why is my hermit crab changing shells so much?

Why Does My Hermit Crab Keep Switching Shells?

Last Updated on: 14th October 2023, 01:09 pm

If a hermit crab keeps changing shells, it’s displeased with the ease of fit, comfort level, and protection afforded. The hermit crab will keep switching shells until it finds one that meets its needs.

Hermit crabs change their shells after molting because shedding their exoskeleton is associated with growth and development. It’ll feel uncomfortable if the shell is the wrong shape and size.

If a shell has been damaged, the hermit crab will seek to replace it. As a hermit crab can remember negative events, it’ll know its previous shell left it vulnerable to falls, scrapes, and predation.

Sometimes, hermit crabs don’t know what’s wrong, so they’ll switch shells in the misguided belief that this will resolve their discomfort. For example, the ambient temperature or humidity level is too high.

Ensure the living environment remains optimal, and a selection of shells is always available.

How Often Do Hermit Crabs Change Shells?

Juvenile hermit crabs change shells every 3 to 6 months as they increase in size and mass. As a hermit crab gets bigger, it needs a shell that’s the right dimensions.

Once a hermit crab reaches adulthood, growth will slow down considerably.

The average adult hermit crab molts every 12 to 18 months, vacating its shell to make the switch. Once the molt is complete, the hermit crab needs a new shell to accommodate it.

Captive hermit crabs should always be provided with a selection of new shells. These can be kept to one side of the tank, accessible to all crustaceans.

Spare shells can be collected from the beach (and sterilized) or purchased from specialist providers.

Why Is My Hermit Crab Changing Shells So Much?

When introducing a range of new shells to a hermit crab enclosure, expect the occupants to spend several days testing out different shells for size.

Animal Behavior describes this as a “vacancy chain.” Once the initial novelty of the new shells has worn off, hermit crabs should remain in one shell for a prolonged period.

If hermit crabs keep switching shells, this will be for one of these reasons:


Hermit crabs must change shells as they grow. If a shell is too small for a hermit crab’s body, it may become trapped in its shelter. Shells can be too big and too small.

A hermit crab dragging a large, oversized shell behind itself will find its movements cumbersome and restricted. This will prevent the hermit crab from climbing and indulging in other behaviors.

A shell is as vital to a hermit crab as a house is to a human. 


A hermit crab won’t be able to tolerate an uncomfortable shell, and nor should it.

Check the interior of the shell that your hermit crab is wearing. If you see spines, spikes, or shards, these will lead to discomfort for the hermit crab.

According to the Journal of Experimental Marine Biology and Ecology, up to 149 species of parasites can impact hermit crabs.

Mites can infest a hermit crab habitat, causing severe irritation.


Hermit crabs rely on their shells to protect them from predators and the sun’s UV rays.

The shell needs to be in impeccable condition to fulfill this duty. If the shell is cracked or otherwise damaged, the hermit crab will look to trade up.

Shells can be broken in various ways. Sometimes, it’s wear and tear caused over time, but more often, it’s a consequence of impact.

The hermit crab may have fallen while hanging from the tank roof or because you dropped it.

According to Marine Biology, hermit crabs will never choose a damaged shell.

why hermit crabs change shells

Competition from Other Hermit Crabs

As shells are crucial to hermit crabs, conflict for the best vessels can arise. As explained by Behavior, this process can be an amicable exchange or an act of aggression.

Usually, a dispute over shells will begin with one hermit crab tapping on the shell of another. This is a challenge for the right to use the shell. The incumbent may accept this challenge or hide.

The two hermit crabs will wrestle if the shell owner decides to fight. The victor earns the right to the shell, while the loser must find an alternative.

Behavioral Ecology and Sociobiology noted that aggression supersedes physical size in a shell fight.

Stress and Anxiety

If a hermit crab can’t determine the reason for its unease, it may switch shells.

If the problem lies elsewhere, switching shells won’t help, but the hermit crab will look to keep exchanging shells in the hope this will change things.

Temperature and Humidity

Hermit crabs will grow uncomfortable if they are too hot or cold or lack humidity.

Reduce the likelihood of shell swapping by maintaining the right tank conditions. This is known as the 80/80 rule – a temperature of 80°F and a humidity level of 80%.

Excessive Stimulation

Stimulation outside a hermit crab enclosure can upset the occupants. Hermit crabs may start changing shells, hoping to block external factors.

Examples of stimulation that can upset hermit crabs include:

  • Noise or scents that confuse the senses of hermit crabs.
  • Excessive illumination because hermit crabs prefer to relax in dim lighting.
  • Other pets, like dogs, cats, or birds, display predatory behaviors.

Hermit crabs flourish when kept in a quiet, safe location.

Excessive Handling

It’s impossible to handle a hermit crab without holding onto the shell.

Handling is necessary because you’ll need to relocate them for cleaning and otherwise interact with them.

Never handle hermit crabs needlessly or excessively.


Life can be dull for captive hermit crabs. In the wild, hermit crabs have an entire beach to explore, so they amuse themselves by burrowing, climbing, and scavenging for food.

Adapting to life in captivity may take a hermit crab a while.

Keep the hermit crabs entertained. This involves providing hiding places, climbing frames, and similar apparatus and offering new and exciting foods.

If hermit crabs are bored, they’ll seek another way to pass the time, including shell rotation.

All hermit crabs trade and exchange shells after molting, sometimes in between periods of growth. Something is amiss if a hermit crab constantly switches shells and appears unsettled.