Hermit crabs are the clowns of the crustacean world; they have a swagger and character that justifies their popularity as marine aquarium pets. I think that hermits also started me on my career path as a marine scientist. When I was a young girl growing up in the 1950's, my mother, who was a teacher and loved reading, and I would haunt the Daytona Beach public library. Every week we would bring back a tall stack of books, and check out another stack. One children's book that I always looked for was 'Pagoo' written by Holling Clancy Holling and beautifully illustrated by his wife Lucille Webster Holling (photo of book cover above). The hero of the book, Pagoo (short for Pagurus, a common hermit crab genus), relied on the urgings of 'Instinct' as he grew from a tiny larva drifting in the plankton, to a newly molted hermit looking for his first shelter in a tidal pool, to a big crab fighting other hermits for prime snail shells. The story introduced many other fascinating marine creatures living in the rocky intertidal zone of New England coasts. I was hooked!
Hermits, cousins of true crabs, have soft vulnerable abdomens that they protect from predators by occupying empty shells. As the crabs grow larger, they have to find successively bigger shells to protect their tender nether parts. Sometimes suitable shells are in short supply. The shells cannot have holes drilled into them by moon snails, for instance, or the hermit's abdomen could be subject to the sharp poke of another hermit crab's claw through the hole. If an empty shell is not available, a needy crab will attempt to evict another hermit from its shell. Usually this tactic is unsuccessful, but the sparring matches that ensue are fun to watch.
The largest hermit crab found on the Georgia coast is the thinstripe hermit, Clibanarius vittatus. This monster grows large enough to drag around knobbed whelk shells. I found three of these hermits in a crab trap once, attracted by the rotten fish heads in the bait well; all were in hefty whelk shells.
A thinstripe hermit crab in a knobbed whelk shell; a moon snail shell with a hole rasped out by another moon snail lies in front of the crab. Photo courtesy of Jo Okeefe, used with permission.
Other species of hermit crabs along the Georgia coast are much smaller, with plain white claws. The most numerous are the dwarf, or common, hermit crab, Pagurus longicarpus, and the flat-clawed hermit crab, Pagurus pollicaris. Look for aggregations of these amusing little crabs in beach sloughs as they scavenge for tidbits or dead animals washed up by the waves. These hermits, like Pagoo in Holling's book, sport a wide variety of shells, from tiny spiral auger shells on very young crabs to two-inch-wide moon snail shells inhabited by the largest adult hermits.
Images of hermits and other crabs common on the U.S. Atlantic coast are posted on the Okeefes' website: