These Feisty Hermit Crabs Brawl Over Snail Shells | Deep Look

From Deep Look.

Hermit crabs are *obsessed* with snail shells. These crafty little crabs, found in California’s rocky intertidal zone, are more than happy to let the snails build them a perfect home. When the crabs find a snail shell they like, they hop right into their new abode.

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DEEP LOOK is an ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Explore big scientific mysteries by going incredibly small.


Hermit crabs are one of the most recognizable and adored inhabitants of tide pools. But they aren’t just cute (for a crab).

“They’re one of the most important creatures in the intertidal zone because of their role as scavengers,” said Stephen Dunbar, a professor of biology at Loma Linda University. “They begin the process of cleaning up dead materials, like dead seaweed, fish, crabs, snails or whatever else.”

While hermit crabs scavenge for food, they also keep an eye out for new shells to call home.

Grainyhand hermit crabs seem to prefer turban snail shells. That’s good because turban snails are incredibly abundant in the intertidal zone. The snails can spend 20 years growing and building their shells as they graze on the algae that grows all over the rocks.

— What do hermit crabs eat?
Hermit crabs are scavengers. They eat decaying plants and algae in addition to dead animals.

— How do hermit crabs mate?
When it’s time for hermit crabs to mate they leave their shells briefly, mate, and then return to their shells. They are vulnerable outside of their shells so they do so quickly.

— Why do hermit crabs need shells?
Hermit crabs have stiff armored shells to protect their head, claws and walking legs. The back half of the hermit crab’s body, including it’s long curved abdomen, is soft to better fit inside a snail’s spiral-shaped shell. Without a snail shell to protect it, a hermit crab is vulnerable to predators.

—+ Find additional resources and a transcript on KQED Science:

https://www.kqed.org/science/1975024/watch-these-hermit-crabs-shop-for-the-perfect-shell

—+ More great Deep Look episodes:

For Pacific Mole Crabs It’s Dig or Die | Deep Look
https://youtu.be/tfoYD8pAsMw

Decorator Crabs Make High Fashion at Low Tide | Deep Look
https://youtu.be/OwQcv7TyX04

Whack! Jab! Crack! It’s a Blackback Land Crab Smackdown | Deep Look
https://youtu.be/KBMUhG0aEFg

—+ Shoutout!

🏆Congratulations🏆 to the following 5 fans on our Deep Look Community Tab for identifying the specially modified limbs hermit crabs use to grip their shells – urupods!

Lucas
Octo Valley
Sarmad Nasim
Harry To
Akash Chaturvedi

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