- Another crab took its shell. Crabs will fight over desirable shells, but also will sometimes "steal" a shell while the shell-less crab was trying out another shell.
- Stress; for example from something wrong in the environment. This can be from the humidity being too low or too high (should be 70-80 percent) or incorrect temperatures (often too warm). Other stressors can lead to crabs coming out of their shells as well.
- The shell is irritating the crab -- sometimes sand or another foreign object gets in the shell, or sometime fungal infections or mites in the shell cause a crab to evacuate.
- Not enough shell selection -- a good variety of shell sizes and styles should always be provided, so crabs have plenty to choose from.
- Molting (rarely) - sometimes a crab will come out of its shell to molt, though this is also unusual unless the crab is stressed.
Protect and Entice a Crab Back Into a Shell
- Protect the crab from other hermit crabs by moving it to an isolation tank or "fencing" it off with a cut off pop bottle.
- Make sure the crab has a variety of appropriately sized shells to choose from. Some crabs are quite particular about the shape of opening and style of shell. Always try to have larger shells of the same style your crab used to wear available.
* Boil all shells for 5 minutes, then tap out on a hard surface to make sure there is nothing lodged in the shells
* Dip in dechlorinated water with Stress Coat, and drain most of the water
* Place a number of appropriate shells in with the isolated crab
- Ensure ideal humidity levels. The humidity is critical to hermit crabs, and should range from 70-80 percent -- get a hygrometer and make sure. The correct humidity is essential to allow the hermit crabs to breathe (they have modified gills for breathing and the correct humidity is needed for the gills to function properly).
- Mist the crab regularly (a few times a day at least) -- their gills (on the sides of the body) need the moisture.
- Make sure the tank is not too warm (not above 80 F), but also not below 72 F (22 C). Ideally the substrate in your tank with have a have a temperature gradient from 72 F (22 C) on the cooler side of the tank to 80 F (26 C) on the warm (heated) side.
- Other than misting and providing food and water, leave the crab alone and in the dark. The peace and quiet may help him or her feel secure enough to try on some more shells.