Your hermit crab tank contains a few inhabitants that bring some excitement and joy to your days. Just looking at their relatively big eyes and the intelligence that you often see in them can sometimes make you wonder about their sight.
Do hermit crabs see their surroundings as well as we do? Do they have sharp eyes or just enough sight to get by without bumping into something?
In this article, we’ll answer all the questions you might have about hermit crab vision to please that curious inner voice of yours. So, let’s dive in!
Even though there isn’t a sufficient number of studies yet to let us know exactly how well hermit crabs see, several ones managed to give us a peek into hermit crab vision.
After taking a look at these findings, we finally have our answer, and we’ll offer it to you without all the confusing scientific jargon!
Simply put, hermit crabs have average eyesight, and its main purpose is to detect threats instead of making up fine, intricate details in their surroundings. Think of it as an alert system that focuses on the big picture, leaving all the tiny pieces of information to the other senses.
The irony is that while hermit crabs have eyestalks that are capable of rotating 360 degrees, their vision remains limited compared to many animals and humans.
Hermit crabs can surely recognize different shades and colors, but defining shapes with their sight isn’t their strongest asset.
This is why hermit crabs rely on their sense of smell, taste, hearing, and touch to become more familiar with their environment.
Let’s take an even closer look at the anatomy of a hermit crab’s eyes, shall we?
Crustaceans, and hermit crabs in specific, have compound eyes. In other words, the eyes are divided into thousands of smaller orbs, and these are called ommatidia.
Because each one of those orbs comes with its own cornea, lenses, and photoreceptor cells, they all allow the crabs to catch sudden movement to stay away from danger.
Despite having hundreds of eyes, it doesn’t mean that a hermit crab’s sight is better than a human’s. It simply translates to having the ability to be more aware of the contrast between light and dark, which aids in a crab’s survival.
This is why it’s easy for a hermit crab to get startled by someone opening the door or entering the room, even if it’s not a sudden movement.
Because of the unique structure of a hermit crab’s eyes, scholars believe these crustaceans can’t identify the outline of shapes or tiny details. For example, if you place a scarf that’s mostly red with a white pattern in front of your crab, it’ll likely see the piece of clothing completely red.
Yes. The inner workings of a crab’s eyes are similar to those of most insects because they’re all compound eyes.
Remember how you’ll often see a fly hit a wire mesh screen over and over to get inside or outside, simply believing it to be a window? That’s because the eyes of flies don’t process the shape of the grid, but they see the scene behind it.
That’s probably how things are with crabs, although we’re still waiting for more studies to confirm this.
Yes, hermit crabs have exceptional night vision, which only makes sense because they’re nocturnal creatures. Again, their enhanced nighttime sight is due to how their eyes are built.
In a dimly-lit room, the light rays will pass into each ommatidium in a crab’s eyes. What happens afterward is that the light will go through each tiny lens, where it gets absorbed and then bounced around the eye.
Because of this mechanism, it’s no wonder that a hermit crab’s eyes are sensitive to light. In dim conditions, that’s a plus, but this hypersensitivity is a downside if the crab’s eyes are exposed to bright light.
Still, despite their superior night vision, hermit crabs rarely depend on it to explore their surroundings. They’ll identify any nearby object using their antennae and sense of scent.
Of course, no one is 100% sure about the distance that a hermit crab can see. Still, based on how their vision works, it’s safe to assume that hermit crabs can see far objects better than those that are immediately in front of them.
During those few moments that hermit crabs note the shape of something moving toward them from afar, they need to make a quick decision.
If it looks like a threat, they’ll hide.
On the other hand, more familiar shapes like those of their hermit crab tank mates or their human owners won’t trigger this reaction. Hermit crabs will be more welcoming toward them.
As we’ve already pointed out, hermit crabs can tell different color shades apart. This shows in their tendency to pick showy, brightly-colored shells in the wild, which is enough proof of their color recognition.
Wild hermit crabs will go for shells that contrast with their native substrate.
After performing several studies on hermit crabs, scientists have found that these crustaceans mostly react to the colors red, green, and blue. However, blue usually triggered a flight reaction and caused the crabs to hide.
Therefore, if you’re ready to place decorative items in your hermit crabs’ tank, make sure to go for things that come in shades of red or green. Black, gray, white, and brown should be fine, too.
Unfortunately, hermit crabs aren’t likely to recognize their owners with their vision because it doesn’t help them make up the details of your face. So, your hermit crab will surely notice when you’ve entered the room and stepped closer to the tank, but your physical features will look blurred.
Don’t feel disappointed though, because hermit crabs bond with their pet parents using other senses. Mostly, it’s the hearing sense that lets them recognize their owners.
Thus, while your crab won’t clearly see your face, it’ll most definitely become familiar with how your voice sounds. This is why it’ll come skittering to welcome you after hearing you talking to it.
We know that beginner hermit crab keepers might think that their little buddies are blind because of the way that they sometimes behave.
See, hermit crabs are prone to bumping into solid objects in their tanks and even their tank mates. However, this doesn’t mean that they’re going blind; it’s just that they like to explore their surroundings using their antennae.
A hermit crab will come into close contact with an object to test its steadiness. If it’s solid enough, this means that it’s safe to climb on top of it without worrying about falling over.
Also, hermit crabs push against each other during playtime. In other times, it might signify that they’re testing their strength to determine an order of dominance.
Unless they’re being vocal about their harmless fighting, in which case it won’t be harmless, you shouldn’t be concerned about them getting in trouble!
The anatomy of hermit crab eyes is so unique that you just can’t ignore how they function.
After some digging, we discovered some curious facts about the eyes of hermit crabs that we must share with you so that you can appreciate their awesomeness!
- Hermit crabs don’t shed their eyestalks if they’re stressed (it can happen with other limbs)
- Hermit crabs might severe their eyestalks if they become exposed to harsh lighting because of their eye sensitivity
- Hermit crabs that lose an eyestalk may grow it back, but it won’t contain a working eye
- Hermit crabs can sometimes have glazed eyes, and it usually means they’re ready for molting
- During the molting process, a hermit crab’s eyes will have renewed lenses, and this often clears the glazed look in its eyes
- Hermit crabs don’t have eyelids, so they can’t close their eyes
- Instead, the eyes of these crabs come with a membranous protective layer to keep irritants at bay
Seeing your hermit crab bumping into the rocks in its enclosure over and over might make you wonder about its ability to see. Yet, now that you’ve read our article, you know that your little buddy isn’t blind!
Hermit crabs have an average vision that allows them to see the big picture without making up the small details. So, they can rely on their sight to detect potential threats but not to recognize objects or creatures in their surroundings.
We hope that, by learning more about how your hermit crab vision works, you’ll understand its behavior a bit better. That’s a cool way to bond with your tiny friend!
I have a bachelor’s degree in Film/Video/Media Studies, as well as an associates degree in Communications. I began producing videos and musical recordings nearly 15 years ago. I am a guitarist and bassist in Southwest MI and have been in a few different bands since 2009, and in 2012 I began building custom guitars and basses in my home workshop as well. When I’m home, I love spending time with my three pets (a dog, cat, and snake) and gardening in my backyard. I also like photographing wild birds, especially birds of prey.