Jack Russell terriers usually weigh between 14 to 18 pounds and stand between 10 and 15 inches in height. This breed has a compact build with a body length that is proportioned well with its stature. The Jack Russell terrier has a balanced muzzle and strong jaws.
In 19th century England, the Jack Russell terrier was a popular choice for fox hunting due to its small size, which was beneficial in flushing prey out of dens. The Jack Russell terrier is characterized by its intelligence, courage and cheerfulness. Due to its breeding, the Jack Russell terrier has highly developed hunting instincts and can grow restless if not given proper attention and care. It is not recommended to leave small animals alone in the presence of this breed.