(Photo : Wikimedia Commons)
Imagine spending the time and effort needed to remodel your home, and then getting evicted. This is what land-based hermit crabs have to go through. It seems that gangs of hermit crabs end up snatching up shells that they deem desirable from weaker comrades.
According to study from the Univerisity of California Berkeley, when three or more hermit crabs congregate, then end up reappropriating shells based on size and dominance.
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"The one that gets yanked out of its shell is often left with the smallest shell, which it can't really protect itself with," said Mark E. Laidre, who is in the Department of Integrative Biology. "Then it's liable to be eaten by anything. For hermit crabs, it's really their sociality that drives predation."
Empty snail shells are a hermit crab's home and protection. The problem is, while most of the 800 species of hermit crabs live in the ocean where empty snail shells are easy to come by, land-based hermit crabs don't have an abundant supply of homes to inhabit. The shells for land-based hermit crabs mostly come from marine snails that have been tossed ashore by the waves.
This leads land-based hermit crabs to hollow out and completely remodel their shells - sometimes even doubling their internal volume. The social gathering in order to take over a more desirable shell is an anomaly for a normally-solitary creature.
"No matter how exactly the hermit tenants modify their shelters, they exemplify an important, if obvious, evolutionary truth: living things have been altering and remodeling their surroundings throughout the history of life," wrote UC Davis evolutionary biologist Geerat J. Vermeij in a commentary in the same journal the study was published in.
Only the smallest, weakest hermit crabs can fit into un-remodeled shells, which makes a spacious, hollowed-out snail shell incredibly important for bigger hermit crabs since it is their only protection.