Hermit crab (common)
Pagurus bernhardus
IUCN Status:Least Concern
A favourite rock pool sight, these 'borrowers' are highly social.
What do they look like?
Easily spotted by their spiral or snail-like shell, hermit crabs typically have red/orange legs, beady pale eyes and long antennae for sensing their surroundings. Hermit crabs have a longer set for feeling and a shorter set for smell and taste.
Where can they be found?
In pools, on sand, amongst seaweeds, in the shallows and at depth. All around UK & Ireland
Did you know... Hermit crabs communicate by chirping - their high pitched chirps sound like a bit like a frog.
Key facts
The most striking thing about a hermit crab is its home; usually an empty snail shell. Because their bodies are soft and curled, they fit perfectly inside these spiral-shaped shells, which protect them from predators.
If you offer a few empty shells in a shallow pool and wait patiently, you might be lucky enough to watch a hermit crab switch homes. They inspect each shell carefully before making the move.
Hermit crabs moult their exoskeleton as they grow, and each time they get bigger, they need to upgrade to a larger shell. Sometimes, if a crab spots a neighbour with a particularly desirable shell, it may try to steal it. The would‑be thief taps or “knocks” on the shell to lure the owner out, and the two may tussle until one ends up victorious.
Despite their name, hermit crabs are far from solitary. They dislike being alone and often live in bustling colonies of 100 individuals or more, and rely on one another for safety and social interaction.
| IUCN status | Least Concern |
|---|---|
| Length | 2-5cm (without shell) |
| Weight | 20-80g (without shell) |
| Speed and distance | Slow and steady wins the race, as the saying goes - hermit crabs can move approximately 2 metres per hour. |
| Habitat | Rocky shore, lower shore, subtidal, seabed, rock pools. |
| Diet | Anything they can find, including seaweed, worms, alga, detritus and decaying matter - yummy! |
| Age lifespan | Small but mighty, hermit crabs in the wild can live up to a whopping 40 years old. |
