The rat terrier Chihuahua is a mixed breed that is one part rat terrier and one part Chihuahua. These dogs are also known as the rat-cha or rat-chi and chia-rat.
Breeding a purebred rat terrier and a purebred Chihuahua results in the designer breed known as the chia-rat. These rat terrier Chihuahua mixes are considered crossbreeds, not purebred dogs.
The chia-rat should weigh between 2 to 4 pounds and stand about 5 inches tall. They are slightly longer than they are tall and have a long, narrow, gently curved tail. Chia-rats have large ears, well-built bodies and petite feet with strong digging claws. Color combinations seen in these dogs are sandy white, blue, mole, black and tan.