Flap-necked chameleons change colour to match their background

Popular culture leads us to believe that chameleons change colour to match their backgrounds, yet surprisingly, this ability has rarely been demonstrated under controlled conditions. Existing research shows that colour change is primarily used for social signalling and thermoregulation, and that chameleons revert to a generic background-matching colour for camouflage rather than tuning their colour to specific backgrounds. Here, to test the background-matching abilities of flap-necked chameleons (<i>Chamaeleo dilepis</i>), we placed them on backgrounds of various standardized colours and patterns and measured their appearance over time using models of predator vision. We found that chameleons could change their brightness to better match black backgrounds and change colour to match some hues, especially yellow. They did not match background patterns. In demonstrating that flap-necked chameleons use colour and brightness changes to facilitate camouflage, we provide further evidence supporting this function of colour change in chameleons.