The Chihuahua is the smallest dog breed in the world and is also the oldest breed in America. The breed takes its name from the state of Chihuahua in Mexico where it was discovered in 1850. It is believed that the Chihuahua descended from Chinese hairless dogs which crossed from Asia to Alaska on a land bridge before continental separation and bred with the ancient Aztec Techichi dog. The fist one was registered with the American kennel club in 1905.

They are well known for their small size, large eyes and large ears. Their coats comes in two varieties, smooth and long. The smooth coat variety has a short, glossy, soft coat over the entire body which is thinner on the head and ears whereas the long coat has a soft, long, sometimes very thin coat which can be slightly curly or flat. Both coat types have a variety of colours including fawn, black, brown and white. There are many colour patterns and mixes including Blue Brindle and Chocolate and Tan.

The Chihuahua is noted for its fierce devotion, loyalty, ferocity and personality. They become extremely attached to just one or two people and become very protective. Their small size means they are suited to apartments as their exercise needs can be fulfilled indoors with toys and play sessions, although they do enjoy going for daily walks with their owners.

They can adapt to living in most environments but they are not good with children or other pets as they can bite when frightened, they seem to have no concept of size and will attack larger animals which often results in injury. They are wary of strangers which make them good guard dogs. Chihuahuas are often thought of as high-strung but if correctly trained they can become excellent companions.

They can be difficult to train but with the right amount of patience and commitment they can do well. They need positive reinforcement and intensive socialisation is essential from an early age. Owners must be careful not to overfeed Chihuahuas as it can lead to diabetes, joint injuries and bronchitis. The breed also needs veterinary care for things such as birthing and dental care.

These dogs are prone to the painful disease called Hyrocephalus which can be diagnosed by the puppy having a swollen head; it will also be lethargic and grow more slowly than siblings. The breed is also known for their moleras, a soft spot in the skull, they are the only breed to be born without a complete skull. The molera fills with age but great care should be taken during the first six months until the skull is fully formed.

Chihuahuas do run the risk of low blood sugar which can lead to coma if unattended. They have also been known to suffer from eye infections due to their large eyes and low ground clearance. The breed has a tendency to tremble but this is not a health issue, it normally happens when the dog is stressed or excited. They have the longest life span of any dog and can live up to 18 years.