Why Do Hermit Crab Legs Fall Off?

Ringshark - Hermit Crab
Lianne McLeod

On occasion, hermit crabs will lose their legs (including their claws) and they can be grown back during subsequent molts. However, losing legs can also be related to stress from various other things. Therefore, if you have a hermit crab that is losing their legs you should make sure there are no problems with them before assuming the legs will grow back. While losing a limb is not a death sentence for a crab, it is still usually an indication of some sort of problem that needs attention immediately. At the first sign of leg loss make sure none of the following problems exist to prevent further problems with your crabs.

Poor Tank Conditions Cause Hermit Crab Legs to Fall Off

  • Make sure the humidity in your crab's home is at 70-80 percent relative humidity. If the environment is too warm it can cause a problem as can it being too dry for a hermit crab. Purchase a hygrometer to be able to monitor this easily and accurately.
  • Check the temperature in the enclosure. Make sure it isn't too high or too low, has hot spots and that there isn't too much fluctuation during the day and at night. Aim for temperatures between 72-78 degrees Fahrenheit (22-26 degrees Celsius).
  • Make sure there is no chlorine in the water in the tank by using a de-chlorinator. This liquid can be purchased at any pet store that carries fish supplies and is simply added to your hermit crab's water.
  • Be careful with residual chemicals from cleaning in or around the tank. Try to use only hot water for cleaning your hermit crab tank.
  • Check the condition of the substrate. Make sure it isn't too damp and that there is no mold. Clean the tank regularly to remove any waste matter and/or uneaten food.
  • Do not bathe your hermit crab too often. Once a week is plenty under most conditions.

    Mites Cause Hermit Crab Legs to Fall Off

    • Check the tank and crabs for mites. Mites will appear as tiny specks moving around. Hold your crab up by the shell until they extend themselves outside of the shell some (blow gently on the crab to entice them out if necessary) and inspect their body for mites. If you think your crabs and tank have mites be sure to boil everything in the tank in hot water (not the crabs, of course), wipe the tank with vinegar, and bathe your crabs with Stress Coat (purchased from the aquarium department in the pet store until you no longer see any mites.

    Injuries Cause Hermit Crab Legs to Fall Off

    • Hermit crabs are usually pretty peaceful but sometimes they will fight over resources, especially coveted shells. If your crabs are fighting over shells, you need to increase the number of appropriately sized shells in a variety of styles to make sure there is enough of a selection to stop the fighting.
    • Consider larger tanks, more hiding places, and more food and water bowls if your crabs are fighting. If the problem persists, you might want to separate the crabs.

    Illness and Severe Stress Cause Hermit Crab Legs to Fall Off

    • If you have a hermit crab that lives with other hermit crabs that is very stressed or ill, multiple legs may fall off. If your hermit crab has lost more than one leg in a short period of time, isolate them from the other hermit crabs while still maintaining proper conditions, especially the temperature and humidity. The cause for the legs to fall off is not usually contagious to other crabs but this will help keep your crab comfortable and free from the stress of competing with other crabs. Crabs that drop multiple legs are often so stressed that they cannot be saved, unfortunately.
    • Sometimes new crabs have legs that fall off shortly after you get them home. This is more likely due to the conditions they experienced during collection, shipping, and during their time at the pet store rather than anything you are doing. Just make sure your hermit crab environmental conditions are ideal and hope that the stress reaction is reversible now that your crabs are being properly cared for.

    Do Hermit Crab Legs Grow Back?

    Usually, if a hermit crab leg falls off it will regenerate, or grow back, that lost leg. At first, a "gel limb" forms which start out as a little bud or bump. This gel limb develops over the course of a few molts into a new leg (or claw) though it may be smaller than the original one. Your crab may undergo more frequent molts until this limb has been completely regenerated.​​