Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=209680
Story Retrieval Date: 9/30/2014 2:55:58 PM CST

Top Stories
Features
MIGRATION03

J.M. Garg

The Painted Lady (Vanessa cardui)


Are we there yet?: Radar and citizen scientists help unravel Painted Lady migration mystery

by Matt Rhodes
Oct 25, 2012


MIGRATE15

Matt Rhodes/MEDILL

Get close to nature. Dodge the butterflies in the Butterfly Haven at the Peggy Notebaert Museum in Chicago.

MIGRATE09

Matt Rhodes/MEDILL

Steven Sullivan, senior curator of Urban Ecology at the Peggy Notebaert Museum in Chicago, compares the migration patterns of the Monarch butterfly to the Painted Lady.

Imagine embarking on a journey so extreme that it would span not only your own lifetime, but also five generations hence. A trip so long, in other words, that your great, great, great, great grandchild would complete the voyage that you originally set out on -- long after you’re dead and gone.

Sound daunting?

Well, a massive new science study has detailed how the Painted Lady butterfly does just that – every year. Thanks to one of the largest citizen science projects ever conducted combined with new radar techniques, scientists have successfully tracked the migration pattern of the Painted Lady, thus unraveling a longstanding scientific mystery.

The findings, reported in the journal Ecography last week, reveal that painted ladies make a 9,000 mile round trip from North Africa to the Arctic Circle.

“The extent of the annual journey undertaken by the Painted Lady butterfly is astonishing,” said Richard Fox, Surveys Manager at Butterfly Conservation and one of the paper’s authors. Scientists had previously known that theyarrive in the United Kingdom from Europe to procreate, but weren’t clear on where they go as the weather gets colder. One theory, known as the “Pied Piper hypothesis,” suggested that the butterflies simply die out.
But instead, it turns out that when autumn comes they move high into the atmosphere and head south from Britain.

Researchers found the answer by using new radar-tracking techniques, and analyzing sightings from 60,000 volunteer observers across Britain and Europe.

“Clearly, citizen science was incredibly important in this discovery,” Steven Sullivan, Senior Curator of Urban Ecology at the Peggy Notebaert Nature Museum in Chicago. “This is one of the greatest aspects of the Internet: taking data from scientists and citizen scientists alike and using them synergistically to realize new discoveries.”

“They’ve been able to solve one more piece in this insect migration puzzle,” Sullivan said of the new findings.

When they get ready to leave Britain and head south, the painted ladies use the jet stream as a kind of high-altitude highway traveling at around 30 mph, 1,640 feet up in the sky, the study found.

Because they are in fast-moving air, the butterflies are able to travel at double their usual speed without risking damage to their delicate wings.

“Since the Painted Lady is traveling at the same rate of speed as the air molecules in the jet stream, they are essentially moving at zero mph, even though relative to the ground, they are traveling at 30 mph,” Notebaert’s Sullivan explained. “So they’re not experiencing the same type of wind resistance that they would if you whipped them through the air at 30 mph on the surface.”

In the spring of 2009, new radar systems tracked 11 million U.K.-bound painted ladies in the spring, and 26 million outbound in the fall, thus showing that the British Isles served as a fertile reproduction pit-stop for the butterflies.

The average life span of the Painted Lady is only about two to four weeks, so the 9,000 mile journey is trans-generational as well as intercontinental.

“This tiny creature, weighing less than a gram with a brain the size of a pinhead and no opportunity to learn from older, experienced individuals, undertakes an epic intercontinental migration.” The incredible transit the painted ladies make is almost double the length of the famed migration of the Monarch butterfly, which makes an annual round trip from Canada to Mexico. The monarch’s trip similarly spans three to four generations (their average life span ranges from two to eight weeks).

Typically, the third generation of migrating Monarchs stop in Illinois on their way to Canada, Sullivan said.

“It’s simply amazing that these distant relatives know exactly where to go without having ever experienced these locations for themselves.”