Shimmer and shine may help prey sabotage predators’ aim

Computer game for birds shows the confusing side of iridescent coloring

a greenbottle fly

SHIMMER FOR SAFETY  That lovely iridescence on a greenbottle fly and myriad other animals might offer a bit of protection from predators.

Charles R Berenguer Jr/iNaturalist.org (CC BY-NC)

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

PECK THAT DOT In a targeting test, birds had to peck a moving circle 20 millimeters in diameter that shifted colors and brightness (example shown in this sequence) as it scooted across a computer screen. Courtesy of Tom Pike
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.

Susan Milius

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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