Dr. Kano Tadeo, who became an ardent lover of Taiwan's natural environment during the Japanese occupation, once described the wildlife in the alpine areas of Taiwan as having two characteristics. First, a large proportion of the species were endemic. Second, the distribution of species closely related to those outside of Taiwan was discontinuous, often disappearing in certain intermediate regions.

Mistaken

The alpine wildlife in Taiwan was formed one to two million years ago, much earlier than in lower-altitude regions. Between 750,000 to 10,000 years ago, under the cyclic effect of the expansion and withdrawal of glaciers, the average annual temperature in Taiwan could drop as low as five degrees Celsius. This contributed to a high mountain wildlife that preserved certain frigid and temperate-zone plants and animals which had dispersed to Taiwan during the glacial epochs, such as the Formosan landlocked salmon (Oncorhynchus mason formosanus) and Sonani's salamander (Hynobius formosanus). However, these relict glacial-epoch life forms now exist only in segregated ranges and small numbers, on the verge of extinction.

In 1991, Lu Meng-shen, a graduate student of the Department of Biology at Tunghai University, caught an animal during a field trip in Mount Hohuan for her research on the Taiwan vole. The captured animal was not a rodent and weighed a scant sixty grams [2.1 oz]. Thinking it was a young Siberian weasel, Lu released it. Recalling the encounter afterwards, however, she realized that if the animal had been a Siberian weasel, then at that size it should have been a suckling and incapable of moving about independently. She went back to search for the animal so that she could conduct further research, but without success.

In fact, as early as 1969, the National Institute of Preventive Medicine had caught the same kind of animal at Tayuling (a ridge on Mt. Hohuan) and incorrectly labeled the specimen as Mustela sibirica, the scientific name of the Siberian weasel. The specimen was later moved to the National Museum of Natural Science in Taichung, but the coat had not been well preserved and it was dried and shrunken.

Discovery of a new endemic species

The underside of its coat was pure white and was clearly distinct from the brown coat on its back, a trait that set it apart from the Siberian weasel, whose fur beneath is not completely white. Furthermore, it was much smaller than the Siberian weasel, which normally weighs more than three or four hundred grams [10.5-14oz]. We therefore named it the Taiwan high mountain least weasel, with the scientific name Mustela formosana.

There are currently fifteen species worldwide under the genus Mustela, but only the Japanese least weasel (Mustela nivalis) and the ermine (Mustela erminea), along with the newly discovered Mustela formosana, have a pure white coat beneath that is clearly different in color from the topside. The first two species are found mainly in Hokkaido in Japan, northeastern China, Siberia, and the frigid and temperate zones in the higher latitudes of Europe and America.

The Taiwan high mountain least weasel is a slender animal, especially at the head and neck. Its head and torso together measure only sixteen centimeters [6.4 in] and its tail around seven centimeters [2.8 in], roughly one third of the entire body length. The topside of the coat is dark brown with a tint of yellow, while underneath the coat is all white from the cheek to the groin. But there are tufts of brown hair at the lower abdomen area that mingle with the white hair and produce grayish or brown spots. The color at the tip of its tail is darker and some black hair grows, but not so much as to make the tail tip entirely black.

It is known that in places outside of Taiwan, least weasels and ermines turn completely white during winters, save for some black hair at the tail tip. We do not yet know what happens to the Taiwan weasel during winter, but knowing that it seldom snows for long periods of time in the Taiwan alpine areas, it is not likely that its coat turns all white.

After comparing the body size, chromosome and DNA data of the Taiwan weasel with animals of the family Mustelidae in Japan, Europe and the United States, we found that the Taiwan weasel is a close relative of the Japanese least weasel. The diversion is estimated to have taken place about three hundred thousand years ago.

A petite carnivore

Until now, reported sightings of the Taiwan weasel have mostly been at high mountain areas 2,500 meters [8,250 ft] above sea level. Since there are almost no previous records of the Taiwan weasel, it can be inferred that the species is small in number.

Most of the recorded sightings occurred between June and September. Whether this is the period of proliferation following the mating season of the species requires further investigation. A Taiwan weasel was once kept in a laboratory at Tunghai University, where it was monitored twenty-four hours a day for a week, in order to locate the peak time of its daily activity. Results showed that it was especially active between five and six in the morning and from four to five in the afternoon.

The Taiwan weasel's foraging habits are still unclear. Since it belongs to a carnivorous order, it is naturally a flesh-eating predatory animal.

Least weasels in England prey mainly on small rodents (gnawing animals), sometimes feeding on small birds and eggs, but seem to avoid animals of the genus Crocidura in the order Insectivora.

Small gnawing animals in Mt. Hohuan include the Formosan wood mouse (Apodemus semotus), the Taiwan vole (Microtus kikuchii), the white-belly rat (Rattus culturatus) and the harvest mouse (Micromys minutus), the first two being larger in number. We observed in the lab that the Taiwan weasel is agile in capturing smaller prey such as the Taiwan vole and Formosan wood mouse, whereas the exercise becomes more demanding when the object is the white-belly rat, which weighs over sixty grams [2.1 oz].

Endangered treasures of Taiwan

The Taiwan weasel is endemic to Taiwan and exists only in Taiwan. It evolved on our land over a long period of time and is precious to us. Its discovery serves as new proof that the high-altitude areas of Taiwan form a special environment where biological groups can be segregated to a higher degree, climatic changes are moderate, the geologic makeup is more stable and ancient vegetation grows, thus providing shelter for many animals that migrated to our land during the glacial epochs.

These animals have long lived exclusively in the mountains, resulting in decreased genetic diversification. This makes them special and rare. Therefore any change in their living environment, especially human disruption and interference, will place these animals, which lack sufficient ability to adapt to different environments, in increased danger of extinction. The Ilimode Island feral cat in Okinawa, Japan, and the Formosan landlocked salmon are examples of this.

The ecosystem of the alpine areas of Taiwan possesses the natural conditions for genetic segregation and is an important asset for wildlife preservation and research. It is also deeply affected by human exploitation and activities.

All of the fourteen mammals listed as endangered and rare in Taiwan wildlife laws, except for the Formosan flying fox (Pteropus dasymallus formosus), live in habitats over one thousand meters [3,300 ft] above sea level. If the environment deteriorates, forcing the starting height of their range to be pushed up five hundred meters, then their habitat will lessen by eight thousand square kilometers. This leaves less than ten thousand square kilometers in which these animals can move about. Compounding the problem is the need of carnivores for large foraging areas.

The Taiwan high mountain least weasel survived the vicissitudes of the glacial epochs, but it might not be able to sustain the destruction of the montane areas brought about by the development of agriculture and forestry or the interference of the tourist population. These are problems that need to be addressed not just by the authorities, but by every person living in this land.