Presented with a model of a predator bird, the fiscal shrike, chameleons colour-matched their backgrounds much more closely than with a model of a snake, see below (Image: Devi Stuart-Fox) The venomous Boomslang has poorer colour vision than the shrike, and so produced less vivid changes in the chameleons’ camouflage (Image: Devi Stuart-Fox)

Chameleons’ mastery of camouflage goes further than anyone expected – it seems they can fine-tune their colour changes to the visual systems of specific predators.


Devi Stuart-Fox at the University of Melbourne, Australia, and colleagues studied the Smith’s dwarf chameleon (Bradypodion taeniabronchum), which lives in South Africa.

This critically endangered chameleon can alter its colour palette in milliseconds, either for camouflage or for social signalling.

The team captured eight males and eight females of the species. They placed them on a branch and presented them with realistic models of two of their biggest predators: the fiscal shrike (a bird that impales chameleons on thorns before eating them) and a venomous tree snake called the boomslang.

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Bird threat

Using a spectrometer, the team took readings of the colour shades and brightness of the background and the chameleon. Then, after the chameleon had spotted the model predator and changed colour, they took another set of readings.

The chameleons colour-matched their backgrounds much more closely when presented with a bird than a snake, the team found.

However, when the team modelled the visual systems of both predators, they found that the chameleon still appeared better camouflaged to the snake than the bird, thanks to the snake’s relatively poor colour vision. In the presence of a snake, it seems, the chameleons just don’t have to try as hard.

Subtle changes

The researchers noticed that the chameleons were also consistently paler, compared with their background, when presented with the tree snake.

“This is probably because while birds usually approach from above, putting the chameleon against a dark background, snakes usually approach from below, putting it against a background of a light, bright sky,” says Stuart-Fox.

Other animals can adjust their defensive behaviour or appearance in response to different predators.

For instance, the ground squirrel pumps more hot, infrared emitting blood into its tail when it spots an infra-red sensing rattlesnake. But this is the first time anyone has observed an animal modifying that change to best avoid being seen.

Journal reference: Biology Letters (DOI: 10.1098/rsbl.2008.0173)