The flight of the monarch and TxDOT’s efforts to make it safer
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The flight of the monarch and TxDOT’s efforts to make it safer

Millions of butterflies migrate through Texas in a treacherous journey

By Ryan LaFontaine

AUSTIN — The official insect of Texas makes a treacherous trek each year through the state, and the Texas Department of Transportation is working to make the journey a little safer.

Every fall, millions of monarch butterflies make an extraordinary journey to Mexico from North American breeding grounds, entering Texas around Wichita Falls, weaving through the Hill Country and eventually crossing the border near Eagle Pass and Del Rio.

Millions will eventually make it to Mexico, but many will be killed after colliding with vehicles while flying low across Texas highways.

TxDOT partnered with the Texas A&M Transportation Institute and completed a 2-year study to determine the location and extent of monarch deaths on Texas roadways. The study looked at mitigation strategies that TxDOT could implement to reduce collisions with traffic.

"The study identified nearly a dozen hot spots, where monarchs were being killed by vehicles," said John Maresh, TxDOT environmental specialist.

The monarch is considered a "candidate species," which means it is currently being reviewed to determine whether it warrants listing under the Endangered Species Act.

"Not only is this a conservation issue, but it’s also a safety issue," Maresh said. "If you’ve ever driven through a cloud of monarchs, it can be unnerving. There are thousands of them crossing the road all at once."

TxDOT plans to install "monarch flight diverters" next to highways along the migration route. The diverters are netting that will force the monarch to fly higher above the road and avoid traffic. Maresh said plans are to have several test deflectors installed before the fall migration.

In the spring and summer, monarchs migrate north from Mexico, laying eggs on milkweed plants during their journey. The eggs produce caterpillars, which become winged butterflies that move farther north, repeating the cycle over multiple generations until they reach Canada. These breeding monarchs have a lifespan of two to five weeks.

However, the final generation of monarchs — born in late summer — can live about eight months, allowing them to make the flight to Mexico, hibernate for the winter and start the breeding cycle and northerly migration all over again the following spring.

Did you know?

  • At least 90% of all monarch butterflies migrate through Texas.
  • These amazing butterflies have tiny bodies, tiny brains and flimsy, orange and black wings, and yet they travel more than 2,500 miles every year.
  • No single butterfly ever completes the entire migration cycle.
  • Monarchs will instinctively find the same pine tree in Mexico for hibernation that their ancestors used the year before.
  • Monarchs have declined about 82% over the last 23 years.

According to the U.S. Fish and Wildlife Service, more than 45 energy and transmission companies and state departments of transportation are voluntarily committing time and funding to carry out monarch butterfly-friendly management practices on millions of acres in rights of way.