![]() By undulating back and forth, the snake can actually make turns. It propels itself from the branch with the lower half of its body, forms quickly into an S, and flattens to about twice its normal width, giving its normally round body a concave C shape, which can trap air. To prepare for take-off, a flying snake will slither to the end of a branch, and dangle in a J shape. Once thought to be more parachuters than gliders, recent scientific studies have revealed intricate details about how these limbless, tube-shaped creatures turn plummeting into piloting. ![]() They’re gliders, using the speed of free fall and contortions of their bodies to catch the air and generate lift. In the Airįlying snake is a misnomer, since, barring a strong updraft, these animals can’t actually gain altitude. “By understanding the evolution of the eye, we can gain new insight into where snakes came from and how they adapted to a constantly changing environment and climate,” he concludes.The image of airborne snakes may seem like the stuff of nightmares (or a certain Hollywood movie), but in the jungles of South and Southeast Asia it is reality. Simões adds that many nocturnal snakes have also developed an increased ability to constrict their pupil, rendering the need to protect the eye (via a lid) essentially moot. “Diurnal snakes, however, have a yellow lens that filters out dangerous UV light and protects the retina, very similar to what sunglasses do.” “Nocturnal snakes have a transparent lens that allows them to see better at night,” remarks Simões. This evolutionary step is most apparent in the lens of a modern snake’s eyes, which are correlated with whether that snake is diurnal or nocturnal. In fact, because they had no protective eyelid, snakes’ eyes had to change too. The evolution of snake eyes didn’t stop with the loss of the lid. “This could be another important protection mechanism, the snake equivalent of sleeping with one eye open!” Snakes in yellow sunglasses “Our best guess is that a snake’s reptilian brain allows it to sleep with their eyes open,” he says. Simões says scientists really don’t know. ‘But how do snakes sleep if they can’t close their eyes?’ you may ask. “I think it was here where snakes lost the lid and picked up the scale, which allowed them to keep their eyes open all the time.” “As this transition happened, the snake’s eye became increasingly simple,” remarks Simões. One such adaptation was a move towards a more nocturnal lifestyle. “At some point, snakes shared the same space as hungry dinosaurs, so in order to stay alive, they had to adapt,” he adds. An unblinking eye for non-stop visionĪccording to Simões, this lack of eyelids is the result of a long evolutionary process. But, unlike an eyelid, a snake regularly sheds the brille along with the rest of its scales. Essentially a modified version of the scales found on the rest of the snake’s body, the brille acts similarly to an eyelid, protecting the eye and keeping it relatively moist. While today’s snakes may lack eyelids, what they do have is a transparent scale that is called a brille. “So, the best way to understand how and why snakes evolved the way they have is to look them in the eyes.” “Every evolutionary step is reflected in an animal’s vision,” he says. Simões has been studying the evolution of snake eyes for 10 years. “Because snakes don’t have eyelids, they cannot blink,” explains Bruno Simões, a researcher at the University of Plymouth in the United Kingdom. Spoiler alert: if you ever find yourself engaged in a staring contest with a snake, you’ll lose.
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