(CN) — Monarch butterflies are known for their classic black, white and orange colors — and for having the most evolved migration pattern among their species. They travel up to 2,500 miles from their breeding grounds across the U.S. and Canada to hibernation sites in Mexico, and these iconic insects’ ability to traverse a continent has kept scientists fascinated for years.
Now, research published in PLoS ONE on Wednesday indicates that the more white spots a monarch butterfly has, the more successful it will be at migrating. Lead study author Andy Davis, assistant researcher at the University of Georgia’s Odum School of Ecology, and his team studied approximately 400 images of monarch butterflies at various stages of migration. The proportions of color were then analyzed, and the results were a bit of a shock.
“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,” Davis said in a press release. “It’s the white spots that seem to be the difference maker.”
The team found the butterflies successful in their migration had 3% more white and 3% less black coloring. The team also found that monarchs have significantly larger white spots than their non-migratory cousins.
These findings challenge some aspects of aerodynamics. Research has long shown that dark colors on wings can make an animal more aerodynamic. Because dark colors absorb more energy from the sun, they can generate a pocket of warm air. This heat allows animals to have less wind resistance.
But monarch's white spots also seem to help them absorb less solar energy. They are exposed to heavy amounts of solar energy and solar radiation during migration, and the white protects them from the harsh rays.
“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.”
This does leave researchers concerned about rising temperatures and the insect’s ability to cope. If temperatures rise faster than the monarchs can adapt, they may not be able to make it through their migrations.
However, Davis’ previous research does act as a beacon of hope for monarch populations. In a study published last year, Davis found that monarch numbers rebound in the summer in spite of migration losses and that the population has stayed relatively stable for 25 years.
“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.”
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