Taiwan has taken early action to protect one of its most remarkable natural events—the migration of the Purple Crow Butterfly—by closing a section of the freeway to prevent harm to the delicate creatures. This marks the earliest implementation of butterfly protection measures on a freeway in nearly a decade, highlighting the impact of climate conditions on butterfly migration patterns.
Butterfly Migration Prompts Early Freeway Lane Closure
On March 13, 2025, the Taiwan Purple Crow Ecological Preservation Association and the Taiwan Freeway Bureau took swift action by closing a freeway lane from 8:50 a.m. to 1:30 p.m. on the northbound stretch of National Freeway No. 3, specifically between the 253 and 251-kilometer markers in Linnei, Yunlin County.
The lane closure was enacted to protect migrating Purple Crow Butterflies, which were flying in large numbers across the highway. The association reported that over 30,000 butterflies passed through the area in just one morning, with a peak traffic rate of 690 butterflies per minute at one point.
To further ensure their safety, the Freeway Bureau also set up a 1,100-meter-long protective net, which helps prevent butterflies from being caught in vehicle turbulence. The lane closure was triggered once butterfly density exceeded 250 per minute and remained in effect until numbers decreased to a safer level.
Why Is This Migration So Important?
The Purple Crow Butterfly (Euploea tulliolus) is one of the world’s most famous migratory butterflies, often compared to the Monarch Butterflies of North America. Each year, these butterflies travel from southern Taiwan to the northern forests to escape the rising temperatures of their breeding grounds.
Taiwan is home to one of the world’s two largest migratory butterfly populations. The route they take crosses National Freeway No. 3, posing a serious risk as high-speed vehicles can kill thousands of butterflies if no protective measures are taken.
For over fifteen years, Taiwan has been a global leader in butterfly conservation efforts, using freeway lane closures, protective nets, and even guiding structures to prevent butterfly fatalities.
Why Did the Migration Start Early This Year?
Experts from the Taiwan Purple Crow Ecological Preservation Association have attributed this year’s early migration to unusual weather patterns:
- Colder-than-usual winter – The winter months were colder than expected, delaying some butterfly activity.
- Rapid warming in early March – A sudden temperature increase triggered an early departure from their wintering grounds, prompting them to move north sooner than usual.
- Shifting climate trends – Climate change has been impacting migration cycles, causing variations in timing from year to year.
When Will the Peak Migration Occur?
While this freeway closure is the earliest in nearly a decade, experts predict that butterfly migration numbers will significantly increase between March 20 and the end of March.
- More freeway lane closures may be implemented in the coming weeks if butterfly traffic remains high.
- Taiwan’s Tomb Sweeping Festival (April 4-6) has traditionally been the peak migration period, but this year’s migration may reach its highest point earlier.
FAQs
Why does Taiwan close a freeway lane for butterflies?
Taiwan closes lanes to prevent migrating Purple Crow Butterflies from being killed by vehicles as they cross National Freeway No. 3.
When does the Purple Crow Butterfly migration usually happen?
The migration typically peaks in late March or early April, but this year, it started earlier than usual due to sudden weather changes.
How many butterflies migrate each year?
Hundreds of thousands of Purple Crow Butterflies migrate from southern to northern Taiwan annually.
What other conservation measures are in place?
In addition to lane closures, Taiwan has installed protective nets and guiding structures to help butterflies navigate safely.
Is climate change affecting butterfly migration?
Yes, changes in temperature and seasonal shifts have altered migration patterns, sometimes causing earlier or later migrations.
