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Earth Notes: Nature's Flashy Colors

A male and a female cardinal sit in a tree, their backs to each other.
Mary Ellen St. John
/
Creative Commons
A male and a female northern cardinal sit in a tree.

All kinds of animals use conspicuous colors, from flashy reds to startling yellows and oranges. It’s a quirk of evolution that started around 150 million years ago, according to recent research from biologists at the University of Arizona.

By this time, flowers and fruits were already using color to put on beautiful displays to attract pollinators and find ways to spread their seeds. But in animals, bright colors appeared first as a warning signal, especially in snakes and amphibians.

In Arizona, the red-yellow-black pattern of the venomous coral snake is a good example. The mountain kingsnake mimics those colors; it’s not venomous but would like hungry predators to think so.

Curiously, some animals that use color as a warning don’t have color vision themselves.. or even eyes! They don’t need to see their own patterns to warn off anyone who thinks they might be a good snack.

It’s different with sexual signals, that is, colors designed to attract a potential mate. Around 100 million years ago there was an explosion in birds, lizards and ocean animals like ray-finned fishes using color this way. These animals are active during the day when they can see one another.

Think about an ordinary day for a female cardinal. She might spot a tasty fruit by its deep red color, startle back from the even more vivid red of a snake in the underbrush, and then draw closer to a potential mate to inspect his snazzy red coat. That’s a lot to learn from a single color!

And the world is ablaze with those kinds of signals: useful information transmitted through beauty.

This Earth Note was written by Melissa Sevigny and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.
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