social hermit crab behaviour

[colettem]

Every night at about 10pm my hermit crabs seem to accummulate on one particular rock in the middle of the tank. Usually there is about 7 of them (out of 15) that congregate there and almost look like they are sleeping. Just interested to know if anyone else has witnessed a similar phenomenon.

[Javeo]

Yep, they do tend to do this, the common brown ones show this behaviour the most.