Hermit crabs are decapod crustaceans that belong to the superfamily Paguroidea. Scientists have identified more than 1,100 types of hermit crabs, most of which are ocean-based.
While unconventional pets for many people, hermit crabs are becoming increasingly popular. Available from seafront gift shops or online, obtaining pet hermit crabs has never been easier.
It takes hermit crabs time to adjust to life in captivity. Once they recover from post-purchase stress (PPS), hermit crabs can provide years of fascination and enjoyment.
Interesting Hermit Crab Facts
Here are some fun facts you may not know about hermit crabs:
1/ Hermit Crabs Aren’t True Crabs
Both animals are decapod crustaceans with ten legs (including two claws), but hermit crabs aren’t born with a shell. In the wild, true crabs sometimes feed on hermit crabs.
Most true crabs have two identically-sized claws, known as the chelipeds, but a hermit crab has one claw much larger than the other.
Hermit crabs also have a slightly different anatomy than true crabs. True crabs have solid, armored abdomens and shuffle from side to side when walking.
Hermit crab legs bend forward and back, so they can walk in a straight line.
2/ Hermit Crabs Aren’t Hermits
The term ‘hermit crab’ stems from the fact that they rarely share shells.
A hermit crab takes its shell seriously and will protect it. To a hermit crab, a shell is its home, so it won’t want to be evicted without putting up a fight.
Hermit crabs dislike solitude, so they live in colonies of 100 or more.
3/ Life in Captivity Can be Hard
Hermit crabs can adapt to life as pets, but it doesn’t necessarily come naturally to them. All hermit crabs will undergo post-purchase syndrome (PPS) in captivity for the first weeks.
While a hermit crab undergoes PPS, it’ll likely remain hidden under the substrate and rarely emerge.
4/ Strict Social Hierarchy
Hermit crabs are docile, but they sometimes fight with each other. Part of this is due to the strict social hierarchy into which a colony of hermit crabs will organize themselves.
All hermit crab groups will assign one alpha, with others living in varying degrees of subservience. Most hermit crabs will accept their place in the pecking order.
Ethology confirms that hermit crabs can remember which of their tankmates are dominant and will behave accordingly. While some will challenge for alpha status periodically, the majority live in harmony.
5/ Heat and Humidity Requirements
It’s important to mirror a hermit crab’s natural living arrangements, which involves maintaining an appropriate temperature and humidity level.
Hermit crabs are used to tropical climates, so keep temperatures between 72–84OF.
Any hotter than this, and hermit crabs become uncomfortable and look to exit their shells to cool off. Any colder and hermit crabs grow static and unmoving.
Hermit crabs need a humidity level of 80% to keep their gills moist enough to breathe easily. Get a hygrometer to ensure your hermit crabs are safe and comfortable.
6/ Hermit Crabs Like Burrowing
Hermit crabs love to dig and burrow and often sleep under this substrate.
Playground sand purchased from a toy store is fine. It’s advisable to bake sand in the oven to purify it before applying it to a hermit crab tank, killing parasites and bacteria.
You could also use soil as a hermit crab substrate. Avoid potting soil, as this may contain traces of toxic pesticides or herbicides and turns to mud when wet. Coconut soil is the best choice if you use dirt.
7/ Marine And Land Hermit Crabs Can’t Live Together
Hermit crabs can be aquatic or live on land, but never both. Marine hermit crabs need to live in a heated aquarium, while terrestrial hermit crabs need a humid, warm tank.
Both marine and terrestrial hermit crabs breathe through gills.
If an aquatic hermit crab spends too much time out of the water, its gills will dry out, making breathing difficult. Land hermit crabs keep their gills moist for the same reason.
Terrestrial hermit crabs can’t breathe underwater but enjoy submerging themselves. A land-based hermit crab will hold its breath while under the water.
If this goes on too long, the hermit crab risks drowning.
8/ Terrestrial Hermit Crabs Still Need Water
As terrestrial hermit crabs like to submerge themselves in water, they should be provided with two tubs. One should be filled with fresh water and one with saline water.
Never use tap water, as this contains chlorine and copper. As per the Journal of the Black Sea, the latter is toxic to hermit crabs. Purchase bottled water or get a water purifier.
9/ Hermit Crabs Need to Live Inside
Keep your hermit crabs in a tank or aquarium within your home, as it’ll be too difficult to maintain appropriate living conditions for hermit crabs outside.
If hermit crabs grow too cold, they become sick. Living outside also places hermit crabs at risk of attack from wild predators, including birds, stray or feral cats, and raccoons.
10/ Hermit Crabs Learn to Enjoy Handling
Although they’re not cuddly pets, they can learn to tolerate or enjoy handling.
Never leave a hermit crab dangling in the air. If you need to pick them up, lift them by the back of the shell and place them in the palm of your hand. Keep your skin taut to avoid pinching loose skin.
To avoid being pinched by a hermit crab, make handling as pleasurable as possible. Place something such as strong, sweet-smelling jelly for your hermit crabs to snack on at the tip of your finger.
11/ Hermit Crabs are Nocturnal Animals
In the wild, hermit crabs spend their days hiding under the substrate to avoid predators and prevent the sun’s rays from burning them. These hours will be replicated in captivity.
If you keep hermit crabs as pets, don’t attempt to interact with them during the day. They’ll want to sleep until the sun goes in and the temperature drops. Your hermit crabs should emerge at dusk.
12/ Hermit Crabs Love to Climb
Climbing is a natural behavior in hermit crabs.
The Journal of Ethology explains how wild hermit crabs climb to avoid aggressive conspecifics. Captive hermit crabs scale walls for recreation.
Hermit crabs can and will slip and fall while climbing. Your pets should not hurt themselves if you provide enough substrate to cushion a fall.
It will be commonplace to find hermit crabs hanging from the ceiling of your habitat, akin to roosting bats. This is nothing to worry about, as hermit crabs find it relaxing.
13/ Male vs. Female Hermit Crab Differences
Male hermit crabs have hairy legs, while females have smooth legs. Females also have gonophores – tiny holes that act as the reproductive organs – at the top of their middle legs.
Do not worry about sexing hermit crabs. They rarely mate in captivity, as females lay their eggs in the ocean when ready to hatch. The small body of saline water in a habitat is too small to fulfill this function.
14/ Hermit Crabs Playfight for Fun
Hermit crabs pass the time by playfighting, which involves wrestling with antennae, known as feeler fights. Some hermit crabs also push each over in tests of strength. If this remains playful, a hermit crab flipped over will be helped up.
This is a natural behavior for hermit crabs. There’s no need to intervene unless the two animals attempt to pinch each other, which can lead to eye stalks or limbs being severed.
One hermit crab rapping on the shell of another is challenging for the right to wear a superior shell.
If the incumbent is willing to accept the challenge, it’ll emerge from the shell and start a feeler fight. The winner of the wrestling match claims the shell.
15/ Hermit Crabs Need Variety in Their Diet
As natural scavengers, wild hermit crabs enjoy a wide and varied diet. As per Animal Behavior, hermit crabs rarely eat the same thing twice in 24 hours.
Hermit crabs aren’t fussy eaters, so they’ll gleefully eat many different foods, with fruit, vegetables, and meat being firm favorites. Hermit crabs have a sweet tooth.
A hermit crab’s diet should involve plenty of calcium and protein, encouraging the growth and maintenance of a strong exoskeleton, so a cuttlebone will help.
As hermit crabs lack teeth, you’ll need to cut food into small pieces. Ensure there’s saline water and moisture in an enclosure, as this will activate a hermit crab’s sense of smell and stimulate hunger.
16/ Hermit Crabs Can Regrow Lost Limbs
All hermit crabs need to molt every 18 months or so. Molting is the process of shedding the exoskeleton and growing a replacement. The molting hermit crab will invariably increase in size following a molt.
Molting takes several weeks or even months. You won’t see your hermit crab throughout this time, as it will be buried beneath the substrate.
Molting also allows hermit crabs to regrow lost limbs, antennae, and even eye stalks. Hermit crabs may take several molts to completely regrow everything they have lost or shed.
17/ Captive Hermit Crabs Can Live for Decades
Hermit crabs have an unfair reputation as delicate and short-lived. In reality, hermit crabs can live 30 years or longer in captivity. The oldest pet hermit crab on record lived to the age of 44.
There’s much to like about hermit crabs as pets, so provide them with the best quality of life.