Why Is Your Hermit Crab Losing Legs?

Ringshark - Hermit Crab
Ringshark - Hermit Crab. 2006 Lianne McLeod, Licensed to About.com, Inc.

Help! My Hermit Crab is Losing Legs! What Can I Do?

This is a common question new hermit crab owners ask. Hermit crabs will normally sometimes 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 improper living conditions (temperatures, humidity, cleanliness, etc.) so if you have a hermit crab that is losing legs you should rule out any problems in their environment before assuming they will grow back.

Other reasons for leg loss include aggression from other crabs, mite infestations, wounds, or illnesses. 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.

Incorrect Tank Conditions

  • 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. Purchase a hygrometer to be able to monitor this.
  • 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. Use a dechlorinator on all water in the tank. This liquid can be purchased at any pet store that carries fish supplies.
  • 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.
  • This should be a given for any pet but the cleanliness of the tank is important. Clean the tank regularly to remove any waste matter and/or uneaten food.
  • Do not bathe your crab too often. Once a week is plenty under most conditions.

Mites

  • ​Check the tank and crabs for mites which will appear as tiny specks moving around. Hold your crab up by the shell until your crab extends himself outside of the shell some (blow gently on the crab to entice him or her out if necessary) and inspect their body for mites. If you think your crabs and tank have mites be sure to 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 and is used to help protect the slime coat of fish) until you no longer see any mites.

Injuries

  • 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.
  • You might also want to 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

  • If you have a crab that is very stressed or ill they may drop multiple legs. If your hermit crabs have lost more than one leg in a short period of time, isolate the crab (still maintaining proper conditions, especially the temperature and humidity). The cause of the legs dropping is not usually contagious, 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.
  • Sometimes new crabs start dropping legs 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.

Will The Legs Grow Back?

Usually the dropped leg will be regenerated. At first a "gel limb" forms which starts 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. Your crab may undergo more frequent molts until the limb has been regenerated.

Edited by Adrienne Kruzer, RVT