Courtesy of Christopher V. Anderson
Chameleons, such as this Chamaeleo calyptratus, feed by way of ballistic tongue projection, which launches their tongues at prey with a rapid burst of speed. Cold temperatures do not slow their tongues down, allowing chameleons to catch meals even when the temperature drops.
Chameleons, such as this Chamaeleo calyptratus, feed by way of ballistic tongue projection, which launches their tongues at prey with a rapid burst of speed. Cold temperatures do not slow their tongues down, allowing chameleons to catch meals even when the temperature drops. Courtesy of Christopher V. Anderson
A new study shows how chameleons manage to get a good meal even when it's cold outside.
Why should cold make a difference? Because cold-blooded animals like lizards have a problem when the temperature drops. Their muscles don't work as well.
But because of the way they shoot their tongues out to catch an insect, veiled chameleons can continue feeding — even when moving around becomes a problem.
"Chameleons have a very effective prey detection mechanism," says Christopher V. Anderson, a graduate student in biology at the University of South Florida and author of the new study. Once they detect their prey, they use what's called an elastically powered movement to extend their tongues toward their meal. It's like pulling back the string of a bow.
Once the chameleon stores enough elastic energy in its tongue, it releases it, much like an archer releases an arrow, and the tongue flies toward the target. Chameleons have to be good shots, because once the elastic tension is released, there's no way to adjust the tongue's trajectory.
Don't worry about chameleons getting enough to eat so long as an incautious grasshopper wanders by. "Chameleons are very accurate," says Anderson. They usually hit their targets.
When the temperature is cold, and their muscles don't work as well, it may take the chameleons longer to pull back the bowstring, so to speak. But once the elastic power is released, the tongue flies out at just about the same speed regardless of temperature.
Retrieving the tongue back in is another matter. As the slow-motion video shows, the tongue retraction is much slower when the temperature goes down, because this is a non-elastic movement. Not so slow that their prey escapes, says Anderson, but slower.
The new research appears in this week's edition of the journal PNAS.