Hermit crabs spend most of their time inside their shells, benefitting from their protection.
All the same, even the most cautious hermit crabs should leave their shell occasionally. Not doing so suggests that a hermit crab may be stuck inside its shell and unable to get out.
Hermit crabs may outgrow their shells and find that they can’t escape. Also, a hermit crab housed in a painted shell can become trapped. It might get glued to its shell if the paint wasn’t dry.
Getting trapped in a shell is a life-threatening event. However, you can’t wrench a hermit crab from its shell, as most would rather die than be evicted against their will.
My Hermit Crab is Stuck in its Shell
To hermit crabs, a shell is a home. If a better shell becomes available, they’ll upgrade. So, it can be concerning if a hermit crab remains in its shell without emerging.
A hermit crab should leave its home occasionally, such as when alternative shells become available. If you haven’t seen your hermit crab in a while, it may be trapped inside.
There are two primary reasons why a hermit crab may become stuck in its shell:
Outgrowing Shells
Hermit crabs grow quickly when young, molting several times a year. Each time a hermit crab molts, it sheds its exoskeleton and develops a new, larger exoskeleton.
Think of the process as the crustacean equivalent of shedding skin in reptiles.
As a hermit crab grows, it’ll need a larger shell for protection. Also, a larger opening will be essential for the hermit crab to come and go.
This table outlines the optimal shell opening sizes:
| Shell Size | Opening Size |
| Small: | Opening from 3/8 to 1/2 an inch |
| Medium: | Opening from 1/2 an inch to 1 inch |
| Large: | Opening from 1 inch to 1 and 3/8 inches |
| Jumbo: | Opening of 3 inches or larger |
There’s no reason why small hermit crabs can’t live in larger shells.
As per Biology Letters, hermit crabs adapt to their shells, so movement and lifestyle will be modified appropriately. The larger a shell, the more space a hermit crab has to grow.
What’s more, a larger shell can be an effective trading tool. Nature Communications explains how hermit crabs often trade shells among themselves.
Often, when a hermit crab outgrows its shell, it cracks during molting. Once the hermit crab has regrown its exoskeleton, it’ll find a new, appropriately-sized shell.
However, the hermit crab may become trapped inside if the shell is too tough.
How to Tell if a Hermit Crab is Too Big for its Shell
If your hermit crab welcomes handling, measure it and its chosen shell.
Hold the hermit crab in your hand and use a tape measure/ruler to measure the hermit crab’s largest claw. Once you have this measurement, write it down.
Now, return the hermit crab to its enclosure and wait for it to leave its shell. You’ll need patience because hermit crabs leave their shells on their terms.
When the hermit crab leaves its shell, measure the opening. This must be a minimum of 1/8 of an inch larger than the claw measurement. Anything less will quickly become too small, which creates the risk of the hermit crab eventually getting stuck.
You could perform a simple eye test if you can’t make these measurements. If its largest claw can’t retract inside the shell, it’s too small.
Glued by Wet Paint
We advise against getting hermit crabs from seafront gift shops because they’re handled by people with a limited understanding of their care needs.
Shopkeepers paint shells different colors of the rainbow and leave them for hermit crabs. The hermit crab is indifferent to these aesthetic flourishes. It’s a marketing exercise aimed at humans.
Sadly, it’s also dangerous. Paint chips are toxic to hermit crabs and create fumes in humid conditions. If a hermit crab avoids these fates, wet paint can glue a hermit crab’s abdomen to its shell.
Is My Hermit Crab Really Stuck?
If you haven’t seen your hermit crab for a while, don’t automatically assume it is stuck.
Hermit crabs are shy, docile animals that are nocturnal by nature. A hermit crab may stay inside during the day and only emerge once it’s dark.
There are other reasons why hermit crabs remain in their shells:
Hiding
Hiding behavior is the first step of a process that culminates in burrowing.
If the hermit crab remains in its shell, it may be de-stressing, which is common when it first enters captivity. It is surrounded by new, unfamiliar stimulation. It needs time for itself to adapt.
Equally, the hermit crab may be living in inappropriate conditions, so check the temperature and humidity of the tank. The temperature should be 80 degrees Fahrenheit, and the humidity level should be 80%.
Ensure that the hermit crabs get 12 hours of dark and 12 hours of light.
Check that other hermit crabs aren’t bullying it. Also, keep other pets, like cats and dogs, away too. As explained by OIKOS, hermit crabs often hide in their shells for protection from predators.
Molting
Hermit crabs molt regularly, which can be an anxious time because it’ll have no protection while undergoing the process. As a result, some hermit crabs molt inside their shells.
A molting hermit crab will still burrow. Don’t be surprised if the hermit crab doesn’t emerge for some time, as the molt can take weeks or months.
A molting hermit crab must be left alone, so never dig up the hermit crab to see if it is stuck in its shell because the stress this causes can be fatal at such a vulnerable time.
Protecting The Shell
There are often disagreements over shells, which may result in the hermit crab refusing to leave a preferred home. It worries that, if it does so, the shell will be claimed in its absence.
This doesn’t guarantee the shell will not be stolen. As per Behavioral Ecology, hermit crabs indulge in “shell rapping,” which involves knocking against a shell, trying to loosen the incumbent’s grip.
Provide a wide selection of shells, as this will minimize the chances of one shell being coveted.
Eliminating
Hermit crabs feel vulnerable while passing waste, so they’ll poop in their shells, clearing it out later.
There’s no need to be concerned if you find plenty of waste on the substrate.
How To Tell If A Hermit Crab Is Stuck in Its Shell
As discussed, not all hermit crabs that stay in their shells are stuck. A hermit crab may be molting, hiding, or relaxing. While hermit crabs often trade shells, this isn’t mandatory.
One way to tell a hermit crab is trapped is by watching it. It may be stuck if a hermit crab attempts to leave the shell and pulls back. Test this theory further by placing a treat on the other side of the tank.
The hermit crab will likely venture toward the food in its shell. You should be able to tell if the hermit crab is comfortable, though. If it is moving awkwardly, the shell may be too small. Equally, if the hermit crab refuses food, it may struggle to eat while trapped inside.
Offer a range of new shells of varying shapes and sizes. The hermit crab will eventually grow curious about these alternative homes. If not, the hermit crab likely can’t escape its shell.
Helping a Hermit Crab Out of its Shell
Start by providing more bathing opportunities, as submerging in water douses a shell. This will eventually loosen the hermit crab’s grip, especially if it’s glued inside.
If this doesn’t work, you’ll need to take a hands-on approach to get a hermit crab out of its shell.
Never tug a hermit crab from its shell. It doesn’t matter how delicate you think you are because you’ll end up pulling the legs off, as a hermit crab will do anything to avoid being separated from its shell.
Instead, the hermit crab must be carefully cut out of the shell with a blunt, flat-edged knife. If the hermit crab is small, a paperclip may suffice. Gently slide this around the shell.
Take your time until the hermit crab is free. If it were stuck, it’d emerge to stretch its legs immediately.
At this point, the hermit crab will be stressed and anxious, so ensure it has another shell to get into that’s a more appropriate size and leave it alone.
You may find that your hermit crab burrows for a prolonged period to de-stress.
