Few, if any, animals spend their entire lives in the same skin. An animal’s outermost layer is exposed to the full force of the elements. It gets battered, burned, scuffed and scarred and accumulates parasitic ticks, fleas and fungi.
Some skins are more durable than others. But durability comes at the cost of flexibility: the rigid, jointed exoskeletons of insects and the rest of the arthropods restrict the growth of the tissues within. Either way, old skins need shedding to make way for the new.
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Most animals, from nematode worms to mammals, shed their skin in one way or another. Some do it continuously, flake by flake. Birds, mammals (human skin makes up the bulk of house dust) and most reptiles are flaky types. Snakes are not most reptiles, though. Their lack of limbs means they do many things differently, one being that they are able to slip off their old skin in one go and in a single piece.
How do you know when a snake will shed its skin?
You can tell when a snake is about to moult because its eyes go misty. Snakes don’t have eyelids, so protection of the delicate eyeballs is provided instead by discs of transparent skin, called brilles. The outer layer of these must be shed, too, and the mistiness is the result of a build-up of fluid between the top layer and the replacement one beneath, which causes the two to separate from each other. Puffy and virtually blind, moulting snakes are not at their best.
How do snakes shed their skin?
Quite understandably, snakes stop feeding and tuck themselves away somewhere safe for a few days. At some point, the fluid between the old and new skin is reabsorbed, causing the old skin to dry out and split along a line of weakness around the mouth. It can then be rolled back off the body like a sock being turned inside out. In the absence of limbs to help this process along, snakes rub themselves up against hard, abrasive objects. The shed skin is a ghostly facsimile that reproduces the finest surface details of the snake itself – even the lining of the nostrils.
Do all snakes shed their skin?
Not all snakes shed all of their skin, though. Rattlesnakes, for example, hang on to one little piece, which serves a very specific function. A rattlesnake starts life without a rattle. During the first moult, the hindmost section of the shed skin breaks off and remains attached to the tip of the tail to form the first bulbous segment of the rattle. Another segment is added at each subsequent moult. Because the sound is produced by these segments clapping together when the snake shakes its tail, a rattlesnake is not capable of rattling until it has shed its skin twice.
Main image: a bush viper snake shedding its skin/Credit: Getty
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