What To Do If Your Hermit Crab Is Out Of His Shell

Hermit crab and shell
Hermit crab and shell. Getty Images/Jeffrey Hamilton

Sometimes owners will find a hermit crab suddenly out of its shell. When this happens it is important to not panic. If your hermit crab isn't in its shell, it is an indication that something is wrong, as this is not a normal hermit crab behavior.

Why Did Your Hermit Crab Leave His Shell?

  • Another crab may have taken your hermit crab's shell - Crabs will fight over desirable shells but will also sometimes steal a shell while the shell-less crab was trying out another empty shell.
  • Stress may have caused your hermit crab to leave his shell - A common reason to have a stressed hermit crab is that something is wrong in their environment. This can be from the humidity being too low or too high (it should be 70-80 percent) or having incorrect temperatures (often it is too warm). Other stressors such as being kept from the food dish can lead to crabs coming out of their shells as well.
  • The shell could be irritating your hermit crab - Sometimes sand or another foreign object gets in the shell or sometimes fungal infections or mites in the shell can cause a crab to evacuate.
  • You aren't offering a good enough shell selection - A good variety of shell sizes and styles should always be provided so crabs have plenty to choose from.
  • Your crab might be molting - Sometimes a crab will come out of its shell to molt, though this is also unusual unless the crab is stressed.

In any case, when a hermit crab is out of their shell, the crab is very stressed and also very vulnerable.

You must both protect the crab by keeping other crabs away from them and entice him back into a shell.

How Do You Make Your Hermit Crab Go Back Into His Shell?

  1. First, protect your hermit crab that came out of his shell from other hermit crabs by moving him to an isolation tank or "fencing" it off with a cut off soda bottle.
  1. Next, make sure the crab has a variety of appropriately sized shells to choose from. Some crabs are quite particular about the shape of the opening and style of the shell. Always try to have larger shells of the same style your crab used to wear available (be sure to boil all shells for 5 minutes then tap out the water on a hard surface to make sure there is nothing lodged in the shells. Then dip them in de-chlorinated water and drain most of the water out again).
  2. Ensure your hermit crab enclosure has ideal humidity levels. The humidity is critical to hermit crab health and should range from 70-80 percent (get a hygrometer and make sure your levels are appropriate). The correct humidity is essential in allowing the hermit crabs to breathe (they have modified gills for breathing and the correct humidity is needed for the gills to function properly).
  3. Mist the crab regularly (a few times a day at least). Their gills (on the sides of the body) need the moisture.
  4. Make sure the tank is not too warm (not above 80 degrees Fahrenheit), but also not below 72 degrees Fahrenheit (22 degrees Celsius). Ideally, the substrate in your tank will have a temperature gradient from 72 degrees on the cooler side of the tank to 80 degrees on the warm (heated) side.
  1. Other than misting and providing food and water, leave the crab alone and in the dark. The peace and quiet may help him feel secure enough to try on some more shells.

Edited by Adrienne Kruzer, RVT