Scientists have discovered a living thermometer in the Arizona desert in the form of a lizard which changes color as the temperature rises and falls, according to the New Scientist magazine.
The male striped tree lizard (Urosaurus ornatus) paradoxically turns bright blue in the heat, but is green when it is cold.
The lizard was already known to change color, but it took scientists from Hood College, Frederick, Md., to realize that its hue changes were linked to temperature.
They found that at a comparatively cool 82 degrees F. the lizard was a dull green, but as the heat increased it turned turquoise at first and was cobalt blue by the time the thermometer hit 96 degrees.
Randall Morrison from Hood College believes the lizard develops its garish blue to attract mates and ward off rivals, while its green incarnation helps to disguise it from predators when it is cold and sluggish. "When it's cool, these animals can barely move at all and the green patches help them remain inconspicuous," says Mr. Morrison. In the heat of the day "the lizards are displaying like crazy, but because it's hot they can run away fast if danger threatens," he says.