Why My Hermit Crab Is Eating a Shell

A Hermit Crab and His Shell

• Contrary to their name, hermit crabs aren't hermits---in their natural habitat, the crabs travel in packs of 100 or more. Hermit crabs are actually named for the way they adopt the shells of other animals, mainly those of snails, and carry them around as a means of protection and shelter. Living in large groups makes it easier to find new shells as other crabs trade up.

  A crab usually changes shells after he molts, but sometimes he might just like another shell better. For this reason, it's good to keep a variety of empty shells available in case your crab wants to go house shopping.

The Importance of Calcium

• If you see a hermit crab nibbling on a shell, it's most likely seeking out calcium, which it needs to strengthen its exoskeleton following a molt. Prepared hermit-crab food should contain a calcium supplement, but adding oyster shells or a cuttlebone to the crabitat will help him get the calcium he needs.

  Without enough calcium, weakened exoskeltons will leave a crab open to attack and infections, or a crab may not be able to complete a molt and could perish in the process.

Molting

• Crabs molt about every year to year and a half, depending on its age and living conditions. Crabs have the ability to put off molting if they don't have a way of burying themselves until the process is complete or if they're overstressed.

  Prior to molting, a crab will stock up on fat and water and store it in a "bubble" located just behind its fifth pair of legs. The crab will also crave calcium-rich foods like cuttlebone, sand dollars, sea biscuits or other shells.

  When it's ready to molt, the crab will bury itself in the substrate and remain there until it's finished. The process can take a few weeks to more than a month; even though you may be curious, it's best to leave your crab alone until it's ready to come out on its own.

Diet and Supplements

• Hermit crabs are omnivorous, which means they'll eat just about anything. All food offered should be free of potentially harmful pesticides; use a tap-water conditioner if your water contains chlorine.

  Other foods your crab might enjoy are fruit, vegetables, well-cooked meats (they like to pick meat off of bones), steamed shrimp tails, nuts, cooked eggs, trail mix and applesauce.

Substrate for Your Crabitat

• No need to buy prepackaged "hermit crab sand"; play sand works just as well. Another good substrate is coconut fiber, which is lighter than sand but feels like dirt. Coconut fiber is also conducive to molting as it's easy on a crab's tender new skin.