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Hermit Crab Social Behavior – Not Such “Hermits” After All!

Researchers at Tuft’s University and the New England Aquarium have uncovered an amazing example of social behavior among the common pet trade Terrestrial or Land Hermit Crab (Coenobita clypeatus).

Crab Real Estate Markets

Congregation of Hermit Crabs in St. ThomasHermit Crabs protect the soft parts of their bodies by moving into the discarded shells of snails and other creatures.  Finding the right-sized home is a matter of life and death, as shell-less crabs are quickly eaten by predators.  It is also a constant concern for the crabs – as they grow, they need to find increasingly larger shells.

Deprived of shells, the crabs will try anything – one researcher described as “pathetic” their attempts to shelter within bottle caps and pen tops!

One Empty Shell Benefits a Colony

Writing in the May-June edition of Behavioral Ecology, biologists describe a Hermit Crab social behavior that has been coined the “Synchronous Vacancy Chain”.

When a crab finds an overly large shell, it waits nearby rather than moving off in search of a better fit.  Over a period that may span hours, other crabs gather around the shell and, amazingly, line up in size order (largest to smallest), clinging to one another’s shells.  Then, as if a switch were flipped, the largest crab moves into the empty shell, the next largest into the newly vacated shell and so on down the line.  In a few minutes, all the crabs have new, slightly larger homes that will better accommodate them as they grow!  One empty shell thus benefits many rather than a single crab.

Observing and Caring for Hermit Crabs

Hermit CrabI’ve kept Terrestrial Hermit Crabs in group situations, including large zoo exhibits, but have not noticed this behavior, which primarily occurs at night.  This finding really highlights how much we have to learn about even the most commonly kept animals.  Please watch your pets closely (a Night Viewing Bulb may be useful) and write in with your observations; I’ll be sure to share what you learn with other readers.

Hermit Crabs have, potentially, very long lives…but only if given proper care.  Please check out our extensive line of foods, terrariums, heaters, substrates and other Crab Care Products.

Further Reading

To learn more about some of your pet’s lesser known needs, and its fascinating breeding habits, please check out Hermit Crabs: the Need for Salt Water and The Complex Life of a Common Pet.


Hermit Crab image referenced from wikipedia and originally posted by AbsolutDan


  1. avatar

    how do hermite crabs die i dont know how they die mine just fell apart in my cousines hand cry, cry, im sad about that feel bad for me.
    I WANT TO KNOW HOW THEY DIE PLEASE TELL ME HOW THEY DIE i made a grave and burried myne well my brothers hermit crab. cry, cry SABBASTION. … HAD NO NAME REALLY CUZ MY BRO CHANGED IT BUT DID NOT COME UP WITH A NAME TO NAME IT IN ITS LIFE TIME, I MISS MY BROTHERS BABY AKA MINE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    • avatar

      Hello Ashlee, Frank Indiviglio here.

      I’m sorry to hear your bad news. Unfortunately, we do not know very much about why hermit crabs become ill, or how to cure them. However, there are a few things that can be done to help them to stay in good health while they are alive. If you or your brother get another crab, please write back and we can talk about how to care for it.

      Best regards, Frank Indiviglio.

  2. avatar

    Hi, thanks for your information. I love hermit crabs, I post many lovely hermit crabs on my blog. Welcome to check

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for your interest in our blog and glad you enjoyed the info. I look forward to your future comments and enjoyed the photos.

      Good luck and enjoy,

      Best regards, Frank Indiviglio.

About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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