A hermit crabs shell serves two purposes: first protection of the soft abdomen and second it prevents dessication (drying out). A hermit crab that has left the protection and life-sustaining seashell home is telling you it’s in distress.
- Physically stressed from poor handling or conditions during capture, transport and/or poor pet store conditions
- Shell fight-another hermit crab has taken its shell-no suitable shell remains
- Changing shells and let go of the old one, which was shell-napped by another crab-no suitable shell remains
- Foreign body/irritant in the shell (sand, pest, fungus NOTE: crabs have been known to hide food in their shell)
- Temperature is too HIGH
- Humidity is off
- Pre-molting, although it rarely happens
Below we expand a bit on these causes.
Land Hermit Crabs endure a great amount of stress before reaching the pet store. The harvesting and shipping of hermit crabs is a very inhumane process and the crabs suffer because of it. They then arrive in pet stores, who in most cases, don’t know how to properly care for them. They arrived stressed out, dehydrated and hungry. Then you purchase them and take them home. Now severally physically damaged the hermit crab will often leave it shell to die.
If there is not a variety of appropriate styles and sizes of extra changing shells in the crabitat for the hermit crab to choose from, there may also be shell fights. This is normally dangerous for the hermit crabs within the crabitat due to the fact that hermit crabs would rather let themselves be pulled apart as opposed to giving up their protective home. Many times this leads to a hermit crab being seriously injured or even killed by the aggressive hermit crab in search of a comfortable shell.
There are times too when a hermit crab is shell shopping and may of let go of his original shell to try another on and had his shell taken by another tank mate. This forces the hermit crab to find another shell, if a suitable one isn’t available it is left homeless.
Something may have got into his shell and is irritating his soft abdomen. One can rinse the shell out with dechlorinated water, but many times if something is lodged within the shell this doesn’t help much. Boiling the shell in dechlorinated water and giving it a good shake will many times dislodge anything that may be within it. There maybe pests or a fungus within the shell that is irritating his abdomen and will cause him to leave the shell.
Incorrect environment – too hot, too much or too little humidity
If the hermit crab is too warm, to try to cool off a hermit crab will leave their shells. To prevent over heating it is very important to monitor the substrate temperature as well as the air temperature from the thermometer that is located on the inside tank wall. There is normally a difference of anywhere from a couple degrees to several degrees between the two temperatures readings. The substrate temperature of the warm end of the crabitat should be approximately 78-80 degrees Fahrenheit. (25.555-26.666 Celsius) At 82 degrees F, (27.777) or higher this is getting to be too warm of a temperature for the hermit crab to be comfortable at. There needs to be a cooler side to the substrate as well of (72-73 F (22.22-22.78 C) Hermit crabs are cold blooded creatures and must have the variance of temperatures.
The humidity level is too low in the crabitat and they feel as though they are suffocating. In hopes of relieving the discomfort they are experiencing they leave their shells. If they had been subjected to a too low of a humidity percentage, too many times it has already caused irreversible gill damage. For a more accurate humidity percentage reading level, the humidity gauge should be located close to substrate in the middle of the tank away from water sources that can affect the gauges reading. A relative humidity percentage should be 70-80 percent. Please calibrate your humidity gauge to ensure how accurately it is reading:
A hermit crab will also leave their shell due to a too high of a humidity percentage. A high humidity level makes it difficult for the hermit crab to breath due to the ‘thicknesses’ of the humidity. If subjected to a too high humidity level, this can promote a gill infection that may cause irreversible damage.
And even though it is rare, he maybe in premolt or be molting. Pre molt symptoms
How to gently coax a hermit crab back into their shell
Rinse or boil the shell and shake it to remove anything that maybe lodged within it and tip most of the water out of the shell.
If the hermit crab is not in mid molt, gently pick the hermit crab up and carefully examine the abdomen for any signs of irritation being very careful he does not attempt to escape and injure/kill himself. Examine for any molting symptoms as in transparent eyes, lifting of the old exoskeleton, water sac, etc.
Being very careful and gentle moisten/mist or dip the hermit crabs abdomen with dechlorinated water and try to slide the tip of hermit crabs soft abdomen within his moistened shell making sure it does not scrape or injure the hermit crab. It may be easier to prepare a dish of dechlorinated water, then place both the shell and crab in the water. The buoyancy will make it easier to coax the abdomen into the shell.
If you have tried once or twice to slide the stressed hermit crab into the shell and failed, lower him with the shell into a closed area or isolation unit where the temperature and humidity are within proper ranges. Place the hermit crab next to his shell, with alternate choices of moistened shells to choose from. Attempting any more than twice to get the hermit crab back into a shell he has left very possibly could create him to become even more stressed than he already is. Some owners will place the crab and the shell in a cup together before placing in isolation.
Leave the hermit crab in darkness and quiet for a while and it may return to the shell. If it doesn’t, give the hermit crab a gentle spray mist from a fine mist facial mister bottle with dechlorinated water so that it keeps hydrated if the environment calls for it. Hermit Crabs use modified gills as lungs, so in order to breathe these gills need to be kept moist.
If you need any further help, please read the Emergency Help Article.