The Chihuahua ( (listen); Spanish: chihuahueño) is the smallest breed of dog, and is named after the Mexican state of Chihuahua. In a 1520 letter, Hernan Cortés wrote that the Aztecs raised and sold the little dogs as food. Colonial records refer to small, nearly hairless dogs at the beginning of the 19th century, one of which claims 16th-century Conquistadores found them plentiful in the region later known as Chihuahua. Colonial records refer to small, nearly hairless dogs at the beginning of the 19th century, one of which claims 16th-century Conquistadores found them plentiful in the region later known as Chihuahua. Small dogs such as Chihuahuas were also used as living heating pads during illness or injury. This is a fairly common cause behind any pacing, excessive salivating, destructive chewing, or barking, howling, or whining in dogs. Many treatments and tips can help prevent separation anxiety in dogs.