Another interesting creature you will most likely see on St. John is a Herbit crab. These crawly little creatures live in shells that they haul around on their backs. They are also known as “soldier crabs” or “purple pinchers”.

Hermit Crab Facts

They usually live in the woods on the mountains but crawl down to the sea shore in masses where they mate and release their eggs in the ocean. While the adults are terrestrial, the larvae develop in the sea. If the eggs and larvae survive out in the ocean, tiny juveniles climb back onto land and migrate into the forests where they grow into adults. In most years, only a very small number will make it back to land. In some rare years, the numbers that arrive on the shore are mind-boggling.Observing this spectacle is truly miraculous. In 2012 St. John Photographer Steve Simonson managed to capture this on film, you can see it here.
Caribbean hermit crabs are both herbivorous and scavengers. They feed on animal and plant remains, overripe fruit, and feces of other animals.
They are usually active at night and the crabs and bury themselves beneath leaves, rocks, or sand during the day to avoid desiccation

Molting Process

Hermit have a stressful life because as they grow, hermit crabs must move into larger shells this is called molting process. This process allows for growth and limb regeneration. Young hermit crabs molt molt more frequently than adults, which may only molt 12 to 18 months. When molting, the hermit crab may burrow underground for a few days or up to eight weeks. When your hermit crab is molting, the exoskeleton will split and your crab will wiggle out of the old exoskeleton. When done, the hermit crab will eat the old shell.

Social Shell Swapping

These creatures are extremely social, foraging and traveling in groups and have formed interesting social networks. Researchers placed 20 beautifully intact shells that were a little too big for most hermit crabs at various spots around the island and watched what happened. When a lone crab encountered one of the beautiful new shells, it immediately inspected the shelter with its legs and antennae and scooted out of its current home to try on the new shelter for size. If the new shell was a good fit, the crab claimed it. Classic hermit crab behavior. But if the new shell was too big, the crab did not scuttle away disappointed—instead, it stood by its discovery for anywhere between 15 minutes and 8 hours, waiting. This was unusual. Eventually other crabs showed up, each one trying on the shell. If the shell was also too big for the newcomers, they hung around too, sometimes forming groups as large as 20. The crabs did not gather in a random arrangement, however. Rather, they clamped onto one another in a conga line stretching from the largest to smallest animal. Only one thing could break up the chain of crabs: a Goldilocks hermit crab for whom the shell introduced by Lewis and Rotjan was just right. As soon as such a crab claimed its new home, all the crabs in queue swiftly exchanged shells in sequence. The largest crab at the front of the line seized the Goldilocks crab’s abandoned shell. The second largest crab stole into the first’s old shell. And so on. Read the full article here.