Government bureau mulls over measures to protect migratory butterflies from traffic

This article was published by the Taiwan Journal on March 30, 2007. It reports that the Taiwan Area National Freeway Bureau plans to implement several measures to protect migratory butterflies from traffic.

Among these measures is to close one lane of a major highway during a national holiday. Another is to install ultraviolet lights under the bridges of national highways, which will guide purple crow butterflies to pass under the bridges and reduce the possibility of them being dragged under the wheels of oncoming vehicles on the highways. Finally, the bureau plans to set up a safety net, about 20 meters long and 2.5 meters tall, along the embankment sections of the bridges of national highways, so that the butterflies will be forced to fly over the highways at a higher altitude.

According to the Butterfly Conservation Society of Taiwan, purple crow butterflies live in the valleys of southern Taiwan during the wintertime, mainly in the Maolin area of Kaohsiung County and the Dawu area of Pingtung County. These butterflies migrate from the south to central Taiwan, then head north around the Spring Equinox. As they pass across west-central Taiwan's Yunlin County, the east-west direction of the area's highway becomes a barrier to them. A lot of butterflies are hit by cars.

According to the Butterfly Conservation Society of Taiwan, the high season for purple crow butterflies to migrate in huge swarms through west-central Taiwan is from mid-March to mid-April. For example, on April 3, 2005, more than 1 million butterflies were observed flying over Yunlin County. Although there are no exact figures to show how many butterflies have been killed when they flew over the area's highway, members of the Butterfly Conservation Society of Taiwan once found 50 dead butterflies within a distance of 100 meters.

According to the Taiwan Area National Freeway Bureau, if more than 2,000 butterflies per minute are found flying over the highway, then it will close off the 600-meter outer lane between kilometre markets 251.7 and 252.3. Such close-off is likely to take place during the Tome-Sweeping Festival from April 5 to 8. This and other aforementioned measures are advocated by the Butterfly Conservation Society of Tawian and the I-Shou University's Department of Civic and Ecological engineering, in a cooperative effort between the public and private sectors to help protect migratory butterflies during their trip to Taiwan.

Meanwhile, in the interest of road safety, drivers are urged to maintain a normal speed when they see the butterflies, instead of suddenly slowing down to watch the insects.