A chameleon changes colour mainly to signal mood and to regulate its body temperature.

The longer version

Many reptiles shift shade slowly by moving pigment within skin cells, but chameleons add a second trick. Under their skin lies a layer of tiny crystals that reflect light, and changing the spacing between them alters which wavelengths bounce back, producing rapid shifts from green to yellow or blue.

Because the effect is optical rather than purely chemical, the change happens quickly and is controlled by the nervous system. A cold animal darkens to absorb more solar heat, while a displaying male flashes bright patterns to rivals or potential mates. Camouflage plays a smaller role than popular accounts suggest, since colour mostly tracks mood, light and temperature.

Where this entry sits

This collection gathers small surprises about mammals, reptiles, amphibians, birds, fish, insects, and the pets living alongside people. Expect odd details about senses, anatomy, and everyday behaviour that many people never notice in the animals around them. The full list sits on the Animals page, where every entry is listed in order.