Lots of animals build homes for protection—think beaver lodges or termite mounds. Hermit crabs, on the other hand, inhabit hand-me-down homes. But they remodel them first, carving out shells to make them lighter and twice as spacious as the originals. Those creature comforts come at a cost, though—because hollowed-out shells can be more easily crushed in the jaws of a predator.

Researchers wanted to find out if hermit crabs take that crucial detail into consideration. So they gave over a thousand new sea snail shells to hermit crabs in Costa Rica. A year later they recovered the used ones. Then they crushed them.

As expected, remodeled shells broke twice as easily as new ones. But the strength it took to smash them was still just a bit more than local raccoons can muster—meaning crabs may remodel with their predator's bite in mind. The results are in the Journal of the Royal Society Interface. [Mark E. Laidre, Eli Patten and Lisa Pruitt, Costs of a more spacious home after remodelling by hermit crabs]

The benefits of the fixer-upper larger home are many: females lay more eggs, males grow burlier and crabs can avoid nasty squabbles with competitors for a real estate upgrade. And they don’t even have to shell out much.

—Christopher Intagliata

[The above text is a transcript of this podcast.]