The breed was developed in Great Britain from crossing the Smooth Fox Terrier, the Manchester Terrier and later on the Beagle and the Whippet when they were introduced in America. There are three recognized sizes for the breed: the Standard variety stands at 14 to 23 inches and weighs 12 to 35 pounds; the Mid-sized with a height of 8 to 14 inches and weight of 6 to 8 pounds; and the Toy variety which is the smallest at 4 to 6 pounds and 8 inches tall. They have compact bodies supported by powerful and agile legs. The Rat Terrier is well-muscled with a deep chest, solid neck and strong shoulders. The ears are typically erect but may be tipped or button. The coat lies close to the body and can come in a variety of colours and patterns. Typical variety is a base of black tanpoint with piebald spotting. Another common colour is blue and brown tricolor.
The Rat Terrier is a working breed used to kill hunt and kill vermins in farms. They are also good companion dogs and watch dogs. Like most terrier type breeds, they display the usual characteristics of intelligence, alertness and feistiness. They are good with children and are eager to please their owner and the family. The Rat Terrier is a well mannered dog that is easy to train and are recommended for owners with active lifestyles. They are good swimmers and love to dig when out in the yard or the park. They are fairly healthy and can live for about 15 to 18 years.