Chameleons
Use Colorful Language to Communicate: Chameleons' Body Regions Are 'Billboards'
for Different Types of Information
 |
| Chameleon calyptratus |
Dec.
11, 2013 — To protect themselves, some animals rapidly change color when their
environments change, but chameleons change colors in unusual ways when they
interact with other chameleons. Arizona State University researchers have
discovered that these color changes don't happen "out-of-the-blue" --
instead, they convey different types of information during important social
interactions. For example, when male chameleons challenge each other for
territory or a female, their coloring becomes brighter and much more intense.
Males that display brighter stripes when they are aggressive are more likely to
approach their opponent, and those that achieve brighter head colors are more
likely to win fights. Also, how quickly their heads change color is an
important predictor of which chameleon will win a skirmish. The results of the
study are published online today in the journal Biology Letters.
Russell
Ligon, a doctoral candidate in ASU's School of Life Sciences, and Kevin McGraw,
an associate professor in the school, used photographic and mathematical
modeling tools in new ways to study how the color change of veiled chameleons (Chameleon
calyptratus) relates to aggressive behavior. They studied the distance, maximum
brightness and speed of color change of 28 different patches across the
chameleons' bodies.
"We
found that the stripes, which are most apparent when chameleons display their
bodies laterally to their opponents, predict the likelihood that a chameleon
will follow up with an actual approach," said Ligon. "In addition,
head coloration -- specifically brightness and speed of color change --
predicted which was lizard was going to win."
Chameleons
typically have resting colors that range from brown to green, with hints of
yellow, but each chameleon has unique markings. During a contest, the lizards
show bright yellows, oranges, greens and turquoises. Interestingly, when the chameleons
showed-off their stripes from a distance and followed that display with a
"head-on" approach before combat, the important color signals on the
striped parts of the body and head were accentuated.
"By
using bright color signals and drastically changing their physical appearance,
the chameleons' bodies become almost like a billboard -- the winner of a fight
is often decided before they actually make physical contact," Ligon said.
"The winner is the one that causes its opponent to retreat. While sometimes
they do engage in physical combat, these contests are very short -- five to 15
seconds. More often than not, their color displays end the contest before they
even get started."
This
is the first study of its kind. The research team took pictures of color
standards and estimated the sensitivity of different photoreceptors in their
cameras. Then, they used information on the physiology and sensitivity of the
photoreceptors of chameleons, and were able to measure the colors actually seen
by the lizards. Though this method has previously been used to quantify static
(unchanging) coloration, this study is the first to quantify rapid color change
while incorporating the visual sensitivities of the animals under study.
There
are approximately 160 species of chameleons in the world. Veiled chameleons
(Chameleon calyptratus) are native to the Arabian Peninsula -- specifically
Yemen and Saudi Arabia. They are omnivorous and live essentially solitary lives
except when mating. Many chameleons are at great risk, as destruction of their
habitats is occurring at alarming rates.
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