Resource availability: Ancient homes for hard-up hermit crabs.

Mollusc shells are a vital but sometimes scarce resource for hermit crabs, protecting them from mechanical damage and desiccation, but they require continual replacement as the crab grows. I have discovered that Coenobita rugosus, a large, tropical, semi-terrestrial hermit crab, will resort to using fossil shells when no other suitable casing is available. These unlikely mobile homes fall out of coastal limestone as it is eroded by the sea in southwestern Madagascar, placing the occupants alongside Homo sapiens as resourceful exploiters of prehistoric animal remains.