trained not to do so when very young. They are remarkably gentle with children. However, they do not tolerate rough treatment, so it's advisable that any children be past the toddler stage before getting one of these dogs. They also are harder to train to tolerate other household pets--it is not advisable to have more than 2 Jack Russells in any one home, as they are highly aggressive towards other dogs, especially other terriers. They also will consider any rodents in the house, your guinea pigs and rabbits included, as fair game.
Despite all these caveats, Jack Russells make excellent family pets, being extremely devoted to their masters. They just need extra attention and training, but the investment will reward the proud owners with a unique, loyal, and keenly intelligent pet.
Jack Russell Terriers, ideally, are no taller than 12 to 14 inches (measured at the withers), and weigh between 13 and 17 pounds. Their short, coarse fur is predominately white, with tan, brown, or black mottled spots. As with most terriers, they actually have two coats of fur, with the undercoat being shorter and denser than most other terriers. They are generally healthy dogs, with an average lifespan of approximately 12 years. They can be prone to cataracts and glaucoma in old age.
Information for this writeup adapted from information found at The Jack Russell Terrier Club of America, www.terrier.com