2023-08-12 17:09:08
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Here we are in a paradise of biodiversity: the island of Madagascar. Many species of animals and plants live only here, it is impossible to observe them elsewhere in the world than on this piece of land bordered by the Indian Ocean. They are said to be endemic to the island of Madagascar. Here life has therefore evolved in a vacuum, cut off from the rest of the world. And it developed in an unexpected, spectacular way, offering an explosion of shapes and colors like no other. Color is what will interest us today. Because the animal we are looking to observe is one of the few to have the extraordinary ability to change it on command. From Antananarivo, the capital, we follow the road that leads north, in search of a jewel: the primary forest of Madagascar. A primary forest is an exceptional place. Preserved from all activity, these original forests are the refuge of countless species that can live there far from the noise and polluting activities of humans. It is in this forest, for example, that the ugliest orchid in the world was discovered, Gastrodia agnicellus, whose flower looks like a gaping, slimy mouth. Or, the species Brookesia nana, a tiny chameleon barely 1 cm long, the smallest in the world! Because, in Madagascar, live almost half of the species of chameleons known on Earth. And today we have an appointment with one of them.
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Meet the giant chameleon of Madagascar
Here we are: on his tree, in the humidity of the tropical climate, a silhouette looks like a miniature dinosaur. A big lizard basks in the sun, it’s a chameleon, of the species oustalet’s fury, the giant chameleon of Madagascar! This emblematic species can measure up to 70 cm in length! It sports a color that varies from brown to green, spotted with white or yellow, and a crest runs all along its body with small jagged spikes. Pay attention to his paws. Like us, this chameleon has five fingers, but these are arranged a little differently from ours. While with us the thumb opposes the rest of the fingers to form a claw – we simply say that it is opposable, with our friend there are two fingers on one side and three fingers on the other to grip to the branches. It’s a bit like grabbing a bottle of water by placing your thumb and index finger on the same side! It may seem impractical to you, but for the chameleon, it’s only natural. Ah… a reckless butterfly is approaching. He takes a big risk, because chameleons love insects and can even gobble up birds or small rodents. Watch out, little butterfly… the chameleon, with its prominent, independent eyes that swirl in their sockets, is on the prowl. Nothing escapes him. In an instant, the tongue of the chameleon, as if mounted on springs, shoots out at full speed and melts on the butterfly. It cannot escape the attack, because this language is of an exceptional length, and its viscous end engulfs its prey. The little butterfly has already reached the depths of the lizard’s stomach. It may not advance very quickly on its branch, but for hunting, it is unbeatable.
Chameleons are fascinating animals in more ways than one. But one of their abilities has made them famous: they are able to change color. For a long time, it was believed that this super power allowed them to blend into any environment to go incognito. In short, that it was used for camouflage. But researchers have discovered that the reality is a little more complex than that. To unravel the mysteries of the color of chameleons, head to Arizona, in the United States. You will see that our extraordinary lizard has more than one trick up its sleeve…
Fighting and emotions: the hidden side of the chameleon’s color change
To better understand how and why the chameleon changes color, scientists from the University of Arizona organized a big boxing tournament between chameleons. Because chameleons are very territorial, so meeting a fellow chameleon can quickly turn into a fight. For the purposes of the experiment, the researchers tested the reactions of 10 wild chameleons during an encounter with another individual. In this case, helmeted chameleons were chosen for the experiment.
Originally from the mountains of Arabia, these chameleons have been introduced to the United States and, more precisely, to the nearby state of Florida, which is very practical! They owe their name to the bump that overhangs their head, although this characteristic is shared by many chameleons. When two helmeted chameleons meet, a strange choreography takes place. Each inflates its body, its abdomen, its tail, to make them momentarily more imposing in the eyes of their adversary. Then… the waltz of colors operates. Each part of the chameleon’s body changes color, going from green to red, to yellow, to blue. The multicolored threat aims to curb the ardor of the adversary.
But by the way, how is the chameleon able to change color? To understand it, we must take a journey into the infinitely small, to the heart of the chameleon’s skin. Because the cells of his skin are equipped with a secret weapon: they contain nanocrystals, that is to say crystals, like those of salt for example, so small that they are invisible to the naked eye! Depending on the biological state of the animal, these crystals approach or move away from each other. And they then reflect the light differently! Thus, when a chameleon is relaxed, the microscopic crystals present in its skin are tightened, they reflect the blue color which comes to mix with the yellow pigments naturally present in the skin of the chameleon. As a result, our little lizard has a pretty green color. But, when the chameleon is agitated, things get complicated…
The colors of the chameleon’s body reveal its health and intentions
The helmeted chameleons participating in the experiment were placed in a large transparent box, face to face, each on a branch. Then, the window that separates them is lifted, to allow the chameleons to face each other. During this experiment, the researchers studied no less than 28 body regions of chameleons. Thanks to a camera, they do not lose a single crumb of the behavior of the fighters during the tournament. And what they discovered exceeded their expectations. As the researchers imagined, when the two chameleons meet, they adopt an intimidation strategy that involves changes to their bodies. They swell, as seen, and the chameleon’s skin changes from a fiery green to hues of red, yellow, or blue. But what surprised them was that they discovered that these color changes actually had a purpose!
Depending on the intensity and speed of color change on different regions of the chameleon’s body, researchers have found that they can predict the outcome of fights! For example, the more the colors of the stripes present on the flanks of the chameleon are bright and change quickly, the greater the probability that it will approach its adversary to fight it. But there is even more impressive. The colors of the chameleon’s head predict who will be the winner of the fight. Yes yes ! Thus, while the chameleon’s stripes allow it to express its motivation, its head provides information on its ability to fight. All this thanks to the measurement of the speed of change of colors and their intensity. This is a very useful power for the chameleon! Because when it’s time to fight, the chameleons turn slightly to the side, letting their stripes appear in the eyes of their opponents, a way of saying, “I’m ready to fight” or on the contrary, “I’m a supporter of the peace “. When the fight is confirmed, the two chameleons approach each other to be able to indulge in what is called a head fight. It is then that the color of the head informs everyone regarding the abilities of the adversary that he must fight. Convenient isn’t it?
So, contrary to popular belief, chameleons don’t change color to blend seamlessly into any colored background, but rather to communicate their emotions, such as motivation to fight, or to convey their abilities. But that’s not all ! Chameleons are ectothermic, meaning they draw heat from their surroundings to keep their bodies at the right temperature all year round. These survival aces are therefore also able to change color to adapt to weather variations and always stay around 20°C. Practical ! Researchers don’t yet know how chameleons are able to express their fighting abilities by changing the color of their heads. This might be because healthier individuals produce more vibrant colors, through more efficient biological reactions. But we still have a lot of work to unravel the mysteries of the incredible powers of the chameleon.
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