All About Hermit Crab Growth and Molting: How They Do it?

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Hermit crabs are especially popular with kids because they’re tiny, cute, and because it’s fun to decorate their home. They are also inexpensive to purchase, but if you’re going to buy one it’s best if you learn something about them first.

Learning about hermit crab growth and molting is an important part of the process, but do not worry because taking care of these creatures is not exactly complicated.

Only a small number of hermit crabs are land-dwellers, but those are the ones described here because they are the ones people often keep as pets.

What Are Hermit Crabs?

Worldwide, there are 800+ species of hermit crabs, but only one freshwater hermit crab and only around a dozen semi-terrestrial species. The latter are also called land hermit crabs and are the type that people keep as pets. Hermit crabs are omnivores and typically eat things such as pieces of dead animals, very tiny mussels and clams, and microalgae.

Hermit crabs are crustaceans but they are not actual crabs. Instead, hermit crabs are more closely related to certain types of lobsters.

Hermit crabs have an exoskeleton that is not completely hard like regular crabs, and every 6 to 18 months they shed their old exoskeleton to make room for a larger one to form. This is necessary for the health of the crab and so they can grow properly.

They are called hermit crabs because they remain alone in their shells, although they often gather in groups with hundreds of other hermit crabs in the wild, making their name a bit of a misnomer. The molting process usually takes 4 to 8 weeks, but sometimes hermit crabs will simply find another shell that has been discarded and make themselves at home there.

The Growth and Molting Process of Land Hermit Crabs

Kids who keep land hermit crabs love to watch them molt and start to walk around without any shells. There are actually three stages of the molting process: pre-molt, mid-molt, and post-molt, and each is unique in its own way. There are also two types of molting, and you’ll automatically know that your land hermit crab is molting because their exoskeletons can be seen in their cage!

Molting can occur two ways: underground molting and surface molting. The latter is fairly traumatic for land hermit crabs even though they tend to recover fairly quickly.

In addition, land hermit crabs tend to molt while they’re isolated from other hermit crabs, mostly because the process is such a distraction to any other hermit crabs in the area.

When you see hermit crab growth shells in the cage, they can be noticeable and colorful or barely noticeable at all because they are sometimes almost clear in hue.

Still, if you pay attention it shouldn’t be difficult to determine that molting has taken place. If you look hard enough and take note of the crabs’ behavior, it’s easier to determine when molting is taking place.

What Do Crabs Do When They’re Molting?

You can – and should – look for certain behaviors and changes in your land hermit crab that will signal that they’re molting. Keep in mind that land hermit crabs are stressed when they’re molting, and that stress may result in their death.

If hermit crabs are molting, the following signs might be evident:

  • Behavior that is a bit different. Your crabs may vomit, become very restless, or even eat less than they normally do. They may also steer clear of their discarded shell and may even hide from the world for a while.
  • They may generate new limbs. During the molting process, the abdomen will often shrink up dramatically, with the next step being the growth of brand-new legs. They can also change in color and overall look.
  • They start to look different. Many land hermit crabs that are molting have shells that become more rounded in shape and their color becomes a lot lighter and duller. Many times, all of your molting hermit crabs will look exactly alike to the viewer!
  • They may exhibit excessive digging. Crabs dig naturally even when they aren’t molting, but if you notice that they are digging constantly, it could be because they are molting, especially if they also look different and show changes in their appetite.

It’s important to leave your hermit crabs alone during the molting process. Handling them might give them extra stress that they don’t need.

Making sure that the hermit crabs’ cage is clean and there is plenty of fresh water available to them at all times is also important. It’s also best to set up an isolation cage and place your molting crabs there so they can be separated from the other hermit crabs.

Is it a Good Idea to Have a Land Hermit Crab as a Pet?

Many people wonder if they should keep land hermit crabs as pets. It is certainly possible and indeed fairly common, but if you’re going to do this it’s a good idea to learn exactly how to provide them with the care they need to survive and thrive.

It isn’t enough just to put some sand and a few rocks in a container then release your crabs; they need more than that.

First, pour sand or non-acidic soil about three inches deep into the cage, and make sure that the cage is big enough for all of your crabs. They need fresh water every day and salt water once a week. The cages should be placed in a humid environment and they can eat almost everything except avocados, including fruit, raw fish, and cooked beans, chicken, and corn.

You can spray their soil with water every day to keep it moist, and you can put bigger shells in there so they’ll have something to crawl into when they outgrow their smaller shells.

Keep in mind that land hermit crabs will not reproduce because they need the ocean to do this, which means that you don’t have to worry about the cage being overrun with crabs.

Is Molting an Area for Concern?

Some people dislike when their land hermit crabs molt because it looks funny, the crabs’ behavior can change, and they think it’s abnormal or that there’s something wrong with the crabs.

Just know that molting is a very natural process for hermit crabs because like other living creatures, they continuously grow bigger physically.

In fact, land hermit crabs can live for 15 to 20 years and can grow from half an inch in size up to around 16 inches in size. It’s important to make sure that you have shells they can use after molting because occasionally, hermit crabs will eat their shells for their vitamins, minerals, and calcium. Besides, many pet stores sell crab shells that are quite unique and attractive.


Land hermit crabs usually molt once or twice a year, and this is normal. They can exhibit certain behavior when molting, such as hyperactivity or restlessness, lack of appetite, vomiting, excessive digging, a lighter color, and even growing new limbs (most commonly new legs).

If any of these things are concerning you, you can always check with your vet to see if something needs to be done about it.

Once the hermit crab molts, make sure that they have a shell ready to crawl into that is slightly bigger than the previous one. This will keep them around for a long time.


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