How Long Does It Take A Hermit Crab To Molt


by Simon Griffiths


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If you have hermit crabs, you have probably noticed they have some phases during the year where they change their behavior for a while. Around some time of year or multiple times, they may retreat into the sand for some privacy and later re-emerge.

Hermit crabs have a hard exoskeleton that covers the front half of their bodies and a softer exoskeleton covering the other half which is the abdomen. Since hermits grow relatively quickly, there is a need for them to shed their exoskeleton. This is because the exoskeleton does not grow with the rest of the body. This shedding is what is known as the molting process. Hermit crabs, therefore, need to molt in order to grow.


How Long Does It Take A Hermit Crab To Molt

The length of time it takes for a hermit crab to molt and the number of times it does so in a year will depend mostly on its size. Smaller-sized crabs will molt for two weeks and they molt multiple times a year if the conditions are right. For the average-sized crab, molting will take around 1 to 2 months, and it will happen once or twice a year. For the larger-sized crabs, the molting process will take around 2 to 3 months and they do so once every 12 to 18 months.

What are some of the signs that a hermit crab is about to start molting?

Hermit crabs will go through behavioral transitions before the molting process. Here are some of the changes you will notice with your hermit

1. The crab will start digging.

This is part of the initial preparation process for the hermit crab. It will start to dig so that it retreats into the substrate for some privacy and protection. The sand retreats into will be suitable in terms of temperature and moisture so that it is comfortable throughout the entire process. The darkness is required so that the molting hormone can be secreted.

When the conditions in the sand are not suitable, the hermit crab will secrete a different hormone and delay the molting process. If the sand in the tank is not deep enough to be dug into, the crab may try surface molting which is unsafe for them.

Please note however that the hermit crab may just be digging because the overall temperatures of the tank are unsuitable, so check the humidity and temperature if you need to.

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2. Increased appetite

In preparation for the molting process, the hermit crab will definitely develop a bigger appetite than usual. This is because it needs to store enough fat, water, and nutrients to keep it going when it is buried in the sand. The water is also used to expand the exoskeleton so that it can be shed. The nutrients and water are stored in a grey-black bubble on its left underside.

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3. Reduced activity

Since this is a time when the hermit crab is delicate, it will become more lethargic and its antennae will look strange and folded. The antennae will also have reduced activity and there will be reduced interaction with their fellow hermits. The hermit crabs that delayed their molting to wait for better conditions to arise will especially experience more lethargy.

4. Regenerating limbs

A hermit that had missing limbs will begin to regenerate them. At first, it will have a gel-like nub appearance but as time goes by, the nub will grow into a well-defined shape.

5. Changes in appearance

Some of the changes you will observe are dull cloudy eyes that appear brownish as opposed to the normal black shiny appearance. The exoskeleton and the tips of the legs and claws will also look dull and ashy.

6. Changing shells

The hermit crab will start to change shells a bit more frequently with its changing needs. Some hermit crabs will opt to look for a smaller shell probably because it is easier to bury.

Related How Do You Remove A Hermit Crab From Its Shell and Is It Safe?

The Molting Process

The molting process has four primary stages:

  1. Proecdysis
  2. Ecdysis
  3. Metecdysis
  4. Ecdysis

Pro Ecdysis is the initial stage. This is the process whereby the hermit crab starts storing water and nutrients as mentioned above. Missing limbs will also start to reform during this stage.

Ecdysis is the process where shedding actively starts taking place. The water and nutrients will be used to help in the disintegration of the exoskeleton.

Metecdysis is the process where the freshly moulted hermit starts to harden up once again and regain mobility. The hermit will start consuming the old exoskeleton to help in the formation of the new one, so do not be quick to throw away the old one.

Anecdysis is the final and longest stage, whereby the hermit crab continues to harden its new exoskeleton with more nutrients and minerals and it adapts to the new one.

Related The Process and Stages of Hermit Crab Molting


How can you tell the difference between a moulting or dying crab?

To tell whether a crab is dying or just moulting, check for the behaviour and the smell.

The molting process does have an unpleasant odor, but the odor that will come about from the death of the hermit crab will definitely be worse.

Related Do Hermit Crabs Smell Bad and What Causes Odor In The Tank?  

A molting crab will also move and twitch from time to time, but if your hermit is still for a long period of time then it is probably dead.

If you pick up the shell and the hermit instantaneously falls out, it is also most definitely dead. Mould is also a sign of death.

Related How To Tell Whether Your Hermit Crab is Molting or Dead

What should I not do when my hermit crab is molting?

When a hermit crab is moulting, it is at its most sensitive and delicate. During the moulting process, do not disturb the crab or touch it. You should also let it thrive in suitable conditions because if the environment is unsuitable, it will produce a moult inhibiting hormone which can increase to toxic levels killing the crab.

Do hermit crabs like sand or rocks better?

Hermit crabs definitely prefer sand because it can be dug into and it is easier to regulate moisture and temperature levels in sand.

Conclusion – how long does it take a hermit crab to molt

The moulting process for a hermit crab is overall fascinating and interesting to learn about and observe. If you would like to monitor the changes, nighttime is probably best because they are nocturnal.

For hermit crab owners, remember not to disturb it even while observing and let nature run its course.

Simon Griffiths

Hi guys, my name is Simon, a fellow pet lover. I love everything about traditional and exotic pets so I am here to help you create a better home for your pets.

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