Exploration : The Formation of the Maolin Butterfly Valley

The Cause and Formation of the Maolin Purple Butterfly Valley
 

In June 2003, an internationally renowned butterfly researcher, Dick Vane Wnight specifically introduced in his book, a publication of British Museum, namely “Butterfly”, of what he regarded as “An expected encounter in Taiwan in the winter of 1971.” He then listed the Maolin Purple Butterfly Valley and the Monarch Butterfly Valley in Mexico as two of the largest “Winter Migratory Butterfly Valleys” in the world. This prominently demonstrated the preciousness and the ecological uniqueness of the Maolin Purple Butterfly Valley.
 

Being an excellent geographical shelter, the Maolin Area has over a million of milkweed butterflies fly with its paragliding-like purple wings to the foot of Mt. Dawu, the so-called, “Holy Mountain” of the Rukai and Paiwan tribes for shelter over the winter. In recent years, those butterflies that flock to the Purple Butterfly Valley in every winter are all taxonomically members of the Danaidae. Approximately 80% of them are purple crow butterflies which are embedded with velvet-like, purple spots around their dark brown wings these include Euploea eunice hobsoni (Blue-branded King Crow Butterfly), Euploea tulliolous (Dwarf Crow Butterfly), Euploea sylvester swinhoei (Two-branded Crow Butterfly) and Euploea mulciber (Striped Blue Crow Butterfly). The rests are species of the Linnaeus which have scattered water blue spots on their wings.
 

The Purple Butterfly Value merely embraces Kaohsiung, Pingtung and lower elevated mountain areas of Taitung County in the southern part of Taiwan. Although the purple crow butterflies belong to the common species that are distributed throughout the low elevated mountain areas in Taichung, they are butterflies naturally incapable of enduring the cold as they originated from the tropical zone. By this fact, they are forced to migrate to the Purple Butterfly Valley every year to gain shelter from the cold east northerly wind. Purple Butterfly Valley is known for its strategic geographical position to offer such shelter. It is located on the southern part below the Tropic of Cancer below the altitudes of 500m. the nearly dried up river ditches, and the possession of stable sources of water and nectar plants (e.g. shiny bugleweed herb and Lantana camara) offer a temporary habitat for the winter migratory butterfly.

The facts that the valley opening almost faces the south and the sheltering mountains in the north make it almost impossible for the east northerly wind to make its way into the valley. Although there is sufficient fats accumulated in the bodies of these butterflies to cater for the energy needs throughout the winter, water is still required to produce a biological reaction in turning the fats to energy. Hence, adequacy in water source is also a compulsory condition for the Purple Butterfly Valley.

Reference：

http://www.svtw.org.tw/~butterfly/pruple9.htm

http://www.butterfly.org.tw/newspaper_detail.php?sn=1504
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