Hermit crabs do not grow their exoskeleton to protect themselves from predators; so they have to use different shells to protect vulnerable bodies from predators or any other work like storing water to dampen their gills so they can breathe properly. In the evolution of time, it became important, like a part of the body. A hermit crab cannot live without its shell.
Hermit crabs usually use sea snail shells that were once used by them. Almost all of the hermit crabs use gastropod shells that are found lying on the beach or in the ocean. They start the journey of finding new shells when they are around 20 days old; once the perfect shell is found, they don’t leave the shell unless they find a better one, and every time after molting and getting bigger.
If hermit crabs lack shells, which is common these days, they wear anything they find, including plastic container bottle caps, land snail shells, etc. But the problem is that anything without sea shells is not suitable for hermit crabs. Like land snail shells, they are thin and can be invaded by predators at any time and they do not feel safe wearing these shells.
Sometimes hermit crabs gather at the seashore and exchange shells among themselves. Nevertheless, they attack other hermit crabs to take over the shell when they cannot find one, severely injuring themselves in the process.
Now you know the basics of hermit crab shells. So let’s figure out what type of shells you should give to your hermit crabs, the proper way of giving shells, and what should be kept in consideration.
Species-wise hermit crab shell selection
According to opening shape, there are mainly two different types of shells, round opening and D-shaped openings. You must know which type of hermit crabs you own. After researching their natural habitat, if you manage to find any shell from there, they would be perfect.
Ecuadorian hermit crab (Coenobita compressus)
Ecuadorian hermit crabs prefer a D-shaped opening which includes zebra periwinkle, black nerite, Babylonia shell, and sharks eye shell. There is a lot of variety in all kinds of shells. Sometimes Ecuadorians can choose a round shell. So you better give some options (3–4 for 1 crab) with different species and sizes.
Purple Pincher (Coenobita clypeatus)
These hermit crabs prefer turbos or round-shaped opening which includes tapestry turbo, spotted tapestry, carved tapestry, striped turbo, Mexican turbo, Indian top, and so on.
Indo hermit crab (Coenobita brevimanus) – also prefers round openings. These are the common hermit crabs. Other hermit crabs like strawberry hermit crab, also prefer round openings.
The information in this section is collected from the hermitcrabassociation. Check out if you want to know more.
What shells you should avoid?
Painted shells
Professionals suggest not using the painted shell, as it contains deadly chemicals that can be dangerous for hermit crabs. But if you or your children want them to look pretty with painted shells, be sure to give them a variety of options with unpainted shells so that they can shift to a safer one when they feel uncomfortable.
Damaged shells
Hermit crabs do not feel safe in broken shells unless they have no other choice. They have to store water in it, which the broken shell won’t do. If the crack or hole is on top, that’s less harmful. If anyhow, it broke after the crab getting into it. Don’t force it; let it change on its own.
Glass shell
A transparent or translucent shell may seem helpful and awesome. Because you can see if any parasite or small stone is causing any problems and overall hermit crab’s abdomen health. However, glass can magnify light, which can make the vulnerable abdomen hot even with a normal LED light and it can also cause sunburn.
Preparing shells for hermit crabs
- Boil the shells for 8 to 10 minutes, ensuring there are no bacteria or any living organisms.
- Don’t touch it barehanded because it becomes extremely hot and let it be fully cold.
- Any stone inside the shell can make hermit crab uncomfortable and force it to leave the shell. So remember that.
- Place the shells upside down in the enclosure, with 3-5 shells for 1 hermit crab.
What happens if a hermit crab can’t find a shell?
The choice of shells for hermit crabs can be influenced by various factors, including geography, availability of shells, shell size and shape, species of hermit crab, environmental factors, competition and predation, and human activities such as coastal development and pollution, which can also affect the availability of suitable shells for hermit crabs.
If a hermit crab can’t find a perfect shell, its exoskeleton will become dry and vulnerable. Land hermit crabs need to dampen their gills and they can’t do it without their shell. A hermit crab will become more vulnerable to predators and won’t survive for long. It is also applicable to a captive hermit crab.
Sometimes, you might see giant hermit crabs and giant robber crabs (coconut crabs) without shells. It doesn’t mean they don’t need shells; they just can’t find a perfect shell.
Why do hermit crabs change shells?
Gastropods’ shells grow bigger with time but a hermit crab shell can’t grow as it does not have any biological connection with the body. So hermit crabs have to manually change their shell when the old one doesn’t fit. They come out of the shell and find a new shell. The cycle goes on until their body stops growing.
Sometimes they may come out of their shell for reasons other than stress or health issues.
How do I know if my hermit crab needs a new shell?
The main sign is that when they are getting ready to molt (they will look ashy, confused-looking antennae, and lethargic), they will need a new shell. If the appearance looks bigger in the old shell, hermit crabs may need a new shell. Full moon is the best time to offer new shells.
