The species butterflies Vanessa Cardui They venture over wide areas with their impressive migratory patterns that stretch thousands of miles — but they often travel overland, so they may stop to rest.
Scientists have found evidence that a group of these winged travelers flew more than 2,600 miles across the Atlantic Ocean without stopping, according to a new study published on June 25 in the journal Nature Communications.
The discovery solves a decade-old mystery that began when entomologist and study lead author Dr. Gerard Talavera found about 10 butterflies Vanessa Cardui on a beach in French Guiana in October 2013. The insects, which are not normally found in South America, were worn out with holes and tears in their wings.
“They looked exhausted. They couldn’t even fly very much, they kind of jumped instead of flying,” said Talavera, a senior researcher at the Spanish National Research Council at the Botanical Institute of Barcelona. “The only explanation that came to mind was that they were long-distance migrants.”
But crossing an entire ocean was unheard of for butterflies, even those as well-traveled as butterflies. Vanessa Cardui. Talavera and his colleagues needed to rule out a few factors before concluding that these butterflies accomplished what was previously considered impossible.
How far can a butterfly fly
An October 2016 study co-authored by Talavera found that butterflies Vanessa Cardui From Europe they migrate great distances of around 4,000 kilometers to sub-Saharan Africa, facing obstacles such as the Mediterranean Sea and the Sahara Desert. But even then, butterflies mostly stay on land, where they can “stop and refuel, feed on flowers and then get energy to keep going,” Talavera said.
Crossing the Atlantic would take a butterfly five to eight days Vanessa Carduidepending on different variables, as the new study points out.
Based on analysis of energy constraints, the researchers concluded that the butterflies could fly a maximum of 780 kilometers without stopping, but favorable wind conditions allowed them to complete the long journey, Talavera said.
“This is actually a record for an insect, especially a butterfly, to make such a long flight without the possibility of stopping,” said Talavera, who also leads the World Wildlife Migration Project. Vanessa Carduia global citizen science project that tracks the migratory routes of insects.
There have been other cases in which experts suspect that butterflies and other migratory insects have traveled greater distances than usual, appearing on boats, remote islands or countries where they are not normally found, Talavera said.
Researchers believe these butterflies took part in their annual migration south from Europe, but got lost when the wind blew them into the ocean, he added. The butterflies then probably took advantage of the trade winds, which blow from east to west near the Equator, until they reached land in South America.
“To be suspended in the air column at just the right height to take advantage of the trade winds is nothing short of remarkable,” said Dr. Floyd Shockley, collections manager in the entomology department at the Smithsonian National Museum of Natural History in Washington, who was not part of of the new study.
“It raises the question, have they been doing this for a long time and we never documented it because we weren’t looking for it in South America?”
The discovery of about 10 out-of-place butterflies, compared to the occasional lone individual found likely caught in storms, could be enough evidence that this was a coordinated migratory event for the group of insects, Shockley said.
Tracking a butterfly
Researchers took some crucial steps to confirm that these out-of-place butterflies actually traveled across the ocean.
First, to rule out that the insects did not travel overland from North America, the researchers analyzed their DNA, finding that it matched that of European-African populations.
Next, the team used a technique known as isotope tracking that analyzes the composition of butterflies’ wings for evidence of the types of plants they ate as caterpillars, said study co-author Dr. Megan Reich, a postdoctoral researcher. PhD at the University of Ottawa, Canada. By this method, scientists concluded that the birthplace of the butterflies was in Western Europe, North Africa or West Africa, she added.
But the real key to finding the route the butterflies took was a method first described in a September 2018 study led by Talavera that found that pollen attached to butterflies can reveal their migratory journey through the plants they fed on.
The butterflies spotted in October 2013 had pollen from two West African plants, Guiera senegalensis It is Ziziphus spina-christi. The tropical shrubs bloom from August to November, according to the study, and this flowering season coincides with the timing of the butterflies Talavera discovered in South America.
Furthermore, an analysis of meteorological data from 48 hours before the butterflies’ discovery on the beach showed it to be “exceptionally favorable for the butterflies to disperse across the Atlantic from West Africa,” the authors noted in the study.
If the insects traveled from their likely birthplace in Europe, then to Africa and South America, the butterflies’ journey could have been at least 7,000 kilometers).
“Many people think of butterflies as really fragile creatures. I think it really shows how strong and resilient they are and these incredible journeys they go on. They really shouldn’t be underestimated,” Reich said.
The researchers hope to use the same techniques to investigate the migratory patterns of other butterfly species, he added.
“This is just the first step in a long process of trying to understand why this happened and how it happened,” Shockley said.
If future research finds that the butterflies’ journey is likely a regular migratory pattern, it would be among the longest insect migrations in the world, he added.
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