Metachromatism

All lizards are ectotherms, animals who can’t regulate their body temperature internally. Lizards have to thermoregulate by moving into the sun to warm up and back into the shade to cool down. One way you can know if it’s warm enough for lizards is to touch the rocks and logs they bask on. If it’s warm to the touch to you, its warm enough for them.

Sometimes, lizards may still come out from their refuges even when it isn’t fully warm outside yet. At this emergence lizards including the western fence lizard, Sceloporus occidentalis, you’re looking for below, may appear black in color.

This phenomena is known as metachromatism. Many species of lizards change color due to the temperature. The darker color when they are cooler allows them to absorbs more heat from the sun while their lighter coloration reflects solar radiation.

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