These amazing butterflies flew 2,600 miles across the Atlantic Ocean without stopping

Gerard Talavera was walking on a beach in French Guiana in October 2013 when he came across a sight that stopped him in his tracks: about ten butterflies flying around with their wings torn off.

These weren’t just any butterflies. They were painted ladies (Vanessa Cardui), a striking orange, black and white species that is common throughout the world, but not usually found in South America. He wondered how the insects traveled so far out of their typical range.

Painted ladies regularly migrate up to 9,000 miles from Europe to sub-Saharan Africa. But on that journey, they stop along the way to rest and refuel. Reaching South America would require crossing the Atlantic Ocean over and over again.

Talavera, an entomologist at the Botanical Institute of Barcelona, ​​and his colleagues have spent the past decade investigating this question. And now, they think they may have the answer.

The butterflies likely made the 2,600-mile journey across the Atlantic from West Africa with the help of favorable wind conditions, researchers report Tuesday in the journal. Nature Communications.

“This is a great piece of biological detective work,” says David Lohman, an evolutionary ecologist at the City College of New York, who was not involved in the study. New York TimesMonique Brouillette.

Although migratory insects are numerous, they are difficult for scientists to track. Researchers can’t fit tracking devices like they do with other creatures because the device is often too big and too heavy for the insects’ small, light bodies to carry. They can use radar, but only for monitoring specific regions.

Instead, scientists have historically relied on the observations of citizen scientists to piece together insect migratory routes. But this method is not perfect and still largely depends on educated guesses.

To understand how the painted ladies ended up in French Guiana, researchers approached the question from many angles. They looked at weather records for the weeks before the butterflies arrived and saw that wind conditions could have supported a journey from Africa to South America.

They also sequenced the butterflies’ genomes and learned that they were relatives of insects from Africa and Europe, which helped them rule out the possibility that immigrants had flown in from North America. In addition, they analyzed isotopes in the wings of the butterflies, which could indicate their area of ​​origin – this suggested that they were born in Western Europe and West Africa.

Providing another line of evidence, the team sequenced the DNA of pollen grains attached to the butterflies’ bodies. This allowed them to identify the plants the creatures had recently visited—Guiera senegalensis AND Ziziphus spina-christitwo species of shrubs that flower only at the end of the West African rainy season.

Taken together, their discovery strongly suggests that painted ladies flew across the Atlantic Ocean, a feat never before recorded.

“The combination of these techniques is really helping and taking us to places we couldn’t go before,” says Talavera. National GeographicJason Bittel is.

Wind was a particularly important factor in the butterflies’ journey, which scientists estimate took between five and eight days. The same air currents – known as the Saharan Air Layer – are responsible for blowing dust from Africa’s Sahara Desert into South America, where it helps fertilize the Amazon River Basin. Sometimes, the dust blows as far as Florida, where it can temporarily keep hurricanes at bay.

Now, scientists are learning that the Saharan Air Layer may also be important to insects.

“Butterflies could have completed this flight only by using a strategy of alternating between active flight, which is energetically costly, and wind gliding,” says study co-author Eric Toro-Delgado, a biologist at the Institute for Evolutionary Biology. in Spain. a statement. “We estimate that without wind, the butterflies could have flown a maximum of 780 km [485 miles] before they use up all their fat and, therefore, their energy.”