Reptiles molt, a process scientifically known as ecdysis. This involves the periodic shedding of the entire outer layer of skin, which is necessary for their health and survival. Unlike mammals, whose skin cells are constantly replaced, reptiles replace their skin all at once in larger, visible pieces. This shedding is far more than simply discarding old skin; it is a hormone-driven process that renews the protective and sensory functions of the integument.
Why Reptiles Shed Their Skin
Shedding is primarily required because a reptile’s skin, particularly the hard, keratinized scales, does not grow continuously with the rest of the body. As the reptile increases in size, the rigid outer layer, or stratum corneum, becomes stretched and restrictive. Molting allows the animal to accommodate physical growth; young, rapidly developing reptiles typically shed much more frequently than adults.
Shedding also maintains the health and integrity of the skin. It helps remove external parasites attached to the outer scales and eliminates damaged skin resulting from minor injuries or abrasions. This renewal ensures the animal’s protective barrier against dehydration and mechanical stress remains effective.
The Step-by-Step Molting Mechanism
The initiation of ecdysis is governed by internal hormonal changes, often triggered by growth or environmental factors like temperature and light. Hormones stimulate cells in the deeper skin layer, the stratum basale, to form a completely new layer beneath the old one. This new skin is fully formed before the old layer is ready to be shed.
A thin layer of lymphatic fluid and specialized enzymes is then secreted between the old and new skin layers. This fluid acts as a natural lubricant, breaking down the connection and facilitating separation. During this phase, often called “pre-shed” or “opaque,” the reptile’s skin may appear dull. The eyes of snakes and some lizards become cloudy or milky because the clear scale protecting the eye, called the spectacle, is also separating.
Once separation is complete, the reptile uses physical effort to remove the old skin. This involves rubbing its body, particularly the head, against rough surfaces such as rocks, bark, or branches. The friction creates a tear, often starting around the snout, allowing the reptile to essentially crawl out of the old skin.
Distinct Molting Patterns Across Reptile Groups
The physical pattern of shedding varies significantly among the major groups of reptiles. Snakes typically shed their skin in a single, inverted piece, much like peeling off a sock from head to tail. This complete shed includes the spectacle, which is shed along with the rest of the skin.
Lizards, in contrast, usually shed their skin in patches, flakes, or large pieces rather than a single continuous layer. Many species, such as geckos, consume their shed skin, a behavior known as dermatophagy, to recover valuable nutrients and trace minerals.
The molting process in turtles and crocodilians is less dramatic and often goes unnoticed. Crocodilians shed their scales individually and continuously, similar to how mammals shed hair, rather than undergoing a periodic full-body shed. Turtles do not shed their skin in large sheets, though the keratin plates on their shells, known as scutes, may flake off individually over time.