Unlike most other canine breeds whose ancestry is known, the history of the Chihuahua remains a mystery. Popular speculation attributes the Chihuahua to Mexico where uncovered ancient figurines offer an insight into the evolution of the breed, whilst suggesting they were selectively bred as a companion dog in the Toltec civilisation. The Chihuahua is also mentioned in early colonial records, which refer to miniature, partially hairless dogs at the beginning of the 19th century.
There are two common breeds of Chihuahua: the Smooth Coat and the Long Coat. Both types are well defined, with proportionate limbs and are common in a variation of colours, from chocolate brown to fawn, to mottled white and black. The Chihuahua has a short snout and a relatively long tail in relation to its overall size. Perhaps the most characteristic feature of the Chihuahua is in fact, its size, measuring an average of 15cm tall.
Despite its reduced size, the Chihuahua is a notoriously protective and feisty breed, content to exercise in small outdoor areas such as back gardens, and companionable with other animals. With a characteristically loud bark, the Chihuahua will make itself heard in order to gain its owner's attentions. Susceptible to over-feeding, the breed's healthy, average weight is between 1.8-2.7 kg. When shown appropriate care, the Chihuahua has a life expectancy of up to 15 years.
Whilst minimal care requirements exist with this breed, the Chihuahua is susceptible to a number of health complaints; anything from genetic neurological disorders, to hypoglycemia and various weight-dependent illnesses. Notably, the Chihuahua is the only canine breed to be born with an incomplete skull, in the same way that human babies are. This is not a defect, however, exaggerated care needs to be ensured in the first six months of life in order to prevent injury to the un-formed membrane. Chihuahuas can also suffer from a myriad of weight-related complaints, including dental disease, hypoglycemia, joint deterioration and chronic bronchitis. Feeding a Chihuahua human food is not encouraged, as the breed's reduced size means that even the smallest amount of fat can lead to weight gain.