Study explains why some species keep their toxicity a secret

SEOUL, May 19 (UPI) -- Often, animals warn predators of their toxicity with bright displays of color and alarming patterns. Some, however, don't divulge their defenses until the very last moment.

A moth might flash a bright red on the underside of its wing as it struggles in the beak of a bird.

New research explains this evolutionary paradox. Species that keep their poison a secret, researchers at Seoul National University found, take advantage of the complexities of the learning process.

Lanternflies are a large group of butterfly-like insects. The group includes several species that camouflage their defense mechanisms, like the production of chemicals that give the insect a bitter taste.

Researchers genetically modified a group of lantern flies to instead taste juicy sweet. Then, the researchers presented a mix of tasty and bitter lanternflies to some hungry birds.

All of the lanternflies featured a rather dull, inconspicuous appearance, but only the bitter bugs boasted a bright flash of red and white on their undersides. Researchers found the birds were quickly able to distinguish between the two bugs, despite their plain appearance.

The researchers suggest the birds' memory and learning is enhanced by the unexpected display of the information, just as a student might better remember a set of facts that are communicated in an exciting or unusual manner.

"This strategy helps the distasteful prey in two ways," Changku Kang, a grad student at SNU, said in a news release. "The predators that are sensitive to the toxins produced by the prey can quickly learn to avoid the prey. But, those rare predators that are not sensitive to the toxins have difficulty spotting the prey because if its relatively cryptic appearance."

The new research was published this week in the journal Frontiers in Ecology and Evolution.