The Formosan Mountain Dog, commonly referred to as simply Formosan, and also known as Taiwan Dog (traditional Chinese: 臺灣犬) or Taiwan Native Dog (traditional Chinese: 臺灣土狗) is a breed of dog indigenous to Taiwan. Formosans are further classified into Taiya (Atayal), Bunon (Bunun), and Plain based on various physical characteristics. Originally kept by aboriginal Taiwanese as hunting dogs, purebred Formosans are extremely rare, so much so that one dog breeder in Taiwan named Chen Ming-nan spent 10 years to find four dogs suitable for breeding.
Chen owned a Formosan as a child, and in the 1980s he established a business dedicated to creating a pure-bred Formosan, beginning with a single puppy that he purchased for NT$30,000 (about US$1,000) from an aborigine man. Characteristics include medium size, firm jaw strength, and triangular face, with upright or semi-folded ears. The tail is upright or curved with a thick coat, but the belly is hairless; the tail is used to warm the belly, and may even be long enough to protect the snout from insects. According to Chen, there is no shortage of stray dogs in Taiwan that could be mistaken for a pureblood Formosan, but purebloods tend to have a strong sense of direction, smell, sight, and hearing.
Of the purebloods that Chen found, blood tests showed that they were related to dogs found in Southern Japan and that they were descendants of the South Asian Hunting Dog. Little known outside of Taiwan, Formosans are recognized with a pedigree from the Taiwan Kennel Club and the International Canine Organization. They are well adapted to the uneven and thickly forested terrain of Taiwan, having become a semi-wild breed prior to the arrival of human Dutch settlers. Notwithstanding these adaptations, Formosans retained the potential to be trained, and are now used as hunting dogs, as guard dogs, as stunt dogs, or simply as companions.