Strange Happenings: Bubbles on a Hermit Crab in a Shell

Bubbling seashell with hermit crab inside.

It was Fall in Florida and we were boating. When I was walking around a muddy island at low tide I came across this strange sight. A mound of bubbles in the sand.

The snail was not in the pear whelk shell, it was a hermit crab inside. I began to see his legs poking out through the foam. I have tried to research this phenomenon and have had no luck.

This is the first and only time I’ve seen something like this. No other shells / hermit crabs on the island were doing this. If you know, I’d love to hear.

More travels around the Indian River

Fiddler Crabs Along The River

Fiddler crabs are very tiny and they are a favorite food of Sheephead fish. We see Fiddler crabs in groups on the sandy shores of little uninhabited islands along the saltwater river. They scurry around in groups, or pop into their little holes when they see us.

Thousands of crabs hurry up into the mangroves to hide as we approach. They are very tiny and difficult to photograph. I do however have a pretty cool video – below.

Fiddler crabs

During Sheepshead fishing season, local bait shops sell fiddler crabs to fishermen. Unfortunately, Sheepshead fishing is very popular because it’s good eating fish, and the crabs are often sold out. You can catch your own Fiddlers, but we never have. But we do sometimes specifically look for sheepshead. They are often found around docks and piers where they eat barnacles clinging to the pylons.

All three photos below show Fiddler crabs but they are so tiny it’s hard to make them out.

Low tide is a good time to see Fiddler crabs scurrying around the grasses and mangroves. They need the water to survive, but can’t live submerged. They scurry into little holes in the sand and hide there when the water comes up as explained at the Florida Fish and Wildlife page.

Grass and sand where fiddler crabs live
This is home to fiddler crabs

My phone doesn’t take great zoom photos, but I had to get this crab photo without scaring him into his hole. The male crabs have one large claw so I would say this is a male and these crabs are very tiny. Little piles of sand pellets are left all around the holes they make.

The Fiddler crab doesn’t have a long life span, but is an important food source for more than just crustacean loving fish.

Fiddler crab
Fiddler crab

For some reason my “Florida’s Living Beaches” (affiliate link to Amazon) reference book does not mention this type of crab. I have the first edition of this book, so they may be mentioned in the second edition. I am surprised at this omission because they are an important part of the coastal ecosystem.

My information on this page came from reliable online sources mentioned in this article. All photos are my own.

Do Marine Hermit Crabs Kill Snails For Their Shells?

A hermit crab inside a crown conch shell while the snail is still inside makes me question what is going on here?

From everything I’ve read about hermit crabs, the consensus is that they don’t harm snails. They wait to find an empty shell and then move in.

When beach-combing, I see far more hermit crabs inside shells than actual live conchs and whelks, or the snails which made the shell. I find that odd, since there is quite a good ecosystem out on the mud flats. Very few people mess with beach nature out there. Visitors prefer the ocean beaches, and even the boaters either fish or sit and enjoy the tranquility found on a little sandy beach away from crowds.

It’s curious that I don’t see many more living snails. Then, I came upon this unusual scene.

Hermit Crabs and the Crown Conch

We pulled up to a little island the other day and as soon as I stepped out of the boat I saw this cluster of hermit crabs. A cluster of hermits in various shells is a regular sight, but one of the shells had a conch inside. And when I looked closer, I saw something I’d never seen before.

gathering of hermit crabs
Many hermit crabs surround a crown conch snail

One hermit was already inside the conch shell. The other hermit was on top of the shell and looking for access. Watch my short video of these hermits with the conch snail, which is not the greatest, but shows what is happening in the picture above.

A hermit crab had crawled down inside the shell – even though the conch was still inside! I don’t know if the conch was alive but the shell was not vacant. It appeared to me that the hermit crab was shoving the snail out of it’s home.

If this is the case, then did the hermit crab kill the conch? It would also explain the abundance of hermit crabs in the area. After all, if they have to sit around and wait for an empty shell, it could be a long wait. Why not just oust the snail and grab the shell?

hermit inside a live conch
Both the conch and hermit crab inside the shell!

I took a bunch of photos and have chosen the best to share here. You can see the legs of the striped hermit crab holding on, and wrapping round, the snail. I don’t know if the snail is still alive, but the crab pushed it’s way in even though the shell was occupied by the shell-maker. Did the snail die (for some reason – and was not eaten) and the crab was disposing of the body? Or did that crab cause the snail’s death?

The crown conch snail has black splotches, which can be seen in these pictures, although the foot seems shriveled (see my photo below of a live crown conch snail). The hermit crab was tucked way down behind the conch. I touched it’s legs and it didn’t care. He held on tightly to the snail, which also was not moving.

The Black Speckled Foot of the Crown Conch

The foot can be seen on another crown conch that I found a while back. In the photo below the foot is emerging from the spiky shell. That conch was alive, and it leads me to believe that the one pictured above may have been dead. The foot is yellowed and shrunken. But, did the snail die on it’s own, or did the hermit crab have something to do with that?

crown conch foot
Photo of a living crown conch snail – see the black speckled foot

The Mighty Grip of the Hermit Crab

By the way, those hermit crabs have a mighty grip. Not long ago we visited this same island and I saw many big tulip shells. One shell had a hermit crab inside who was tightly holding onto a pear whelk. It seemed that the pear was empty, and the hermit had such a tight grip that I could hold these shells off the ground by pulling on the tip of the whelk. He was not going to let that shell go!

I can’t imagine why, since the hermit was already in a very nice shell. Do they covet every empty shell they see? There may have been another hermit crab inside the pear whelk, but I didn’t see one. Almost all hermit crabs I see are the striped variety.

hermit inside tulip holding pear

So my question is, do hermit crabs kill marine snails just to take over their shells? I’m not sure why a snail would simply die. Aren’t they usually eaten by birds or other snails? Of course, I don’t know and maybe snails do die of other causes.

Then again, if hermit crabs are killers, it would explain the huge number of them living inside seashells in this area. More observation and investigation, on my part, is needed. One thing is for sure. Both the hermit crab and snail were in the shell at the same time.

Answering the Question – Maybe

The book Spirals in Time, The Secret Life and Curious Afterlife of Seashells (this is an Amazon affiliate link) has some information about hermit crabs. On page 138, the author Helen Scales writes, “The one thing that hermit crabs never do is kill the occupant of a shell before moving in.” She is a marine biologist based in England.

I believe in scientific studies, but isn’t it possible that a few hermit crabs may have gone rogue and become impatient with waiting for snails to die? They have claws. And some of the hermit crabs I’ve seen are pretty large.

With a large population of hermit crabs in the area, finding empty shells to inhabit must be tough. Maybe the hermit crabs in this area are desperate enough to become resourceful in new ways. They will die without a shell to live in.

In closing, never buy hermit crabs as pets, or pick one up from the beach to take home. Being in captivity shortens their life, by a lot. And their existence is miserable compared to being in the wild. Read more about why it’s a bad idea here.

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