Wild hermit crabs usually claim shells that sea snails initially occupied. These marine animals vary significantly in size and shape, much like hermit crabs. Unlike land snail shells, which are soft and weak, the shells of sea snails are strong and robust.
The perfect shell for a hermit crab offers protection from predators and the rays of the sun. Many hermit crabs also prefer a shell that blends into their surroundings, offering a degree of camouflage. The shell must also be large enough to not stunt a hermit crab’s growth.
The most common shells used by hermit crabs are known as turbo shells. These shells are defined by their toughness and shape – typically tall with a broad, round opening. Hermit crabs with a flatter thorax, like an Ecuadorian or a cavipe, prefer a D-shaped opening.
Always ensure that your pet hermit crabs have a wide selection of shells. This will prevent conflict because a hermit crab that needs a change can find a vacant shell rather than challenging a tankmate.
How Do Hermit Crabs Find Shells?
Hermit crabs spend several hours each day foraging for food in the wild. During this process, they’re likely to encounter abandoned shells. If the hermit crab is outgrowing its existing shell or feels the need for change, it may try this shell on for size.
The ideal shell for a hermit crab is one that was previously occupied by a conspecific. It’s rare that a hermit crab will physically evict an incumbent crab from a shell, although this does happen. More often, hermit crabs peacefully negotiate a shell exchange.
Additionally, as per Ecology and Evolution, hermit crabs smell a distinct pheromone released when a conspecific dies. The demise of one hermit crab means that opportunity arises for others – the deceased hermit crab is leaving behind a shell to be inherited.
Captive hermit crabs also welcome the opportunity to try on different shells, especially as they molt and grow. You can gather these shells from a beach or purchase them online, leaving the shells in a tank for your hermit crabs to discover.
Whether gathering shells from the beach or shopping online, you need to understand what makes the ideal shell for a hermit crab. Finding the optimum shell is as essential to a hermit crab.
What are the Best Shells for Hermit Crabs?
There are many potential features of a good shell for hermit crabs. If you’re keen to collect some additional shells for a hermit crab tank, consider the following.
| Strength and Stability: | Hermit crabs hide within their shells when feeling afraid or threatened, so they need to feel secure within. |
| Elements of Camouflage: | Hermit crabs are naturally drawn to shells that help them blend into the background as part of their approach to self-defense. |
| Protection from the Sun: | The rays of the sun can cause damage to hermit crabs if not blocked out. |
| Space to Move: | A shell must be big enough to prevent a hermit crab from getting stuck within but not so heavy it restricts movement. |
| Room to Grow: | As per the Journal of Experimental Marine Biology and Ecology, hermit crabs that live in larger shells grow at an appropriate pace. |
| Comfortable Opening: | Hermit crabs need to be able to get in and out of a shell. Some prefer a round opening, while others gravitate to D-shapes. |
The final point is arguably the most pivotal. The shape of an opening will determine whether a hermit crab considers a shell suitable, and this varies by breed.
Of the most popular pet hermit crabs in the USA, the Caribbean hermit crab (also known as the purple pincher) prefers a round opening. These are known as turbo shells. Ecuadorian hermit crabs prefer a D-shaped opening, as this better accommodates the crab’s body shape.
When foraging for shells in person, you should be able to determine the difference between these shell styles. If purchasing shells from an online dealer, check the small print to see what you’re buying, or get in a variety of packs with all kinds of shells.
Turbo Shells
Turbo shells belong to the Turbinidae family of sea snails. These are also known as turban snails as the shape of their shell resembles a turban. Turbo shells are found on beaches all over the nation, or you’ll be able to buy them from pet stores.
Sizes and shapes vary, as do prices – some turbo shells retail for just a few bucks, while others fetch three-figure asking prices. Popular examples of turbo shell designs include:
- African
- Cinerius
- Colossal
- Dolphin
- Green
- Jade
- Magpie
- Pearl
- Petholatus
- Sarmaticus
- Silver
- Stripe
- Tapestry
An alternative to turbo shells is murex shells. These have the same opening as turbo shells but offer a little more visual splendor. Murex shells often have different shapes, including lumps, horns, and spikes.
As nice as they may look to a hermit crab collector, murex shells can be cumbersome to wear in an enclosed environment. It’s advisable to provide turbo shells wherever possible.
D-Opening Shells
Shells with a D-shaped opening are less common on American beachfronts, so you’ll need to look harder – or, more likely, purchase them from dealers. Some exotic pet stores may have these shells for sale, or there are countless sellers online that will meet your needs.
The most popular D-shaped shell is the babylonia. Belonging to the babylonia areolata sea snail, which is native to Taiwan, this shell is white with brown markings. You can find babylonia shells in many sizes.
Other D-shaped shells will come from the following species of undersea mollusk.
- Crown Conch
- Nerita Polita
- Nutmeg
- Shark Eye
- Whale Eye
Just enter these search terms into your search engine of choice, and you’ll find many pet stores, hermit crab traders, and crafters seeking beautiful shells. If you shop with the latter, ensure the shells haven’t been painted or treated in any way.
Shells That Should be Avoided
Having established what makes a suitable shell for hermit crabs, it’s equally important to understand what shells are inappropriate. Some shells will do more harm than good to your pets, whether due to a lack of strength, limited mobility, or risk of injury.
There are considerably more inappropriate hermit crab shells than there are ideal options. Hermit crabs are typically smart enough to keep away from a shell that will not serve them well but make life easier by not providing access to the following.
Land Snail Shells
Not all gastropod shells are equal, and the shell attached to land snail differs from those found in the sea. While both types of snail can reach similar sizes, peaking at around eight inches, the shell on a land snail’s back is much lighter and weaker.
Land snails don’t maintain moisture within their shells, leading to thinner walls. The shell of a land snail is unlikely to stand up to any attention from a predator. One blow and it’ll likely start to crack under pressure.
This doesn’t mean that land snail shells are useless to hermit crabs. As per the American Malacological Bulletin, these shells are constricted from almost pure calcium. This makes them a good snack for a hermit crab, which needs calcium to maintain a strong exoskeleton.
Damaged Shells
When a hermit crab puts on a new shell, it should be in exemplary condition. Hermit crabs will typically reject a damaged shell, but to be on the safe side, don’t leave them in a habitat anyway.
The obvious risk of damaged shells is the lack of protection they offer a hermit crab. UV rays from the sun could creep through all holes and cracks, while the occupant will also feel exposed when faced with an aggressive conspecific.
Another hazard of damaged shells is that they could splinter and break while worn. Shards of the shell may break off and stab a hermit crab in the unprotected abdomen, causing significant damage.
Painted Shells
If there’s one rule surrounding hermit crab ownership, it’s never to provide your pets with painted shells. Many seafront shops paint the shells they attach to hermit crabs as a marketing ploy, making the animals look more appealing to children.
Unfortunately, paints release toxic fumes, especially when housed in the warm environment of a hermit crab habitat.
Even if the hermit crab doesn’t suffocate or suffer at the hands of fumes, the paint will rapidly start to flake and fall off the shell. Curious hermit crabs will invariably eat these paint flakes, which again contain a range of toxins that can lead to sudden death.
Plastic Shells
Biology Letters explains that exposure to plastic confuses hermit crabs, leaving them incapable of making appropriate decisions surrounding shell selection.
If a hermit crab grows confused or desperate, it’ll use plastic as a shell. This is becoming increasingly commonplace, with hermit crabs relying on trash for protection.
Unfortunately, countless hermit crabs are trapped in plastic bottles and containers every year. The hermit crabs can get into the plastic but can’t get out again. These dead hermit crabs release pheromones to attract conspecifics, and the same piece of plastic claims more lives.
Glass Shells
Hermit crabs are growing increasingly popular as pets, encouraging more people to investigate different shells. This has led to a movement toward glass-blown hermit crab shells, initially created by Vermont-based artist and designer Robert DuGrenier.
There’s no denying that glass shells look stunning on a hermit crab, but we don’t recommend them. Wild hermit crabs would not approach glass to wear as a shell, and the risks posed by potential breakage and excess heat do not justify the chic aesthetic.
Cone Shells
Some turbo shells are long and conical, as opposed to the more traditional tall and stubby design that we’re used to on a hermit crab. While some hermit crabs will choose to sport a conical shell, it’ll rarely be the first choice.
Cone shells pose a logistical challenge to hermit crabs. They’re long, heavy, and cumbersome, making them difficult to carry on the back when negotiating long distances. Depending on the size of the hermit crab, they can also be tough to hide fully within.
Ridged Shells
Check the inside of a shell before offering it to hermit crabs, ensuring that it’s smooth as a pearl. If the shell contains ridges, it won’t suit your pets. At first, hermit crabs may not notice these ridges and climb inside a shell.
As the abdomen of a hermit crab isn’t protected by an exoskeleton, these ridges will quickly become painful. Every time your hermit crab moves, it’ll be poked sharpy. It’ll feel akin to you wearing a shirt lined with thumbtacks.
In a best-case scenario, the hermit crab will immediately vacate such an unsuitable shell. The ridges may already have damaged the skin, leaving your hermit crab cut and bleeding.
Hermit crabs will always choose their own shells, so don’t attempt to force them into one of your choosing. Provide the best and safest selection of shells you can.
