<P> Due to their working nature, Jack Russell terriers remain much as they were some 200 years ago . They are sturdy, tough, and tenacious, measuring between 10--15 inches (25--38 cm) at the withers, and weigh 14--18 pounds (6.4--8.2 kg). The body length must be in proportion to the height, and the dog should present a compact, balanced image . Predominantly white in coloration (more than 51%) with black and / or brown and / or tan markings, they exhibit either a smooth, rough or a combination of both which is known as a broken coat . A broken - coated dog may have longer hair on the tail or face than that which is seen on a smooth - coated dog . The skin can sometimes show a pattern of small black or brown spots, referred to as "ticking" that do not carry through to the outer coat . All coat types should be dense double coats that are neither silky (in the case of smooth coats) nor woolly (in the case of rough coats). </P> <P> The head should be of moderate width at the ears, narrowing to the eyes, and slightly flat between the ears . There should be a defined but not overpronounced stop at the end of the muzzle where it meets the head, and a black nose . The jaw should be powerful and well boned with a scissor bite and straight teeth . The eyes are almond shaped and dark coloured and should be full of life and intelligence . Small V - shaped ears of moderate thickness are carried forward on the head . When the dog is alert, the tip of the V should not extend past the outer corner of the eyes . The tail is set high and in the past was docked to approximately five inches in order to provide a sufficient hand - hold for gripping the terrier . </P> <P> The Jack Russell should always appear balanced and alert . As it is primarily a working terrier, its most important physical characteristic is its chest size, which must not be so large that it prevents the dog from entering and working in burrows . The red fox is the traditional quarry of the Jack Russell terrier, so the working Jack Russell must be small enough to pursue it . Red foxes vary in size, but across the world, they average from 13--17 pounds (5.9--7.7 kg) in weight and have an average chest size of 12--14 inches (30--36 cm) at the widest part . </P> <P> The Jack Russell terrier and Parson Russell terrier breeds are similar, sharing a common origin, but have several marked differences--the most notable being the range of acceptable heights . Other differences in the Parson can include a longer head and larger chest as well as overall a larger body size . The height of a Parson Russell at the withers according to the breed standard is 12--14 inches (30--36 cm) which places it within the range of the Jack Russell Terrier Club of America's standard size for a Jack Russell of 10--15 inches (25--38 cm). However, the Parson Russell is a conformation show standard whereas the Jack Russell standard is a more general working standard . </P>

What is the weight of a jack russell terrier