Shimmer and shine may help prey sabotage predators’ aim

A peck-the-bug computer game for quail shows that some of nature’s most spectacular coloring might be peacock obvious to the eye but tricky for a predator to grab.

In lab tests, it took birds almost four tries on average to nail an iridescent bug target (roughly inspired by the coloring of a greenbottle fly) as it moved across a gray screen, says Tom Pike of the University of Lincoln in England. The birds pecked similar targets without the shimmer in fewer than three tries on average. And the birds struck closer to the target center on the plain bug stand-ins than on the iridescent ones, Pike reports April 15 in Biology Letters.

This unusual test bolsters the idea that flashy, changeable coloration mig

ht offer certain animals a measure of protection from predators. Interference coloration, as it’s called, looks as if it shifts hue and flashes bright or winks to dull depending on the viewing angle and the light. Such shimmery effects have evolved in clam shrimps, orchid bees, rainbow boas, golden moles and many other animals. Biologists have proposed functions from courtship signaling and camouflage to body temperature regulation.

To test the idea that shimmering might sabotage predator aim, Pike simplified the challenge. Targets just looked like hemispheres gliding across a screen at about 150 millimeters per second. Whether real prey would prove as tricky to peck in the mosaic of backgrounds and lighting outdoors remains to be seen.