---
title: "Common Hermit Crab (Pagurus bernhardus) | AnimalTracks.wiki"
description: "A scavenger that lives in an empty sea snail shell and raps on rivals' shells to try to take over better ones."
image: "https://animaltracks.wiki/images/animals/common-hermit-crab-1.webp"
published: "2026-10-09"
updated: "2026-10-09"
---
# Common Hermit Crab (*Pagurus bernhardus*)
> **Status**: Checked against 4 sources, listed under Sources below.
> **Tagline**: A scavenger that lives in an empty sea snail shell and raps on rivals' shells to try to take over better ones.
> **Soundtrack Vibe**: Classic Funk, Soul & Disco // The Winstons, "Amen, Brother"
> **Soundtrack Links**: [Spotify](https://open.spotify.com/track/32Rf95ZT8gxisQMK6xAhba)
> **Vibe Match**: Over 500 raps have been observed in a single shell fight, as one hermit crab knocks on another's shell. "Amen, Brother" stops for a solo drum break: a few bars of hard, rapid knocking.
## Biological Superpowers & Stats
- **Taxonomy**: *Pagurus bernhardus*
- **Danger Level**: Low
- **Conservation Status**: Not Evaluated ([IUCN Red List](https://www.iucnredlist.org/))
- **Superpower**: Rapping on a rival's shell to try to evict the owner and take its home
- **Habitat**: Near-shore waters of northwestern Europe on rocky and shell bottoms, seagrass beds and sand or silt, down to 150 m
- **Diet**: Scraps of dead animals, plants and microscopic bivalves
- **Tags**: crustacean, ocean, tide-pool, benthic, scavenger, omnivore
## Natural History & Behavior
## A soft body in a borrowed home
The **common hermit crab** (*Pagurus bernhardus*) has a front encased in a carapace of three thick layers and a soft abdomen, the tail end, coiled to the right. It lives in the abandoned shells of animals such as edible periwinkles and dog whelks. Its last two pairs of walking legs are greatly reduced and hold the shell in place.
The Wildlife Trusts give its body length as 3.5 cm. Animal Diversity Web records a maximum body length of 8 cm and an average weight of 7.3 g, within a range of 0.13 to 54 g. As it grows, it moves into ever larger shells. The fit matters: a shell that is too large does not give the best protection, and one that is too small restricts growth. Animal Diversity Web says the crab is known to live for up to four years in the wild.
## Knock, knock, get out
Crabs may attack each other to claim a shell. Before any physical fight, they trade visual displays: a crab either raises its body high off the ground or lowers it in submission. If neither backs down, one crab may crawl onto its opponent's shell and rap on it with its claws. The Wildlife Trusts describe the aggressor drawing the owner out and fighting until one emerges victorious.
> **Rap battle** Over 500 raps have been observed in a single shell fight.
Around half of these fights end with the attacker swapping shells with its opponent. Larger crabs, and those with larger claws, are usually more successful than small and medium ones.
## A fussy house hunter
Shell selection has been extensively studied in this crab. It is able to remember shells it has rejected before. A crab with no shell, or one in a shell that gives too little protection or space, decides to move very quickly.
When researchers exposed crabs to anthropogenic (human-made) noise during shell selection, the crabs approached the shell faster, spent less time investigating it and entered it faster.
## Scavenger of the northeast Atlantic
This crab lives in the near-shore North Atlantic waters of northwestern Europe, from the White Sea to the British Isles, and as far south as Portugal. It lives on most seabeds, including rocky and shell bottoms, seagrass beds and sandy or silty sediments, but not mud. It is most often found at depths up to 80 m, and The Wildlife Trusts record it from rocky shores down to 150 m.
It is a scavenger, eating scraps of dead animals, plants and microscopic bivalves, and it is known to turn cannibal when resources run low. It is nocturnal.
## Frequently Asked Questions
### What does a hermit crab do when it outgrows its shell?
It looks for a roomier one, and it is more likely to swap or fight over shells when a new shell offers an advantage, such as more space. Even the final larval stage, which does not feed, has to seek out a suitable shell to complete its change into an adult. *(Source: [Animal Diversity Web, University of Michigan]())*
### Can plastic pollution affect hermit crabs?
In one experiment, 64 female crabs were kept for 5 days in tanks with polyethylene spheres or with no plastic, then moved into poor shells and offered a better one. Crabs that had been with plastic were less likely to contact the better shell or enter it, and took longer to contact and enter it. *(Source: [Crump et al. 2020]())*
### How can you tell a common hermit crab from its relatives?
It is the largest of several very similar hermit crabs, and it is often found in rockpools. Look for a reddish brown body and a right-hand pincer that is larger than the left. *(Source: [The Wildlife Trusts]())*
## Sources
1. [Pagurus bernhardus (common hermit crab). Animal Diversity Web, University of Michigan.]()
2. [Hermit crab. The Wildlife Trusts.]()
3. [Walsh, Arnott & Kunc (2017). Noise affects resource assessment in an invertebrate. Biology Letters.]()
4. [Crump et al. (2020). Microplastics disrupt hermit crab shell selection. Biology Letters.]()
*Published October 9, 2026. Last updated October 9, 2026.*
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