Nanny Point on St. John was the place to be Thursday morning as thousands of hermit crabs made their reproductive trek to the sea.
“I’m so excited my hands are shaking,” said Caroline Rogers, a scientist at the U.S. Geological Survey on St. John.
Accompanied by naturalist Eleanor Gibney, the two waded out into the sea of hermit crabs that covered the remote beach for about 75 yards. Gibney estimated there were about 30,000 to 40,000 on the beach. And their numbers stretched way back into the vegetation that lined the rocky shore.
It was clear some were headed to the sea while others had already deposited their eggs in the area where the surf meets the rock and were on their way inland.
The hermit crabs migrated to the exact same location last year, a fact that surprised St. John resident Pam Gaffin, who first spotted them this year and last. She said scientists thought migrations switched off among watersheds, but it appears that is not the case.
Gaffin has haunted this beach and others in her efforts to spot the migrating hermit crabs. She said they began gathering in the bushes on Aug. 17, waiting for some as yet unknown signal to begin their march to the water.
She said when she got to Nanny Point shortly after 5 a.m. Thursday, only two trails of hermit crabs headed toward the water. “When daylight came, it was a river,” she said.
The migration raises many questions about hermit crab life. Gaffin said that while scientists think it’s only the females make the trek, she said she saw quite a few engaged in what looked like fighting but could have been sex.
“I saw a bubbly body fluid,” she said.
It appears the numbers were down a bit over last year, but still an impressive amount made their way down the watershed that reaches the sea at this beach on Nanny Point. Rogers said the number of hermit crabs thinned out considerably by 10:30 a.m., and Gaffin said they were all back in the bushes by 11 a.m. (A video of the scene can be viewed here.)
“Taking a nap before they go uphill,” she said.
Gibney said they prefer a rocky area so they have something to hang on to, but Gaffin suggested they prefer that area because if their eggs don’t reach the water, the tide will take them out. The eggs float in the water until they become larvae, which then find a tiny shell to call home until it’s time to shed it for the next bigger size.
Most of the hermit crabs lived in whelk shells but a good number were in star, tulip and triton shells as well as others.
Their passage was audible as their claws scrabbled over the rocks.
Like St. John’s own Paul Revere, Gaffin put the word out at around 9 a.m. to all who asked for an alert that the crabs were migrating.
St. John resident Judy Kane was on the scene.
“It is a phenomenon,” she said.
It was the tourist attraction of the day for those staying at nearby Concordia eco-resort. A steady stream of vacationers arrived to take in the sight.
“It’s amazing to see these and other creatures live their lives,” said Mindi Franks, vacationing on St. John with husband James from Stillwater, Minn.
Rebecca Holcomb of San Antonio, Texas, said watching the hermit crabs made her wish she knew more about them.
Gibney said August is a hot month for hermit crab reproduction. It appears to be tied to the phases of the moon. “It’s also when coral are spawning,” she said.
Gaffin said she recently saw a similar advance gathering of hermit crabs in the bushes at a bay near Haulover North Beach, but when she went back to check on them Thursday, the migration was apparently over because there were no hermit crabs around.
