Speed Limits Could Save Rarest Dragonfly


SACRAMENTO, Calif. — Slow down, drivers. You could save America's rarest dragonfly.

We've all had insects smash into our windshield when driving. For the airlines, it's a major problem! They're losing tons of money.

The Hine's emerald dragonfly is the only dragonfly on the federal endangered species list. The insect's largest remaining population lives in Door County, Wisconsin, where sandy beaches and cherry and apple orchards draw tourists from Green Bay and beyond.

A 2003 study found these summer drivers kill about 3,300 Hine's emerald dragonflies each year, said Amber Furness, a University of South Dakota graduate student. No one knows exactly how many Hine's emerald dragonflies are left, but there are at least 10,000 in Door County and up to 3,000 in the Chicago region. [Dazzling Photos of Dew-Covered Dragonflies & Other Insects]

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Door County has posted two dragonfly warning-signs on roads near critical habitat areas. But can drivers really safely avoid a dragonfly at highway speeds, or even spot one from inside a car?

Searching for a better solution, the South Dakota researchers decided to see if dragonfly death rates were linked with speed.

Furness, a conservation biologist working with USD professor Daniel Soluk, mounted GoPro cameras on a pickup truck and drove the Door County roads in 2012 and 2013, varying her speed from 15 mph (24 km/h) to 55 mph (88 km/h) in increments of 10 mph (16 km/h). The cameras picked up each dragonfly's position before impact. Every time Furness hit a dragonfly, she tried to collect the carcass and verify the kill (a screen kept the insects out of the truck grill.)

At speeds below 35 mph (56 km/h), Hine's emerald dragonflies — and other kinds of dragonflies — survive their tumble over the hood, and fly away to live another day, Furness found. Faster speeds kill, according to Furness' research, presented here Thursday (Aug. 14) at the Ecological Society of America's annual meeting. The dragonflies are either killed on impact or they suffer severe shock and fall to the ground, and are run over by a second vehicle.

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