Hermit crabs protect their rear ends by hiding it in a snail shell.
There are many species of hermit crabs ranging from Alaska to Mexico. Although usually found in tide pools, they can also be found at depths of up to 50 feet. Hermit crabs feed on plant debris and are such effective scavengers that they have been described as the garbage collectors of the intertidal zone. They are also an important food source for fish including pile perch.
Hermit crabs use empty snail shells as protection into which they will retreat quickly if bothered. As the hermit crab grows, it is necessary for it to find larger snail shells. They do not kill snails for their shells, but larger hermit crabs have been know to evict smaller hermit crabs from a shell. Hermit crabs inspect prospective shells very thoroughly before changing shells. Because hermit crabs cannot always find a readily available and suitable shell, anything hollow is sometimes used until they find something better. The tail appendages of the hermit crab are modified into hooklike structures that cling to the shell so firmly that a hermit crab will nearly always allow itself to be split in two before it can be pulled out of a shell. It is always best to gently handle and then return all animals and shells to the tidepools.
Hermit crabs are usually found at the Aquarium in tank numbers 1, 3 and 9.