Hermit crabs are obsessed with snail shells.

And these crafty little crabs are  more than happy to let the snails do all the work to make their future homes.

In these Northern California tide  pools, turban snails invest years,   sometimes decades, growing their shells.

They pull calcium carbonate  right out of the water to do it.

They spend their days eating the algae that coats pretty much everything in  these rocky, shallow pools.

The rugged shells protect the snails’  squishy bodies from the relentless surf.

They’re way stronger than your  average garden snail shell.

Those sturdy curves catch the attention  of these grainyhand hermit crabs.

But hermit crabs won’t kill  the snails to get them.

They wait for a snail to die and then rush in.

This new home comes with a free meal.

Escargot, anyone?

It’s a competitive market.

And they’re constantly looking to upgrade.

Maybe they’ve outgrown their current place.

A shell that’s too small hampers growth.

And a damaged shell like this one just isn’t safe.

While the front of their body is covered in  stiff armor, their elongated back half is soft.

It curves to match the shell’s spiral shape.

At the very end of its  body, deep inside the shell,   modified legs called uropods grab  on, like the arms of an anchor.

Before they make any big moves, they  usually inspect their new potential digs.

If they like what they see, they make sure the  coast is clear, hold on to both shells, and… Much better, now to get this place cleaned up.

But the crabs never get too attached.

They might occupy this shell for just a  few hours, if they find something better.

Sometimes hermit crabs will squabble  over a particularly desirable abode.

Or bully the current occupant into  abandoning its shell by banging against it.

But the tenant hiding inside won’t give  up its most prized possession easily.

If there’s one thing they can count on,  though, there will always be another shell.

And another, and another, and another.