Natures wonders: monarch migration more understood (Introduction)

by David Turell , Wednesday, June 21, 2023, 23:39 (519 days ago) @ David Turell

Monarchs with more white on their wings where more successful migrators:

https://phys.org/news/2023-06-monarchs-white-shown-aid-migration.html

"The new study, published in PLOS ONE suggests that the butterflies with more white spots are more successful at reaching their long-distance wintering destination. Although it's not yet clear how the spots aid the species' migration, it's possible that the spots change airflow patterns around their wings.

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"The monarchs with less black on their wings and more white spots were the ones that made it to their ultimate destination, nearly 3,000 miles away in south and central Mexico.

"'It's the white spots that seem to be the difference maker," Davis said.

"The only other species that came close to having the same proportion of white spots on its wing was its semi-migratory relative, the southern monarch.

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"The monarchs with less black on their wings and more white spots were the ones that made it to their ultimate destination, nearly 3,000 miles away in south and central Mexico.

"'It's the white spots that seem to be the difference maker," Davis said.

"The researchers analyzed nearly 400 wild monarch wings collected at different stages of their journey, measuring their color proportions. They found the successful migrant monarchs had about 3% less black and 3% more white on their wings.

"An additional analysis of museum specimens that included monarchs and six other butterfly species showed that the monarchs had significantly larger white spots than their nonmigratory cousins.

"The only other species that came close to having the same proportion of white spots on its wing was its semi-migratory relative, the southern monarch.

"The authors believe the butterflies' coloring is related to the amount of radiation they receive during their journey. The monarchs' longer journey means they're exposed to more sunlight. As a result, they have evolved to have more white spots.

"The amount of solar energy monarchs are receiving along their journey is extreme, especially since they fly with their wings spread open most of the time," Davis said. "After making this migration for thousands of years, they figured out a way to capitalize on that solar energy to improve their aerial efficiency."

"Davis' previous work showed that summer populations of monarchs have remained relatively stable over the past 25 years. That finding suggests that the species' population growth during the summer compensates for butterfly losses due to migration, winter weather and changing environmental factors.

"'The breeding population of monarchs seems fairly stable, so the biggest hurdles that the monarch population faces are in reaching their winter destination," Davis said. "This study allows us to further understand how monarchs are successful in reaching their destination.'"

Comment: this is still an amazing story. One migration in volves four molts and the final form knows what to do to return to home. The idea that they use sun energy is fascinating, especially if true.