Hermit crabs are active animals, so watching them live their lives is entertaining. Something may be amiss if a hermit crab remains completely still, declining to move.
All hermit crabs are nocturnal, so you won’t see them moving before sunset. Even then, a hermit crab new to captivity will be stressed, so it could be several weeks for hermit crabs to become active.
If a hermit crab used to be active but has become static, it may be preparing to molt.
All hermit crabs shed their exoskeletons and grow replacements as they increase in size and mass. It’s easy to confuse a molting hermit crab with a dead animal.
Also, a hermit crab may refuse to move because it’s stressed, bored, sick, or injured.
Why is My Hermit Crab So Inactive?
Wild hermit crabs spend hours each day traversing terrain, exploring their surroundings, and scavenging for food. While this is unnecessary for captive hermit crabs, they shouldn’t stop moving entirely.
Pet hermit crabs should still enjoy scurrying around the tank. They’re surprisingly playful animals, so if you find that a once-active hermit crab isn’t moving anymore, there will be an explanation.
According to the Brazilian Journal of Biology, hermit crabs are nocturnal animals. Once hermit crabs settle in a new home, they won’t emerge from their hiding places until after dark.
Even when hermit crabs first emerge from their daylight rest, they may doze on top of the substrate.
Alas, there are more worrying reasons why hermit crabs sit there. If you’re still wondering, “What does it mean when a hermit crab is not moving?” consider the following scenarios:
Stress
All hermit crabs struggle with life in captivity when first brought home, known as post-purchase stress (PPS). You must give hermit crabs time and space to adjust.
Once a hermit crab has adapted to life as a pet, there are still stressors, including:
- The temperature is too high or low.
- Lack of humidity, which makes breathing difficult.
- Too many hermit crabs in a too-small tank.
- The substrate lacks depth, which should be at least 6 inches deep.
- A poor diet that lacks protein, calcium, or variety.
- Too much light or dark causes problems with their circadian rhythms.
- Presence of other pets around the tank.
- Handling from owners, especially before trust has been established.
If a hermit crabs stop moving, make the environment more comfortable.
Boredom
Hermit crabs will become bored and withdrawn if you don’t provide enough things to do in the tank, like climbing apparatus and hiding places.
Food should encourage hermit crabs to be active, but only if it’s sufficiently tempting. As natural scavengers, hermit crabs rarely eat the same thing twice.
Sweet tastes entice hermit crabs, but only if they smell the food.
If hermit crabs aren’t responding to food, add more saline water and humidity to the tank. According to BMC Neuroscience, saltwater is required to stimulate a hermit crab’s sense of smell.
Physical Injury
Hermit crabs have 10 legs, including the chelipeds (claws) at the front of the body. The legs can be broken due to an impact injury or shed accidentally or intentionally.
The likeliest reason a hermit crab breaks a leg is through falling. Hermit crabs like to climb and often scale the top of the tank and hang from the roof. Many hermit crabs sleep in this position.
Hermit crabs are skilled climbers, but falls can happen. Adding sufficient substrate to the ground of a habitat (a minimum of 6 inches) is less likely to cause injury.
What’s likelier is that hermit crabs shed limbs. This may occur when the hermit crab fears a rival will steal its shell or if you attempt to forcibly eject it from a shelter.
Hermit crabs are prepared to sacrifice a leg as lost limbs regrow during the next scheduled molt. Losing legs will restrict movement, as each pair serves a different purpose.
A hermit crab may become still or limit its movement until it molts and regrows lost limbs.
Molting
Molting is perhaps the likeliest explanation for a hermit crab to stop moving.
While undergoing a molt, hermit crabs stop moving for weeks or even months. Most hermit crabs become increasingly sedentary before the process begins.
Look for the following symptoms and behaviors in a hermit crab that isn’t moving:
- Eyes become cloudy and glassy, and the stalks point away from each other.
- Eating and drinking more than usual, loading up on calories.
- Skin color fading to gray and ashen.
- Digging more, often in the same location.
In most cases, these signs preempt molting. A hermit crab will bury itself under the substrate and slowly shed its existing exoskeleton, growing a new and healthy replacement.
Some people confuse molting with death, so don’t make this mistake.
If you ask, “Why is my hermit crab not moving after molting?” be patient because the hermit crab’s exoskeleton will fully harden up after 1-2 weeks.
When the molt is complete, a hermit crab will find a new shell and grow active again.
Avoiding Interaction
Hermit crabs live in large colonies in the wild. This, coupled with the docile nature of hermit crabs, means they usually enjoy the company of their species.
Hermit crabs may clash with all animals and wish to avoid interaction. If a hermit crab is being bullied over territory, it’ll usually remain under the substrate or find somewhere else to hide.
Hermit crab conflicts needn’t be long-term or intense. They often amuse themselves by indulging in good-natured fights and tests of strength, like antennae wrestling.
In certain cases, some hermit crabs prefer to remain in their shells and avoid interaction with tank mates. If either of these scenarios apply, it could explain why a hermit crab isn’t moving:
Fighting Over Shells
While hermit crabs are usually docile, conflict may arise over a coveted shell.
A large hermit crab struggling with its existing vessel may challenge another by rapping on the shell, like challenging the resident hermit crab to a duel for the shell.
If the incumbent hermit crab emerges from its shell after this rapping, it’ll be expected to wrestle for the right to remain in its shell.
If the hermit crab has no interest in risking its shell, it’ll stay inside and not move until the aggressor grows bored and moves on.
Avoiding Mating
Hermit crabs rarely mate in captivity, requiring an expanse of seawater to hatch eggs. A male hermit crab may detect a female in season and invite her to mate.
Similar to fighting over shells, the female will react in kind. She’ll emerge from the shell and begin breeding if interested in responding to a male’s advances.
If not, she’ll hide in the shell and remain still until her season passes or the male loses interest.
Death
If you find a hermit crab out of its shell and not moving, it’s increasingly likely that it has expired. Dying hermit crabs often vacate their shells so another hermit crab can seize the vessel.
As discussed, it can be possible to confuse death and molting, so you must be sure the hermit crab is no more before taking drastic action.
Alongside a lack of movement, common signs that a hermit crab has died include:
- Foul odor akin to rotting fish.
- Interest from other hermit crabs in the shell, especially if they’re eating the remains.
- Spots of mold on the skin of the hermit crab.
Mold can kill hermit crabs, so immediately remove the corpse from the tank.
