Everyone wants a home for the holidays — including hermit crabs. And now, after weeks of frustration, a group of Brooklyn-based entrepreneurs finally seem to be making headway in their quest to end the hermit crab housing crisis.

The folks behind Project Shellter, a side project for 3-D printer company MakerBot Industries, have spent much of 2011 working on a campaign to design and produce synthetic shells for hermit crabs. They're using MakerBot's Thing-O-Matic, a 3-D printer that carves plastic models from digital blueprints, but they're soliciting those blueprints from people around the planet.

This crowd-sourced strategy is aimed at generating successful, and interesting, designs as quickly as possible. But even though the designs so far have been largely based on the sea snails whose shells are preferred by hermit crabs, the effort hasn't been very successful. At least not until recently.

First, a little background: Hermit crabs can't make their own shells, so they scavenge whatever home they can find. They prefer certain sea-snail shells, and even partake in complex social behavior to make sure everyone has a well-fitting shell. But people also like to collect those seashells from beaches, leaving some terrestrial hermit crab species with fewer and fewer housing options. They can improvise with manmade objects like beer bottles or shotgun shells, but those typically don't work as well.

Throw in the effects of ocean acidification — which also weakens the calcium carbonate shells of marine organisms — and many hermit crabs are in dire straits.

And that's where Project Shellter comes in. The group has been testing various shell designs among hermit crabs living in its Brooklyn "crabitat" for several weeks, but the crabs just stubbornly ignored the Thing-O-Matic's offerings. On Dec. 7, however, after nearly two months of experimentation, a crab named "Kendall Karshellian" adopted one of the printed plastic shells. It was based on the shells of Oxystele sinensis sea snails, and it was followed by another success on Dec. 13. That's when "Kylie Karshellian" jumped on the bandwagon and tried on a printed shell for herself.

Hermit crabs tend to shop around for shells, often trying them on and taking them off multiple times. But the crabs at Project Shellter "seem happy" in their printed shells, according to project designer Miles Lightwood, and are wearing them around the crabitat like normal shells. If this continues, Project Shellter may be on a path for mass production. The organizers say they have no plans to distribute plastic shells on beaches for wild hermit crabs, though — their goal is to provide ideal synthetic shells for pet hermit crabs, offsetting the need for people to collect real shells from beaches.

Everything the Thing-O-Matic produces is currently made of plastic, which isn't the most eco-friendly substance, but it may be the lesser of two evils if it can save homeless crabs. Plus, while the final shell material is yet to be determined, Lightwood says biodegradable polyactic acid is being considered alongside traditional plastic.

Here's a video showing the first successful adoption of a Thing-O-Matic shell:

Russell McLendon ( @russmclendon ) writes about humans and other wildlife.

Progress made in hermit-crab housing crisis
A project to save hermit crabs with crowd-sourced, 3-D printed shells has its first major success: Crabs are finally using the manmade shells.