Cast off the old, show off the new.

John Grundy News, Revealing Reptiles


Skin Shedding, Sloughing & Ecdysis are all terms relating to the growth habit of losing the outer skin layer in reptiles.

The way in which reptiles grow is as fascinating as all the other secretive aspects of their lives. In order to gain in size they need to cast off the old layer of skin. This process is called shedding, sloughing or in ‘clever speak’ ecdysis, the definition of which is seen below.

(Zoology) the periodic shedding of the outer epidermal layer in reptiles. 

A shed skin is often referred to as a slough. In snakes the skin is sometimes sloughed off in one single piece. Lizards have the added complication of legs, apart from the legless ones, and so skins are more usually sloughed in tatty bits. Some lizards eat the old skins as it is shed. Geckoes can often be seen pulling at loose skin with their mouths and devouring the chunks once they are released. You may think this sounds disgusting but we eat bits from our own bodies often enough.

Sloughed adder skin

An intact snake skin can tell you a lot about the snake itself. You can see the pattern in the slough and if the tail is intact you can count the subcaudal scales to help determine the sex of the snakes (there’s another blog topic altogether). In adders if the sloughed head is intact you can identify individual animals from the distinct markings on the top of the head.

A common question I get asked is ‘how often do they shed?’ I generally compare reptile growth patterns to that of trees. They all grow very rapidly in their first couple of years if the food supply is abundant. As the reptile or tree ages the growth rate slows down. They never stop growing or begin to shrink as humans do. They continue to grow at a much slower rate until they die. A juvenile reptile might slough 3 to 4 times in a year whereas an adult usually only sloughs once ( I am talking about wild reptiles here, not captive reptiles which receive artificially high amounts of food and live in constantly controlled temperatures). Late March to April are good times to look out for recently sloughed adder skins. They are woven into bracken and heather which they use to help peel the skin off. The skins are inside out when we find them. Snakes always slough from the head first. They can not reverse out. Always exercise care when extracting a skin from the wild. Make sure it isn’t still attached to its owner first or that the owner isn’t sitting near by. Wear gloves when handling sloughed skins as they can contain numerous salmonella bacteria.  A great way to preserve snakes skins is to laminate them between layers of laminating plastic.

Adder with clouded eye during sloughing.

When reptiles are about to slough they stop feeding for a few days beforehand. A lubricating fluid is released between the old and new skin layers. This causes the reptiles to look milky or grey in appearance. Their eyes cloud over and they become very nervous due to not being able to see very clearly at all. Shortly before shedding the fluid clears up and their eyesight is restored to its normal state. By rubbing their noses against rough timber, stone or vegetation they split the skin across their faces and begin crawling through rough vegetation to peel it off. It can be a slow process and can leave the snakes vulnerable to predators. As with many other chapters in their life cycle, sloughing is often done in dense cover and seldom witnessed by people.

Vividly coloured fresh from the slough.

Newly sloughed reptiles are at their most glorious, with their colours being particularly vivid. The first slough of the year usually precedes the mating season, so all the males are looking at their best when they encounter the females. The females choose who to mate with, depending on size and overall health, which is judged on how good they look not from filling out a medical questionnaire.

John Grundy

John has spent more than thirty years honing his skills as a spotter of our region’s elusive and well-camouflaged reptiles. He can often be found wandering the moors of Durham looking for signs of life in the undergrowth. As the Revealing Reptiles Project Officer John frequently delivers reptile survey training to groups and individuals.

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