How Do Hermit Crabs Change Shells?

There are certainly a lot of hermit crabs in Guadeloupe. You find them not only on beaches but on rocks close to the road or even in villages. At first, you notice their presence by a shell moving on the ground. Depending on the species Hermit Crabs exchange their home about two times a year with growth. They molt every 12-18 months in need to exchange their shell before and after. ¹ Not every shell is suitable to be the new mansion. So how do hermit crabs manage to find the perfect fit? 

How do hermit craps change shells? 

The truth is really surprising. These animals hold a ceremony that resembles the children´s game musical chairs. Hermit Crabs that require a bigger home align themselves in a queue to receive a new shell from each other. This swapping is triggered by the most giant crab moving in into a new shell found on the beach. Afterward, everyone quickly proceeds into the shell abandoned by the crab in front of them. If outsiders join this exchange in the interim it becomes more difficult for other crabs to find one shell with the perfect size. When you are the person without a seat in musical chairs the only disadvantage for you is a disappointment. Different than that a hermit crab that doesn´t find a suitable home is punished hardly with its life. The losers can´t survive long without a shell. ²

Apart from this ceremony, hermit crabs do not exchange their shell in this manner every time. The Caribbean Hermit Crab also abandons its home, when it finds a better by hazard. Some species as the Ecuadorian Hermit Crab entirely outgrow their shell until they find a better offer. ¹

Conclusion 

During growth, hermit crabs need to exchange their home for bigger ones. Some species line up in a row to take the abandoned shell of the crab in front of them. It reminds me of the children´s game Musical Chairs, where the losers don´t receive a shell or a chair. Sometimes we forget that not only humans are capable of encounters as in organized assemblies. Although the crabs might not fixed the date, they know exactly which procedure to follow. Do you assume this behaviour is genetically determined? 

References:

1. Taylor, s.a. How Often do Hermit Crabs Change Shells? Hermit Crab Owner.com. Available at: https://hermitcrabowner.com/how-often-do-hermit-crabs-change-shells/ [23.10.2022].
2. Engelkind, C., 2015. Hermit Crabs Line Up By Size to Exchange Shells. Discover. Available at : https://www.discovermagazine.com/planet-earth/hermit-crabs-line-up-by-size-to-exchange-shells [23.10.2022].