Butterflies that have bright colors and bold patterns can often outrun the birds that try to prey on them. A new study reveals that birds quickly learn to avoid flashy butterflies that have managed to evade them in the past, as well as butterflies that have a similar appearance.
Based on experiments, the researchers discovered that wild birds could remember the wing patterns of artificial butterflies that dodged their attacks, as well as those that had a foul flavor. In follow-up tests, the birds ignored these butterflies, as well as their lookalikes.
The experts were surprised to find that the birds learned to avoid the speedy butterflies more quickly than the ones with a foul taste. This finding indicates that being hard to catch may deter predators as effectively as chemical defenses.
Study co-author Keith Willmott is ths curator and director of the McGuire Center for Lepidoptera and Biodiversity at the Florida Museum of Natural History.
“There’s a common idea that being distasteful is one of the best kinds of defense to have, but at least in this experiment, that didn’t prove to be the case,” said Willmott.
The study provides strong evidence to support the idea of evasive mimicry, a strategy in which animals protect themselves from predators by matching the colors or patterns of agile relatives.
Most research on warning coloration has focused on species with chemical defenses and those that mimic them. For example, monarch butterflies have orange and black wing patterns that signal bad-tasting toxins. After eating a monarch, predators tend to avoid them, along with similar-looking butterflies.
A growing collection of studies suggest that a flashy exterior can also indicate that an animal has speed. Other species evolve imitations of these “racing stripes.”
“When many species share the same color pattern, they’re better able to educate predators to avoid them,” said Willmott. “The more species that share it, the better.”
Willmott studied a group of fast-flying tropical butterflies known as Adelpha. He found that dozens of Adelpha species looked virtually the same. He set out to determine whether evasive mimicry could explain why so many species of Adelpha look alike.
“It was always mysterious to me,” said Willmott. “Species whose upper wings looked incredibly similar were distantly related, and we started to see cases where even subspecies of multiple species suddenly developed very unique color patterns. Really, the only way you can explain that is through mimicry.”
The researchers designed an experiment to test whether potential examples of evasive mimicry in Adelpha could be the result of natural selection. They discovered that birds learned to connect a particular wing pattern with the negative experience of distastefulness or escape.
The birds strongly avoided the butterfly they had learned to associate with fast flight or a bitter taste, and often avoided butterflies that shared a similar color or pattern.
The study provides evidence that avoiding colorful prey is a learned behavior among birds. “This potentially explains many cases of apparent mimicry that lacked evidence of chemical defense.”
The research is published in the journal Proceedings of the Royal Society B.
By Chrissy Sexton, Earth.com Staff Writer