Some Chameleons Flash Their Colors to Get a Date

What more dramatic type of visual communication is there than being able to change color? The two most well known animals to utilize this strategy to the extreme are cephalopods (octopus and relatives) and, of course, chameleons. These groups use chromatophores, which are pigment-containing cells in the dermis, to change color. Most animals with this capability use hormones to control the color change. The evolution of chromatophores gives these two groups more direct control over this technique. A chameleon can change its color in milliseconds! Wouldn’t it be useful to be able to disappear into the background when the one person in the room that you don’t want to see you starts to walk your way? Well that is what most people think that chameleons use their color changing abilities to do: camouflage. However, a recent study provides evidence that, at least for the African Dwarf Chameleons, the ability to change color is just a strategy to pick up the ladies.

Devi Stuart-Fox and Adnan Moussalli’s 2008 study, “Selection for Social Signaling Drives the Evolution of Chameleon Colour Change”, used 21 lineages of African Dwarf Chameleons, Bradypodion spp., to test whether the evolution of color change is driven by crypsis (camouflage) or social signaling. They collected data to analyze whether the color change was positively correlated to the chameleons’ background or to the chameleons’ conspicuousness. They measured and quantified coloration, color change reflectance and also took into account what the major predators, mainly birds, would see when the chameleons put on their red carpet best. As we have learned in class in the many many lectures about birds, birds are UV sensitive, (and so are chameleons). Results? The greatest variation of color change was observed in inter-species situations rather than in predator response situations. After all the statistical math was tabulated, they found a positive relationship between color change and conspicuousness and no evidence that color change was related to crypsis. Males use submissive species-specific color signals when they lose a dominance joust with another male and when the female he is courting refuses his advances. The females use light and dark aggressive displays to tell the males to get lost. Surprisingly, the females in this genera do not use this strategy to convey reproductive status as has been shown with other chameleon groups.

Here is a cool link to a site that has some funny cartoons (for sale if you are interested) focusing on chameleon communication:

http://www.cartoonstock.com/directory/c/chameleons.asp

The ones I would’ve liked to post are the 6^th, 7^th and 9^th ones down. The first five don’t even look like chameleons and look like a five year old trying to drawn some unknown generic species of dinosaur and the 9^th one down…what? I’m not sure how this one relates. I went on a bit of a tangent here, my apologies. So, for your pleasure and enjoyment feel free to check it out. I thought it was amusing.

There is always a trade off between being flashy and blending into the surroundings. Although these chameleons aren’t going for the whole master of disguise technique, they have the ability to quickly change color to get their point across, but are not stuck with a flashing old run down diner sign that reads “good eats.”

posted by: Jess Bouchard (1)