A hermit crab lives in a borrowed seashell.
When it gets bigger, it moves into a bigger shell.
There are lots of different kinds of hermit crabs.
Some live in the sea.
Some live on land and make good pets.
A hermit is the name given to a person who avoids being with other people. Hundreds of years ago, hermits moved far away from where people lived. Often a hermit would live in a cave on a mountain.
Hermit crabs got their name because they live in a cave-like shell, like the old hermits who lived in mountain caves. That is the only resemblance, because hermit crabs are actually very social creatures and don't avoid each other.
Hermit crabs are not closely related to true crabs. There are about 500 different kinds of hermit crab in the world. Some live in deep sea water, some in shallow coral reefs and beaches, and some are quite large. One kind that lives in the Caribbean islands climbs trees. In warm places there are many kinds of hermit crabs that are terrestrial, or land-living.
Hermit crabs are in the group of animals called crustaceans (say crus-tay-shun). They have an exoskeleton, which means their outside is a hard shell and they don't have bones inside their body. However, the exoskeleton over the abdomen is quite soft, which makes them easy prey for other animals. They protect their abdomens by moving into and carrying around an empty seashell. The tip of their abdomen clasps strongly onto the centre of the spiral part of the shell. When the hermit crab grows too big for the borrowed shell, it has to move into a larger one. The shell also stores water for the crab because their gills need to be kept moist in order for them to breathe. If the gills dry out, the animal will gradually die.
Hermit crabs have jointed legs. Their eyes are on stalks and they have two sets of antennae. They are nocturnal, which means they are active at night. They are omnivores, which means they eat plants as well as meat.
Several kinds of small land-living hermit crabs are the ones that people can keep as pets. They are cute, but they are not as easy care as people think. It is difficult to keep them healthy. It is better to have several, because they shouldn't be kept alone as they are social animals.
Hermit crabs as pets
Housing pet hermit crabs
Before you buy your hermit crabs, you must have a home ready for them.
Pet hermit crabs do not need huge homes, but the correct temperature and humidity is essential for their health and wellbeing. Terrestrial, or land, hermit crabs come from warm places so they need to be kept warm. Glass or plastic fish tanks with lids can be adapted to make a home for hermit crabs. The lid helps keep the air inside warm and moist, which is important so they don't suffocate.
The tank should be big enough for them to move around. There must be a layer of material on the bottom of the tank. This is called substrate. Make a thick layer of sand on the bottom of the tank, because hermit crabs like to burrow into it. The sort of sand that is used in a sandpit is good, or you can buy aquarium sand. Do not use builder's sand, or gravel or wood shavings.
Correct temperature is important.
Hermit crabs do best if the temperature is around 22-27ºC. If it is cooler than this for long periods of time, they can become ill. A special lamp can be used at one end of the tank so there is a warm zone and a cooler zone. Keep a thermometer in the tank. With warmth and a solid lid on the tank, a water dish should be enough to create humidity. It is also possible to put a sea sponge in a dish of filtered water for extra humidity. However, you do not need too much humidity or fungus will grow inside the tank.
Pieces of driftwood or other wood, or coral, in the tank provides obstacles for the hermit crabs to climb on.
Feeding your pet hermit crab
There are commercial dry foods available in pet shops for hermit crabs. Any uneaten food in the food dish should be removed each day. In addition, feed your pets fresh foods including: mango; papaya or pawpaw; coconut (fresh or dried); strawberries; bananas; apples; pineapple; grapes; carrots; leafy green lettuces (not iceberg lettuce); melon; spinach; watercress; broccoli; grass; freeze dried shrimp (from the fish food section at the pet shop); leaves and strips of bark from deciduous trees (not conifers); brine shrimp; fish food flakes.
Hermit crabs need calcium so cuttlefish bone (from the bird section of a pet shop) can be given whole or scraped and added to their food dish. You could also add crushed shell grit, also from the bird section, or crushed egg shells to the food dish.
Fresh water is needed for drinking. Use filtered water or rainwater so there is no chlorine in it. A larger dish of salt water can be provided for the hermit crabs to get into. Do not use table salt. Saltwater can be found in an aquarium shop that sells saltwater fish. Shallow, strong and easy-to-clean dishes are used for food and water containers, and a larger one for saltwater.
Responsible pet ownership
Pet hermit crabs depend on their owners for food, protection and shelter. Before becoming a pet owner think carefully about all the things you will have to do to care for your pet responsibly.