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Bureau acts to safeguard butterflies

A milkweed butterfly rests on the No.9 Highway between Chihpen Township and Taimali Township yesterday. PHOTO COURTESY OF CHAO JEN-FANG

As large numbers of milkweed butterflies migrate from the south of Taiwan to the north at this time of year, the Taiwan Area National Freeway Bureau has taken several measures to protect the indigenous species.

Bureau Director-General Lee Tai-ming (李泰明) said yesterday that the majority of the butterflies were expected to fly across the Linnei (林內) section of the Formosa Freeway (Freeway No. 3) in Yunlin County between 9am and 12pm from tomorrow until next Saturday.

He said the bureau would close the northbound section between the 251km and 253km markers on the Formosa Freeway -- 2km in length -- when the number of butterflies reaches 500 per minute, adding that the measure would be executed within two hours of the instruction being given.

Meanwhile, a stretch of safety net -- 4m in height and 400m in length -- has been installed on the right side of the road near the same location so that the butterflies are forced to fly above the traffic flow.

The bureau has also grown a total of 500 trees west of the Chinshui River (清水溪) in Nantou County to act as "natural safety net" for the butterflies.

Four hundred sets of florescent lamps have been installed under the overpass to guide the passage of the butterflies.

At the Tai-an Service Area (泰安休息站) of the Sun Yat-sen Freeway (Freeway No.1) and the Baihe Service Area (白河休息站) of the Formosa Freeway, the bureau has grown a large quantity of host plants and nectar plants as food for the butterflies.

The bureau's estimates show the measures cost approximately NT$2.5 million (US$83,000).

The bureau started taking proactive action to protect the milkweed butterflies last year.

However, the ultraviolet light the bureau used to try to lure the butterflies to fly underneath the elevated road proved to be ineffective. Also, the safety net last year was only 90m in length and 3.5m in height and the northbound lane was only closed when butterfly numbers topped 2,000 per minute.

Jhan Jia-long (詹家龍), a researcher at the Butterfly Conservation Society of Taiwan, said overall the measures taken last year had helped lower the mortality rate of the milkweed butterflies between 1 percent and 10 percent.

Jhan also said based on statistics collected between March 13 and Saturday, the mortality rate could potentially drop further to 0.01 percent.

"The focus this year is to experiment with ways to increase the number of butterflies flying underneath the elevated road," he said.
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