The hairy hermit crab grows to 0.8” and is commonly found in a shell that seems to barely fit! You’ll know it is a hairy hermit crab if it has banded brownish and white antennae, and white bands that encircle the outer joints of its second and third walking legs. Each walking leg usually has 1 or 2 blue dots and its body has numerous small hairs. The right claw is larger than the left and is mainly used in defense. The smaller left claw is used for eating and selecting new shells.
Habitat
Intertidal zone to depths of ~360’ (110 m). Rocky areas, tidepools, silty areas.
Diet
Mainly detritus, seaweeds
Life History
A hairy hermit crab male deposits sperm near the female’s abdomen. She stores it until she lays her eggs, then fertilizes them. She begins brooding in late fall, carrying the eggs inside the shell, on the left side, with larvae hatching around February. Most females carry 5 broods a year through the spring and summer months. A single brood can have up to 660 eggs, with larger females laying more eggs.
IUCN Status
Not Evaluated
Ecosystem & Cultural Importance
As a detritivore, these crabs cycle nutrients from dead plants and animals back into the ecosystem. They also serve as food for their predators, which includes sculpins and other crabs.
Hermit crabs do not make their shells but take those of snails that have died. Some favorite snail shells of the hairy hermit crab are the frilled dogwinkle (Nucella lamellosa), dire whelk (Searlesia dira), periwinkles (Littorina genus), and purple olive shells (Callianax biplicata). In selecting a shell, a hairy hermit crab will examine it using its left claw, as the hairs on this claw are able to detect calcium. Many hairy hermit crabs will carry shells that they can’t completely withdraw into. If need be, they will drop their shell and use speed to outrun a predator.
Citations & Other Resources
Arthropod Page of Netarts Bay Today: https://www.netartsbaytoday.org/Arthropods_Text.html#LayoutGrid36
Biodiversity of the Central Coast website: https://www.centralcoastbiodiversity.org/hairy-hermit-crab-bull-pagurus-hirsutiusculus.html
Evergreen College website: https://archives.evergreen.edu/webpages/curricular/2007-2008/ize/web/pagurus_hirsutiusculus.html
Invertebrates of the Salish Sea website: https://inverts.wallawalla.edu/Arthropoda/Crustacea/Malacostraca/Eumalacostraca/Eucarida/Decapoda/Anomura/Family_Paguridae/Pagurus_hirsutiusculus.html
Scholar’s bank website: https://scholarsbank.uoregon.edu/xmlui/bitstream/handle/1794/12728/P_hirsutiusculus_2015_final.pdf?sequence=3&isAllowed=y
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