What are Hermit Crabs?

Harvesting of gastropods.
Harvesting of gastropods.

A hermit crab is a small crustacean that belongs to the phylum of arthropods. With about 1,400 known species, hermit crabs live either on land, in intertidal areas, or in both deep and shallow waters of the oceans. They are found virtually all over the world, from the tropics to the arctic. The name hermit crab is somewhat of a misnomer, as hermit crabs are social animals that usually travel in large groups.

Hermit crabs use the shells of other animals as their home.
Hermit crabs use the shells of other animals as their home.

The most distinctive characteristic of a hermit crab is that it uses the shell of another animal as its home. Most appropriate are the shells of gastropods, usually snails. The hermit crab is not aggressive, and therefore will usually not attack a living snail for its shell unless it is ill. The hermit crab prefers shells that are already vacated.

Unfortunately, some hermit crabs take advantage of manmade objects that pollute the oceans and beaches to make their home. Hermit crabs have been seen dwelling in small jars, plastic casings, or any other refuse that will make do. Experts believe that this behavior is the result of a decline in available gastropod shells. They believe that pollution is causing a decline in the snail population that, along with the practice of collecting seashells, forces the hermit crab to reside in manmade materials.

A hermit crab cannot stay in the same shell forever. The biggest reason that a hermit crab must seek out other shells is because it grows larger, and obviously, the shell doesn’t. When shells are available, many hermit crabs switch shells frequently in their search for the ultimate fit. A hermit crab rarely leaves its shell, but must do so on occasion in order to mate, molt, or move into a new shell.

Hermit crabs use shells because they have an extremely soft abdomen that requires protection from predators. The visible part of the hermit crab consists of a hard exoskeleton, one very large claw that is used for breaking up food and for defense and another relatively small claw used for eating. Both claws assist the hermit crab in its avid climbing. The concealed part of the hermit crab's body has tiny legs that enable it to move when out of its shell and assist in anchoring its body when inside the shell.

Hermit crabs have become a popular pet that is frequently sold or won at seaside boardwalks. They are unfortunately viewed by many as low maintenance, throw-away pets, replacing the traditional carnival goldfish. It is nearly impossible to breed hermit crabs in captivity, as they require the sea to deposit their eggs. For this reason, pet stores and boardwalks must obtain their hermit crabs directly from the wild.

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Discussion Comments


@calabama71: Hermit crabs will eat a large variety of foods. In their natural habitat, they are scavengers, eating just about anything that they can find. They love lettuce, fruits, and vegetables. They have even been known to enjoy peanut butter. Some “table scraps” are actually good for your hermit crab because they can contain sea salts that are beneficial to their diet.

Fresh water for drinking is very important for the crab. You can use a small container for water. Be careful not to use one that is deep because the hermit crab can fall in and drown. Some people use scallop type seashells for a “drinking bowl”. They will also drink water from the wet sponge that you put in their cage.


@calabama71: You can buy a regular fish aquarium to keep your pet hermit crab in. The most important aspect of caring for a hermit crab is making sure that it maintains moisture. Hermit crabs live on land but they breathe through gills. For that to happen, they must remain moist.

To maintain moisture, you can put a natural sponge in the aquarium with the hermit crab and make sure it is always moist. The crab will spend much of their time hidden under the sponge.


My son wants a hermit crab for a pet but I have no idea how to care for one. Is there such a thing as a hermit crab aquarium? What do they eat?

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    • Harvesting of gastropods.
      By: papinou
      Harvesting of gastropods.
    • Hermit crabs use the shells of other animals as their home.
      By: haveseen
      Hermit crabs use the shells of other animals as their home.