Seeing red

Natural History, May, 2004 by Stephan Reebs

Stroll into a pet shop, and you'll find a host of colorful cages and toys for the rodent in your life. The colors, of course, are designed to appeal to (human) buyers, but it turns out that colors affect the animals as well. A recent study by Chris M. Sherwin and Elizabeth R Glen, both behavioral biologists at the University of Bristol in England, suggests that mice are discombobulated by red.

Sherwin and Glen raised mice in "home cages" painted black, white, red, or green. Then they placed the mice in two test environments, each with a choice of places to go, and clocked the time the mice spent in each place. In one environment, the mice could enter one of four "preference cages," each painted the color of one of the home cages. In the second environment, a standard test of anxiety levels, they could enter either the walled or the wide-open arms of a cross-shaped maze.

Results: no matter which color their home cages had been painted, the animals spent the least time in the red preference cage. And the animals raised in red home cages spent the least amount of time in the open, unprotected arras of the maze. Conclusion: red makes mice nervous.

You probably wouldn't feel too happy in a living room with bright red walls, but Sherwin and Glen are surprised that mice have a similar reaction. One possible trigger for the mice's distress is that red is often displayed on the body of toxic species, asa warning to leave them alone. ("Cage colour preferences and effects of home cage colour on anxiety in laboratory mice," Animal Behaviour 66:1085-92, December 2003)