Rat Terriers usually have natural erect ears and an alert expression.

The Rat Terrier ranges from about 10 to 25 pounds and stands 13 to 18 inches at the shoulder. The miniature size (13 inches and under as defined by the UKC) is becoming increasingly popular as a house pet and companion dog. A larger strain, often in excess of 25 pounds, has been developed. These Deckers or Decker Giants were named after a breeder named Milton Decker to create a larger hunting companion and are recognized by the National Rat Terrier Association (NRTA, see Breed recognition below). The NRTA recognizes a Toy Variety weighing 10 pounds or less, and continues to classify the Teddy Roosevelt Terrier as the Type B Rat Terrier. In any event the Toy and Miniature Rat Terriers display the same hardiness, prey drive, and stamina as their Standard sized counterparts.

[edit] Temperament

Although often mistaken for a Jack Russell Terrier, the Rat Terrier has a different profile and a very different temperament. Rat Terriers are finer of bone and have a more refined head. They always have a short single coat—never wire coated. Rat Terriers tend to be less aggressive than Jack Russells; while they have a definite terrier personality they also have an "off switch" and love lounging on the sofa in a lap as much as tearing about the yard. Rat Terriers are normally cheerful dogs but they tend to be more sensitive than Jack Russells to changes in their environment, owner's moods, or to unexpected noises, people, and activities. The "social sensitivity" of Rat Terriers makes them very trainable and easier to live with for the average pet owner but it also means that extensive socialization from an early age is critical. Proper socialization of a rat terrier puppy includes exposing the animal to a wide variety of people and places, particularly during the first 3 months of life. Like most active and intelligent breeds, Rat Terriers tend to be happier when they receive a great deal of mental stimulation and exercise. ΐ]

Rat Terriers can be kept easily by pet stores; as a result, many commercial breeders produce puppies quickly and do not take the time to socialize and place puppies responsibly^{[citation needed]}. Rat terrier owners therefore consider going through a rescue service to be a more humane and preferable way to obtain a pet than buying from puppy mills or careless breeders^{[citation needed]}.