Sequential shell swaps in hermit crabs

January 23, 2020 • 2:30 pm

Here’s another Attenborough video featuring the lifelong attempts of hermit crabs to find shells that fit them as they grow. A hermit crab without a shell is a pathetic thing (see several at 2:39), easily taken by predators or cooked by the sun. Here’s a stunning behavior in which a line of crabs forms in order of size, with the aim of each one swapping up to a bigger shell within a matter of minutes. Or course, the biggest crab needs an empty bigger shell to move into, which apparently is the case here. The picture of the lineup at 1:32 is fantastic.

The video comes from “Life Story,” part of the great BBC Earth series.

12 thoughts on “Sequential shell swaps in hermit crabs

  1. The music is dippy, but those crabs are adorable! I had no idea that they exhibit this behavior — I would have thought there were plenty of shells of all sizes available.

    1. Why go to the expense of growing your own shell when there are perfectly good shells littering the sea floor? Put your resources into reproduction. Just a guess.

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