As your hermit crab grows, it needs shells that fit its evergrowing body. Since our little hermies cannot grow a shell themselves, they have to find larger shells left behind by snails, slugs, or other hermit crabs.
With this raises the question, how often do hermit crabs change shells? I wondered the same thing, so I did some research.
Hermit crabs change shells as they grow, most often before or after they molt. Most hermit crabs molt every 12-18 months, so expect your hermit crab to change shells at least twice every 12 to 18 months.
It turns out that crabs need an optimal environment full of shells to go through a successful shell change. Let’s look into why crabs change shells, a little bit more detail into how often, and how we can help our little hermies along the way.
Hermit crab shell changing habits
In a perfect world, we could predict when our hermit crabs would change shells and how often to make our jobs as pet owners much easier.
It turns out that there’s no way to predict when a hermit crab will change its shell. It’s entirely up to the hermit crab when and where it changes its shell for a new one.
There are, however a few factors that can give you an idea of how often your hermit crabs will change shells. Here are two:
1) Its Species
Some species of hermit crabs like to change shells more frequently than others.
For example, the Carribean Hermit Crab (also known as a Purple Pincher Hermit Crab) is very inclined to changing its shell.
Whenever a Purple Pincher stumbles upon a shell that’s, in its opinion, better than its current, it will change shells then and there. Sometimes they can be indecisive and switch back and forth until one feels right.
Other hermit crab species choose not to switch shells as often. The Ecuadorian Hermit Crab is very hesitant when it comes to changing shells.
These finicky little creatures only change shells when they absolutely need to, usually when they’ve entirely outgrown their previous shell.
Everyone has his or her own reason to why this is the case. Some say this is because of the Carribean and Ecuadorian crab competing for the same type of shell, which is not the case.
According to hermit-crabs.com, Ecuadorian crabs need shells that are a bit different than the average Caribbean’s. Ecuadorian crabs are much flatter and wider than other hermit crabs, which makes them look for a shell with a flatter, coin slot-shaped entrance.
This is much different than the usual round or oval-shaped shell openings most Purple Pincher Hermit Crabs are used to.
Maybe this is the reason why Ecuadorians are very picky when it comes to choosing shells. In any case, be sure to supply your crab with at least 3 shells, some a little smaller and others a little larger than their current shell.
2) The availability of shells
Most times a hermit crab will change its shell because of the abundance of shells available to them. They will be especially interested in trying a few new shells on for size if they are a Carribean Hermit Crab as mentioned previously.
They will also do the opposite. A lack of empty shells in their crabitat will cause any crab to stick with its own shell. This can be detrimental to the crab’s health over a long period of time.
Because of this, you need to supply your crabitat with plenty of shells for your hermit crabs to choose from. Whenever they change shells is entirely up to them, you just need to allow your pet crab to make that choice.
I mentioned earlier that each crab in your environment needs at minimum 3 shells. Avoid painted shell as chipping paint can be toxic. At least one needs to be a little bit larger than their current shell, and another needs to be a little bit smaller. We’ll get into why later.
A good rule of thumb is to buy shells with an opening 1/8″ larger/smaller for your hermit crab. Also, keep the openings consistent. If its current shell has an oval-shaped opening, buy a new shell with an oval-shaped opening.
Why hermit crabs change shells
Does your hermit crab need a new shell?
Well, we can only answer that question by going into why hermit crabs change shells.
Hermit crabs change shells for 3 reasons: they are preparing to molt, they just finished molting, or they have found a shell that they like better compared to their current one.
Just keep in mind that this depends on the hermit crab’s species. Ecuadorian crabs will sometimes choose not to change its shell, even after its molt.
When hermit crabs are preparing to molt, sometimes they will move to a smaller shell beforehand. This is because hermit crabs shed a fine layer of their skin and actually finish the molting process noticeably smaller than before.
Once the hermit crab has had a week or two for its new skin to form and harden, it will move to a larger shell to call home. This is the most important time to have extra shells in your cage. Your hermit crabs deserve the best and should never settle for an ok shell. 3 to 5 shells to choose from are plenty per hermit crab.
The last reason is that your crab is “house-hunting”. This usually occurs a few weeks after a long molt. A hermit crab house hunting will trade shells very often. It’s not uncommon to see a hermit crab going back and forth between each mobile home, changing its shell several times a day.
Your hermit crab is just trying to find the very best shell. Do not worry about your crab, it’ll make its decision soon enough.
Does your hermit crab need to change shells?
There’s no rush in changing shells. Hermit crabs do it on their own time, given that you gave them everything they need. More on that later.
For now, let’s see if your hermit crab really needs to change its shell.
A good way to check is to hold your hermit crab by the end of its shell. This is not something you should regularly do, as it is stressful for the crab. For now, it’s one of the easiest ways to check.
Hold the crab so that its shell’s opening is facing the ceiling. This should cause your crab to sink back into its shell. If it does not sink its legs and/or claws back into the shell, it may be a bit cramped inside.
This means your little hermit crab is in need of a new shell! Let’s make sure you have everything you need to change.
Encouraging your hermit crab to change shells
Sometimes, your crab may seem like he or she just does not want to change their shell.
You can’t exactly force it to happen. A hermit crab would sooner let itself get torn in half than be forced out of its shell.
Instead, you need to prepare and make sure your crab has everything it needs to change shells.
First, as mentioned before, you need the right shells. Remember that Ecuadorian crabs need shells with a thinner, more narrow shell and Carribean crabs need a round, oval-shaped opening.
Painted shells are a no-go. The paint could chip off the shell and harm your hermit crab!
You should have at least 3 extra shells per hermit crab. I recommend having one a bit smaller, and one a bit larger than the crab’s current shell. This gives your crab plenty of flexibility when choosing its shell.
Lastly, make sure you keep the extra shells clean. Boiling the shells for 15-20 minutes every other month will keep them free of bacteria and dirt. Just make sure you check inside each shell! You don’t want to boil your crabs!
Takeaway
You cannot predict when your hermit crab will change its shell. Instead, prepare for when it does happen. Give your crabs plenty of extra, clean shells that are the right size.
When your hermit crab inevitably does change shells, write it down on your calendar. Maybe you will see a trend and be able to predict its next shell change.
Related Questions
How long can hermit crabs live without a shell?
Hermit crabs can live up to 2 weeks without a shell, given that they are well cared for. If your hermit crab ever does vacate its shell, present it with plenty of extra shell options to replace its old one.
Do hermit crabs come out of their shells to die?
When hermit crabs die, they most often hang out of their shells and give off a foul odor. If your crab is ever drooping out of its shell, it may either be cooling off or be dead.