Hermit Crab Moulting - What To Know

Australian land hermit crabs belong to the category of Arthropods, requiring periodic molting of their exoskeleton to facilitate growth.

During moulting, a hermit crab sheds its tough exoskeleton, which should not be mistaken for its shell. The exoskeleton refers to the rigid skin covering the hermit crab's body. Unlike mammals, hermit crabs do not have bones; instead, their bodies consist of soft tissues shielded by the hard exoskeleton.

During the moulting process, hermit crabs experience a high level of sensitivity and stress. At this time, they will burrow deep into the substrate to create a secluded, dark air cave where they will undergo the shedding of their exoskeleton over the course of several weeks or even months. The new exoskeleton that emerges will be fresh and soft, rendering them vulnerable to potential attacks. Therefore, it is crucial to avoid overcrowding the tank. The hermit crab will remain in its cave until the new exoskeleton has hardened sufficiently, ensuring a safe return to the surface.

Providing a deep, moist substrate is crucial for ensuring the safe completion of the moulting process for hermit crabs.

The duration of the moulting process in hermit crabs is directly proportional to their size. Smaller crabs undergo shorter moulting cycles but moult more frequently, while larger crabs have longer moulting cycles and moult less frequently compared to smaller ones. The moulting period can vary from a few weeks to over 6 months, with no fixed timeframe as it varies for each individual crab.

Pre-Moult Signs

Excessive Eating & Drinking - Before undergoing molting, a hermit crab significantly increases its consumption of food and water in order to develop its molt sac, a small sac situated on its abdomen where it stores essential nutrients and liquids for the molting process. These molt sacs enable the hermit crabs to sustain themselves for extended periods while buried under the sand.
Excessive Digging - Hermit crabs will engage in extensive digging and create molt tunnels as they prepare for the imminent molting process. This behavior is a natural and expected part of their lifecycle.
Changing of Shells - While not a definitive indicator, sometimes hermit crabs may switch to a different shell, either larger or smaller, before undergoing the molting process.
Sluggish Behavior - Hermit crabs are typically inactive during the moulting process. Prior to moulting, they may exhibit reduced activity and move more slowly.
Eye Changes - Typically, their eyes exhibit a glossy black hue; however, prior to moulting, a cloudy appearance may be observed.

Freshly Moulted Signs

Hairy Legs - Upon molting, a crab will exhibit very hairy legs.
Sharp Black Nail Tips - Upon a successful moult, the small black nail tips will become extremely sharp and obvious to the eye.
Colour Change - Following a molt, a crab's coloration may appear either lighter or darker compared to its pre-molt stage.

Stages of Moulting -

Stage 1 (pre-moult) During this stage, the hermit crab begins to accumulate fat in their moult sac as part of the moulting process preparation.
Stage 2 (moulting) At this stage, the previous exoskeleton will begin to molt from the body.
Stage 3 (post-moult) The mature exoskeleton has been shed, and the emerging soft exoskeleton is in the process of hardening. At this stage, the Hermit Crab will consume its discarded exoskeleton to facilitate the restoration of its vigor. It is crucial that the Hermit Crab consumes its old exoskeleton prior to resurfacing. The exoskeleton is rich in calcium, vitamins, and minerals.

FAQ -

How to tell the difference between a shed exoskeleton and a crab? Should you come across a crab-like creature lacking a shell, it could likely be an exoskeleton that has been shed. An empty exoskeleton will easily crumble when gently squeezed. Conversely, if the object feels substantial and fleshy, it is indeed a crab.

Do hermit crabs leave their shell during moulting? The hermit crab remains inside its shell while undergoing the moulting process.

What happens if a moulting crab is disturbed by myself or another crab? It is crucial to exercise caution during your crab's moulting period. Avoid any actions that may disturb the crab, such as digging, touching, or moving it. If a crab in the process of moulting is encountered by another crab, there is a risk of the moulting crab being consumed by the intruder.

How many types of moults are there? 2 - Beneath the substrate moulting and surface moulting. Surface moulting is considered an immediate emergency and should be promptly addressed with proper care. For more information on surface moulting, you can refer to our blog post here https://www.happyhermie.com.au/post/surface-moulting-a-hermit-crab-emergency

Will my hermit crab change shells after every moult? Your crab will change shells at its own discretion, whenever it is prepared to do so, regardless of the stage.

What do I do if my crab comes up from their moult too early and they are still soft? If your Hermit Crab emerges prematurely following a molt, it may exhibit a notably pale and delicate appearance, rendering it highly susceptible to potential attacks. It is advisable to separate such individuals from the group until their exoskeleton has fully solidified and they have regained their vitality.

What diet should I offer my hermit crab after moulting to support their exoskeleton health? An abundant amount of calcium, the selection includes Cuttlefish Bone, Sand Dollar, Star Fish, Sea Urchins, Oyster Shell, among others. These superfoods are rich in antioxidants, vitamins, and minerals, including Bee Pollen, Blackstrap Molasses, assorted Fruits and Vegetables, as well as high-carbohydrate and beta-carotene-rich foods.