Page 21 - Chameleon

Impressing, Repelling

“The female will react, depending on whether or not she’s available,” Mil-
inkovitch says. If she already has the sperm of another male in her repro-
ductive tracks, he says, “then she’s going to become very dark, and very
aggressive.”
Males can be violent, he says, so it’s important that females avoid them
if they have no need for insemination. If the female is available she won’t
show much color and instead remains a greenish-brown, Milinkovitch
says, indicating submission.
Stuart-Fox believes that changing color may serve yet another, albeit poor-
ly-researched, function: Helping chameleons regulate their body tempera-
ture. This trait is widespread among lizards—in a 2016 study, she showed
that bearded dragons can alter their skin color based on temperature—and
so it’s unlikely that chameleons wouldn’t also have this ability, she says.
Chameleons are ectotherms, she says, and so they can’t retain heat gener-
ated from their metabolism. Instead, they have to warm up using the sun.
(That’s why you see lizards basking on rocks in the early morning when it’s
cold).
Darker colors absorb more light, and chameleons have likely evolved to
capitalize on this principle, she says. When it’s cold and the sun is up, they
wash themselves with melanin to darken and thus accelerate warming—
unless the color makes them stand out, that is.
The ability to change color first likely evolved in chameleons for camou-
flage, Stuart-Fox says, but the talent now satisfies a wide range of these
animals’ needs, like temperature control.
In some cases, the talent satisfies multiple needs at once. In 2003, Stu-
art-Fox came across Smith's dwarf chameleon basking on a dark-colored
flower stalk while doing field work in South Africa. “It’s perfectly camou-
flaged,” she says, while also able to “absorb maximum sun.”
“I just think that animals never cease to surprise us in how they can achieve
multiple things at once and get the best of all worlds.”

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