Monarch butterfly: Study sheds new light on the mysterious origin, role, and benefits of white spots
Researchers from the University of Georgia may have unraveled the mystery behind the distinct spotted pattern on the wings of monarch butterflies.
The findings from a new study, published in PLOS ONE, indicate that the number of white spots on the wings of these butterflies could be linked to their ability to successfully complete their long-haul winter migration. The exact role these spots play in their migration is still unclear. However, researchers hypothesize that these spots might alter the airflow around their wings.
Andy Davis, the lead author of the study and an assistant researcher at UGA’s Odum School of Ecology, commented, “We undertook this project to learn how such a small animal can make such a successful long-distance flight.”
Davis further added, “We actually went into this thinking that monarchs with more dark wings would be more successful at migrating because dark surfaces can improve flight efficiency. But we found the opposite.”
Interestingly, monarch butterflies with a smaller proportion of black on their wings and more white spots were found to be more successful in reaching their end destination, which is nearly 3,000 miles away in the south and central regions of Mexico.
Davis remarked, “It’s the white spots that seem to be the difference maker.”
Butterfly Migration Influenced by Wing Spot Patterns
In the study, nearly 400 wings from wild monarch butterflies collected at various points of their migration were examined, revealing that the successful migrators had approximately 3% less black and 3% more white on their wings.
A subsequent analysis of museum samples encompassing monarchs and six other butterfly species revealed that migrating monarchs have noticeably larger white spots compared to their non-migratory counterparts.
Interestingly, the only species with a similar proportion of white spots was the southern monarch, a semi-migratory relative.
Solar Energy Boosts Monarch Flight
The study’s authors postulate that the butterflies’ color pattern might be connected to the amount of sunlight they absorb during their travels. Monarchs, undertaking a long journey, get more exposure to sunlight, and over time, this might have led to an evolutionary increase in their 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 added. “After making this migration for thousands of years, they figured out a way to capitalize on that solar energy to improve their aerial efficiency.”
However, with global temperatures on the rise, altering the levels of solar radiation reaching the earth’s surface, Mostafa Hassanalian, the study’s co-author and associate professor at the New Mexico Institute of Mining and Technology, believes that monarchs may need to adapt for their survival.
“With greater solar intensity, some of that aerial efficiency could go away,” Davis added. “That would be yet one more thing that is hindering the species’ fall migration to Mexico.”
Stability Observed in Monarch Breeding Populations
However, the future isn’t entirely bleak for these winged creatures.
Previous research conducted by Davis indicated that the summer populations of monarch butterflies have managed to maintain relative stability over the past quarter-century.
This suggests that the population expansion during the summer months might offset the losses experienced by the species due to migration, winter climates, and environmental changes.
“The breeding population of monarchs seems fairly stable, so the biggest hurdles that the monarch population faces are in reaching their winter destination,” Davis added. “This study allows us to further understand how monarchs are successful in reaching their destination.”
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