---
title: "What the sources say about the Common Hermit Crab | AnimalTracks.wiki"
description: "49 claims from the Common Hermit Crab profile, each beside the words of the source that backs it."
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---

# What the sources say about the Common Hermit Crab (*Pagurus bernhardus*)

> 49 claims from the Common Hermit Crab profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Common Hermit Crab](https://animaltracks.wiki/animals/common-hermit-crab/)

## Pagurus bernhardus (common hermit crab). Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Pagurus_bernhardus/

| The page says | The source says |
| :--- | :--- |
| A scavenger | Common hermit crabs are scavengers. (note: tagline) |
| raps on rivals' shells to try to take over better ones | using its chelipeds to rap its opponent's shell (note: tagline; WT: 'The aggressor will knock on the shell it wants, drawing out the owner' (claim below)) |
| to try to take over better ones | Common hermit crabs are more likely to exchange and fight over shells when a new shell confers an advantage, such as more space. (note: tagline; 'better' is ADW's 'confers an advantage') |
| Near-shore waters of northwestern Europe | Common hermit crabs are found in the near-shore North Atlantic waters of northwestern Europe (note: stats.habitat) |
| rocky and shell bottoms, seagrass beds and sand or silt | most types of seabeds, including rocky and shell bottoms, in sea grass beds, and sandy or silty sediments, but excluding muddy bottoms (note: stats.habitat) |
| Scraps of dead animals, plants and microscopic bivalves | microscopic bivalves, scraps of dead animals, and plants (note: stats.diet) |
| The common hermit crab (Pagurus bernhardus) | Pagurus bernhardus (note: body; scientific name only) |
| has a front encased in a carapace of three thick layers | The cephalothorax is encased by a carapace consisting of three thick cuticle layers (note: body) |
| a soft abdomen, the tail end, coiled to the right | The abdomen is soft and coiled to the right (note: body; 'the tail end' is a gloss for 'abdomen') |
| It lives in the abandoned shells of animals such as edible periwinkles and dog whelks | These crabs inhabit the abandoned shells of animals, such as edible periwinkles ( Littorina littorea ), flat periwinkles ( Littorina obtusata ), dog whelks ( Nucella lapillus ) (note: body) |
| Its last two pairs of walking legs are greatly reduced and hold the shell in place | Their last two pairs of walking legs are greatly reduced, and are used to hold the shell in place. (note: body) |
| Animal Diversity Web records a maximum body length of 8 cm | maximum body length 8 cm (note: body; ADW's maximum ('Range length 8 (high) cm'), attributed and kept as a maximum) |
| an average weight of 7.3 g, within a range of 0.13 to 54 g | Range mass 0.13 to 54 g 0.00 to 1.90 oz Average mass 7.3 g (note: body) |
| a shell that is too large does not give the best protection, and one that is too small restricts growth | a shell that is too large does not offer the best protection and a shell that is too small restricts its growth (note: body) |
| Animal Diversity Web says the crab is known to live for up to four years in the wild | Common hermit crabs are known to live for up to four years in the wild. (note: body; attributed to ADW because no current source was found in two searches) |
| Crabs may attack each other to claim a shell | Individuals may attack each other in attempts to claim ownership of a shell. (note: body) |
| they trade visual displays: a crab either raises its body high off the ground or lowers it in submission | Before any physical encounter, Common hermit crabs engage in visual displays. During aggressive encounters, they either raise their bodies high off the ground, displaying their chelipeds and walking legs, or lower their bodies in submission. (note: body) |
| If neither backs down, one crab may crawl onto its opponent's shell and rap on it with its claws | If neither individual submits, the crabs may try to dislodge each other from their shells, an interaction known as shell fighting. One hermit crab will crawl onto its opponent's shell, hitting its opponents entire body, including its shell, and using its chelipeds to rap its opponent's shell (note: body; 'claws' for chelipeds (ADW: 'the first pair are enlarged claws (known as chelae)')) |
| Over 500 raps have been observed in a single shell fight | over 500 raps have been observed in a single encounter (note: blockquote) |
| Around half of these fights end with the attacker swapping shells with its opponent | Around half of such encounters result in the aggressor exchanging shells with its opponent. (note: body) |
| Larger crabs, and those with larger claws, are usually more successful than small and medium ones | Larger crabs, and those with larger chelipeds, are usually more successful than small- and medium-sized crabs in these encounters. (note: body) |
| Shell selection has been extensively studied in this crab | Another behavior that has been extensively studied is shell selection. (note: body) |
| It is able to remember shells it has rejected before | They are also able to remember shells that they have rejected before. (note: body) |
| A crab with no shell, or one in a shell that gives too little protection or space, decides to move very quickly | If a crab is naked or in a shell that does not offer enough protection or space, then it will make the decision to move into a shell very quickly (note: body) |
| from the White Sea to the British Isles, and as far south as Portugal | from the White Sea to the British Isles, including the North, Baltic, and Barents Seas. They are found as far south as Portugal (note: body) |
| It lives on most seabeds, including rocky and shell bottoms, seagrass beds and sandy or silty sediments, but not mud | most types of seabeds, including rocky and shell bottoms, in sea grass beds, and sandy or silty sediments, but excluding muddy bottoms (note: body) |
| It is most often found at depths up to 80 m | Common hermit crabs are most often found at depths up to 80 m (note: body) |
| eating scraps of dead animals, plants and microscopic bivalves | microscopic bivalves, scraps of dead animals, and plants (note: body) |
| it is known to turn cannibal when resources run low | they are known to be cannibalistic when resources are low (note: body) |
| It is nocturnal | Common hermit crabs are nocturnal. (note: body) |
| Not Evaluated | Pagurus bernhardus (note: stats.conservationStatus. Quote only anchors the species name; ADW's 'has not yet been assessed' line is undated and not relied on. GBIF's copy of the Red List returns NOT_EVALUATED (code NE) for Pagurus bernhardus (Linnaeus, 1758), usage key 2224231, ACCEPTED, checked 2026-10-06; Crossref has no IUCN assessment DOI for the name (prefetch and a 10.2305 search 2026-10-06).) |
| it is more likely to swap or fight over shells when a new shell offers an advantage, such as more space | Common hermit crabs are more likely to exchange and fight over shells when a new shell confers an advantage, such as more space. (note: FAQ 1; the FAQ's ref is ADW, so its first sentence now comes from ADW rather than the Wildlife Trusts line the body already uses) |
| Even the final larval stage, which does not feed, has to seek out a suitable shell to complete its change into an adult | Megalops do not eat and must seek out a suitable shell in which to complete metamorphosis. (note: FAQ 1; megalops is the glaucothoe/megalopa stage before adulthood) |
| Over 500 raps have been observed in a single shell fight | over 500 raps have been observed in a single encounter (note: vibe.reason animal clause; same quote as the body claim) |
| weightKg: 0.0073 | Average mass 7.3 g (note: task #1096: 7.3 g = 0.0073 kg, ADW's average mass; Micro class, where the name guess gave Light. Not in a curated matchup) |

## Hermit crab. The Wildlife Trusts.

https://www.wildlifetrusts.org/wildlife-explorer/marine/crustaceans/hermit-crab

| The page says | The source says |
| :--- | :--- |
| lives in an empty sea snail shell | Hermit crabs live inside empty sea snail shells (note: tagline) |
| down to 150 m | They can be found on rocky shores and down to depths of 150m. (note: stats.habitat; the current Wildlife Trusts page (150 m) replaces ADW's older 'may be found as deep as 200 m') |
| Rapping on a rival's shell to try to evict the owner and take its home | When two hermit crabs meet, one may attempt to steal the other's shell by forcibly evicting the current owner. (note: stats.superpower; 'rap' is ADW's word (claim below); 'try to' keeps WT's 'may attempt', since ADW says only around half of shell fights end in an exchange) |
| The Wildlife Trusts give its body length as 3.5 cm | Length of body: 3.5cm (note: body; the current institution page, stated at its own scope) |
| As it grows, it moves into ever larger shells | As they grow, hermit crabs move into ever larger shells. (note: body) |
| The Wildlife Trusts describe the aggressor drawing the owner out and fighting until one emerges victorious | The aggressor will knock on the shell it wants, drawing out the owner and fighting it out until one emerges victorious. (note: body) |
| The Wildlife Trusts record it from rocky shores down to 150 m | They can be found on rocky shores and down to depths of 150m. (note: body; current page replaces ADW's 200 m) |
| It is the largest of several very similar hermit crabs, and it is often found in rockpools | The common hermit crab is the largest of several species of very similar hermit crabs and is often found in rockpools. |
| Look for a reddish brown body and a right-hand pincer that is larger than the left | Their body is reddish brown and right-hand pincer is larger than left. |

## Walsh, Arnott & Kunc (2017). Noise affects resource assessment in an invertebrate. Biology Letters.

https://doi.org/10.1098/rsbl.2017.0098

| The page says | The source says |
| :--- | :--- |
| the crabs approached the shell faster, spent less time investigating it and entered it faster | When exposed to noise, crabs approached the shell faster, spent less time investigating it, and entered it faster. (note: body; abstract only) |
| When researchers exposed crabs to anthropogenic (human-made) noise during shell selection | We experimentally exposed hermit crabs to anthropogenic noise during shell selection. (note: body; abstract only) |

## Crump et al. (2020). Microplastics disrupt hermit crab shell selection. Biology Letters.

https://doi.org/10.1098/rsbl.2020.0030

| The page says | The source says |
| :--- | :--- |
| In one experiment, 64 female crabs were kept for 5 days in tanks with polyethylene spheres or with no plastic | We kept 64 female hermit crabs in tanks containing either polyethylene spheres ( n = 35) or no plastic ( n = 29) for 5 days. (note: FAQ 2) |
| then moved into poor shells and offered a better one | We then transferred subjects into suboptimal shells and placed them in an observation tank with an optimal alternative shell. (note: FAQ 2; abstract only) |
| 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 | they were less likely than controls to contact optimal shells or enter them. They also took longer to contact and enter the optimal shell. (note: FAQ 2; abstract only) |