Hermit Crab
Paguroidea
Quick answer
Hermit crabs are crustaceans that protect their soft, spiraled abdomens by living inside empty snail shells. As they grow, they leave their old shell and move into a larger one, sometimes lining up to swap shells in sequence. Found on shorelines and seabeds worldwide, many species live 10 to 30 years, and they are popular, low-cost pets.
Hermit Crab facts at a glance
| Scientific name | Paguroidea (superfamily) |
|---|---|
| Diet | Omnivore (algae, plankton, scraps, carrion) |
| Habitat | Shorelines, tide pools, and seabeds worldwide |
| Lifespan | 10–30 years (varies by species) |
| Size | From a few millimeters to 30 cm (coconut crab) |
| Top speed | Slow walkers; faster when alarmed |
| Conservation status | Least Concern (IUCN, most species) |
| Kingdom | Animalia |
|---|---|
| Phylum | Arthropoda |
| Class | Malacostraca |
| Order | Decapoda |
| Family | Paguridae |
Borrowed homes
Unlike true crabs, most hermit crabs have a soft, curled abdomen with no hard shell of its own. To protect it, the crab backs into an empty snail shell and carries it everywhere, gripping the inside with specially shaped rear legs. The shell shields the crab from predators and from drying out.
Shell swapping
As a hermit crab grows it outgrows its shell and must find a larger one. When a good empty shell appears, crabs sometimes gather and form a line by size, each moving into the next-biggest shell in a chain swap. Competition for shells can be intense where suitable shells are scarce.
Diet and behavior
Hermit crabs are omnivorous scavengers that feed on algae, plankton, food scraps, and dead animals, helping clean the shoreline. They are mostly active at night and use their antennae and claws to find and handle food. Many species are social and gather in groups, especially around food or fresh shells.
As a pet
Land hermit crabs are common, inexpensive pets that need humid, warm enclosures, a choice of empty shells to grow into, and both fresh and salt water. With good care they can live well over a decade, far longer than many owners expect. They are wild-caught in some regions, so responsible sourcing matters.
Frequently asked questions about the Hermit Crab
Why do hermit crabs live in shells?
Most hermit crabs have a soft, vulnerable abdomen and no shell of their own, so they move into empty snail shells for protection from predators and from drying out.
Do hermit crabs change shells?
Yes. As they grow, hermit crabs must move into larger empty shells. They sometimes gather and line up by size to swap shells in a chain, each taking the next-biggest one.
What do hermit crabs eat?
Hermit crabs are omnivorous scavengers. They eat algae, plankton, food scraps, and dead animals, which makes them useful cleaners of the shoreline.
Are hermit crabs good pets?
Hermit crabs can make low-cost, low-maintenance pets, but they need a warm, humid tank, spare shells to grow into, and both fresh and salt water. With proper care they can live for over a decade.
Are hermit crabs actually crabs?
Hermit crabs are crustaceans closely related to true crabs but in a different group. Unlike true crabs, they have a soft, asymmetrical abdomen that they protect inside a borrowed shell.
