Here’s How Hermit Crabs Swap Shells Like It’s Nothing

Hermit crabs are fascinating. Not only do these crustaceans often grow into massive creatures, but they also change shells throughout their lives. Their appearance can vary depending on the size and shape of shells they choose during molting. In this Instagram video, you can watch a hermit crab hoist itself out of its old shell and into a new one with ease. Let’s learn more about why they do this unusual home relocation behavior.

Why Do Hermit Crabs Change Shells?

A hermit crab will change shells once it outgrows the current one it’s inhabiting. During a process called molting, which typically occurs once every 12 to 18 months for adult hermit crabs, but more frequently for juveniles, the animal sheds its calcium-rich exoskeleton and eats it. It then begins to develop a new and soft exterior. From there, it will find a new, larger shell to accommodate its increased size.

A hermit crab’s shell is a source of protection, especially for the animal’s soft abdomen. Some crabs can be pickier than others when selecting their temporary home. If the shell is uncomfortable, they’ll often change before it’s necessary. Additionally, many of these little guys have commitment issues of sorts. In other words, they’d rather explore their shell options instead of sticking with just one for an extended time.

How Do They Change Their Shells?

Hermit crabs typically take over the abandoned shells of sea snails. They’re often attracted to the smell, size, and comfort level of certain shells. Once a hermit crab finds a shell it likes, it will ensure it’s the correct fit before transferring itself. The animal will then pull itself out of the old shell using its front legs/claws before hoisting its abdomen into the new shell. During this process, the crab essentially backs itself into the new shell, abdomen first. You can witness this in the Instagram video linked above. 

Hermit Crabs vs. Other Crabs

Despite their name, hermit crabs are not actually crabs at all. They are, however, crustaceans. Unlike real crabs, which don’t need a protective shell, hermit crabs have soft and vulnerable abdomens. True crabs already have a hard exterior that protects their bodies.