04/07/2026
Overview
The Chihuahua or Chihuahueño is a Mexican breed of toy dog and the smallest recognized dog breed in the world. It is primarily kept as a companion animal and is characterized by its compact size, large erect ears, and rounded skull.
Genetic studies indicate that the Chihuahua retains a small proportion of pre-Columbian indigenous American dog ancestry, distinguishing it from most modern breeds, which are largely of European origin. The breed was formally recognized in the early twentieth century and has since become one of the most popular companion dogs worldwide.
History
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DNA studies suggest that native American dogs entered North America from Siberia approximately 10,000 years ago and were subsequently isolated from other breeds for approximately 9,000 years until the arrival of the first Europeans; these pre-contact dogs exhibited a unique genetic signature that is now nearly extinct. A study based on sequencing of ancient dog genomes, published in 2020, suggests that this pre-colonial ancestry survives in two Mexican breeds, to the extent of about 4% in the Chihuahua (and some 3% in the Xoloitzcuintli). An earlier study (2013) had suggested that the pre-colonial ancestry of the Chihuahua might be as high as 70%.
Colonial records refer to small, nearly hairless dogs from the early 19th century; one account claims that 16th-century conquistadores found them plentiful in the region later known as Chihuahua.In a letter written in 1520, Hernan Cortés wrote that the Aztecs raised and sold little dogs as food.
The American Kennel Club first registered a Chihuahua in 1904, Midget, owned by H. Raynor of Texas.
Characteristics
Chihuahua breed standards specify an "apple-shaped" skull, also referred to as an "apple-dome" conformation.Chihuahuas can appear in almost any coat color or pattern, ranging from solid to marked or splashed, meaning the coat has an underlying darker color with scattered lighter patches. Apple-dome Chihuahuas have large, round eyes and large, erect ears, set in a high, dramatically rounded skull.Chihuahuas have a feature on their heads called the molera, which is a soft spot much like the fontanel found in human infants. It can be hard to see but is easy to feel by touch.The stop is well defined, forming a near 90-degree angle where the muzzle meets the skull.
Dogs of the older "deer" type, with a flat-topped head, more widely set eyes, larger ears, and longer, more slender legs, may still be registered, but the deer head is not considered a separate type in competition and a deer-head dog's digression from the breed standard is considered a fault
Health
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The Chihuahua has some genetic predisposition to several neurological diseases, among them atlantoaxial instability, ceroid lipofuscinosis, congenital deafness, congenital hydrocephalus, muscular dystrophy, necrotizing meningoencephalitis, and neuroaxonal dystrophy; it has a mild predisposition to congenital heart disease. In a radiographical study of canine periodontal disease in 2001, the Chihuahua was found to have the lowest incidence of the six breeds studied.
The predisposition to medial patellar luxation is believed to be significant.
Common health concerns in toy breeds, like the chihuahua, is the fact that they are especially prone to hypoglycemia because of their faster metabolism and greater energy demand relative to body weight, making them more vulnerable than larger breeds. Veterinarians often recommend a half teaspoon of honey as this can be used as at home remedies for hypoglycaemia in less severe cases in puppies. Puppies are more susceptible to hypoglycemia if they are taken away from their mothers too soon. Breeders often give the chihuahua puppies this dose of honey daily to help wean them off of their mother and eventually onto dry food.
A 2018 study in Japan of pet cemetery data found the Chihuahua to have an average life expectancy of 11.8 years compared to 15.1 for crossbreeds and 13.7 overall. 2022 UK study on life expectancy of dog breeds based on veterinary data showed the average life expectancy to be 7.91 for the breed compared to 11.82 years for crossbreeds. 2024 UK study found a life expectancy of 11.8 years for the breed compared to an average of 12.7 for purebreeds and 12 for crossbreeds. A 2024 Italian study found a life expectancy of 8.5 years for the breed compared to 10 years overall.
Such tiny dogs often have difficulty whelping. A UK study found the incidence of dystocia in Chihuahua bi***es to be 10.4 times higher than the average for all dogs.
