Hermit crabs don't build their own shells. They are scavengers and find empty shells left behind by other sea creatures, like snails.
Here's why they need shells:
* Protection: Their soft abdomens are vulnerable to predators, so they rely on empty shells for protection.
* Home: The shell provides a safe place to hide and rest.
* Camouflage: The shells help them blend in with their surroundings.
As hermit crabs grow, they need to find bigger shells. They often swap shells with other crabs or find empty ones along the ocean floor.