Tag Archives: hermit crab migration

St. John’s Hermit Crab Migration

Beautiful red St. John hermit crab climbing up a rock in the beach after the mass migration to the water on August 22, 2013.
Beautiful red St. John hermit crab climbing up a rock in the beach after the mass migration to the water on August 22, 2013.

St. John had another hermit crab migration last Thursday (08/22/13) and I was able to see the very end of it. I arrived at 11:30am to the shore at Nanny Point and had to pick my way along the stone beach in order not to step on any hermit crabs.  St. John resident Pam Gaffin had been keeping an eye on the crabs for over a week as they gathered under the trees along the beach. She said she arrived around 5am and the migration was in full swing, with a pile up of hermit crabs at its deepest that would reach her elbow (if sticking her hand down into the migrating crabs.) Last year she and Steve Simonsen caught the migration on video at its height. You can watch it here.

Hermit crabs collecting along the rocky shore in St. John during their mass migration to the water to release their eggs.  Occasionally the crabs would wrestle and there is some lack of clarity on what is happening - maybe crab sex, although that should have happened earlier for egg release.  This wrestling usually brought other smaller crabs to the event who climbed on top of the two crabs...?
Hermit crabs collecting along the rocky shore in St. John during their mass migration to the water to release their eggs. Occasionally the crabs would wrestle and there is some lack of clarity on what is happening – maybe crab sex, although that should have happened earlier for egg release. This wrestling usually brought other smaller crabs to the event who climbed on top of the two crabs…?

 By the time I arrived it seems the stragglers were making their way back up to the trees, with a few hermit crabs still hoping to get close enough to the shore and incoming waves to release their eggs. Pam pointed out the area where the crabs were the thickest and the rocks were larger.  Here the hermit crabs can secure themselves in cracks and crevices in order not to get washed into the ocean with the incoming waves. Apparently the crabs fill their shells up with water in a motion that looks like they are lifting their shells up and down on their body, and this releases the eggs out in the ocean. The mass migration allows for some protection of the crabs and eggs from predators.

The view under my feet of the rocks and the way the remaining hermit crabs wedged themselves in between the rocks on the beach, hoping for a last big wave to wash over them.
The view under my feet of the rocks and the way the remaining hermit crabs wedged themselves in between the rocks on the beach, hoping for a last big wave to wash over them.
A hermit crab wedged between the rocks on the beach during the St. John hermit crab migration in August 2013.
A hermit crab wedged between the rocks on the beach during the St. John hermit crab migration in August 2013.

Despite not seeing the migration at its height, it was still more than I ever see on the beach or elsewhere at one time. They are rather fascinating to watch and with less of them converging on the beach at once their individual appearance and actions were more fun to watch! Here is a short video of a hiding hermit crab – maybe he understands english?!

My friend Gail also made it out to watch the migration and we chatted as we watched one particular crab make the long trek to the shore. She told me that she used to collect shells and leave them outside here door at her house. After a while she noticed that the nice shells she collected were gone, replaced by some ragged shells instead.  Wondering what was going on, she kept her eye on the shells.  Then one day she discovered that hermit crabs were coming up and exchanging old shells for her nice larger shells and heading back on their merry way!  After that day she made a point of collecting shells and putting them out there for the hermit crabs, a crustacean “Help-Yourself Shelf”!! I can’t tell you how badly I want to do that now! Especially since I saw hermit crabs in some shells that I did not know they live in.   (So please consider leaving any large shells you find on St. John beaches on the beach for a crab to take as his new home. But bring your camera for a good photograph instead!)

Hermit crabs collecting along the rocky shore in St. John during their mass migration to the water to release their eggs.
Hermit crabs collecting along the rocky shore in St. John during their mass migration to the water to release their eggs.
A lone hermit crab, red and purple, hiding from my camera.
A lone hermit crab, red and purple, hiding from my camera.

And St. John resident Rafe Boulon wrote a short and interesting article on hermit crabs for the St. John Historical Society. You can link to the article here.   You can watch some other video I captured: