Moving on Up—Hermit Crabs, Vacancy Chains, and the Bigger Picture

by Kristie Lewis

Hermit crabWhen we consider the hermit crab, our minds immediately go to outgrowing shells and finding bigger and better real estate on the beach. Some of us probably think of carnival prizes, nail polished shells, and first pets. In many ways, the hermit crab has become defined by its home in our minds. The creatures’ housing tendencies are what have made hermit crabs unique to us. While many of us consider this trait exclusive to only these small crustaceans, we as humans go through the exact same process.

Last year, I moved to Houston for a job opportunity. I moved into a one bedroom apartment with my husband and we lived in this small space for a year. We then moved to a better area of town into a two bedroom home with a study. In order to move into our first apartment, the person who lived there before us had to move out. They left and created a vacancy, allowing me and my husband to move in. Then when my husband and I moved out of that apartment, we created another vacancy that someone else filled. Likewise, a vacancy had to be made in the newer larger home before we could move in there. Once my husband and I move out of this current house, we will seek a larger house with a yard and the vacancy chain will continue. This vacancy chain is identical to that of the hermit crab.

Now, this process may not sound very spectacular when glossed over in this way. Sure, it’s a logical process—it makes sense that when one living space is vacated, someone else fills it. However, the vacancy chains of hermit crabs and humans are actually very worthwhile and saturated areas of study in sociology and economics. These vacancy chains, when examined carefully, actually communicate elements of similar situations that occur throughout various social systems across many different species. The scientific definition of a vacancy chain is when a resource is exchanged in a sequence from one individual to another and every individual in the sequence benefits from the exchange. These patterns occur in home sales (as my husband and I demonstrated) and they occur when hermit crabs trade out their shell for a newer, shinier one.

When examining the vacancy chain of hermit crabs, we can learn things about our own housing market, car sales, the job market, and so much more. It through this economical process that we can discover motivations behind moves (in living space, job, etc.) and understand what parties benefit from the moves. Researchers have found that in hermit crabs and most other vacancy chains naturally occurring throughout the world, the chain is only beneficial for three individuals or groups. This is a very interesting point. Scientists explain that a higher number of individuals who benefit are only really found in special and very specific situation. Across the board in general, a maximum number of three parties can all benefit from a chain. For things like very high level jobs or extremely large houses, there can be more parties who benefit, but that is a special case. On the other side of the spectrum, the number of individuals who benefit can be lower than three as well. For example, with very low level housing, only one party will benefit at times.

So, those quirky little hermit crabs that we get our children so that they’ll stop asking us for a puppy, actually have a lot to offer the world. We can find great value by just evaluating the simple social system that hermit crabs have become so famous for. The scientific concept of hermit crab vacancy chains has redefined the way in which we examine the job market and people move up in their profession. Rather than focusing on the individual and how to get that individual to move up, we can look at the entire process as a structure and see where that structure can improve to benefit more people. These are really important ideas and practices for today’s society. Those little crabs have a lot to teach us about improving our place on this planet—never underestimate the hermit crab searching for a cozier home.

An expert in the construction industry, freelance writer Kristie Lewis offers tips and advice on choosing the best construction management colleges. She welcomes any questions and comments you might have at

Hermit crab photo via Shutterstock

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