The house-hunter Hermit Crab

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Hermit crabs live in shells discarded by sea snails that have died. However, they may pull out the live snail, getting a new house and a feast as well. Hermit crabs don’t live in the same shell all their lives; they replace their ‘borrowed’ shell as they moult and grow. Larger animals most often inhabit Campanile shells, while juveniles utilise a number of different smaller shells. To find a new shell, they line up next to it and quickly move from the old home into the new home. Due to its soft abdomen, hermit crabs are very vulnerable to being eaten and hence this is the only time they will leave their shell.

Hermit crabs, like other crabs are scavengers. This means they will eat just about anything, but typically feed on seaweed or dead animal matter. They use their strong nippers to tear apart their food and place it into their mouth. Hermit crabs use their legs and front claws to drag themselves across the reef and the sea floor.

To reproduce, the separate sexes release eggs and sperm into the water column. The eggs and sperm meet by chance in the water column and fertilisation occurs. The fertilised egg becomes part of the plankton for some time before it is big enough to swim against the currents.

Threats include; human disturbance (removing shells from beaches) and pollution.

Conservation Status

The waters around Rottnest Island are a designated Marine Reserve. Some parts of Rottnest’ coral reefs are included the Marine Sanctuary Zones shown in the Rottnest Island Marine Management Strategy (2007).

  • Extinct
  • Extinct in Wild
  • Critically Endangered
  • Endangered
  • Vulnerable
  • Near Threatened
  • Least Concerned

Help keep Rottnest’s beaches and reefs healthy

  • Do Not remove or collect shells from the Island's beaches
  • Do anchor only in sandy areas of water
  • Do take litter with you or use bins provided
  • Do collect fishing line if seen in ocean or on shores