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30 Interesting Hermit Crab Facts

Updated: Sep 26

•Hermit Crabs Pee!

Yes! Strangely enough,they pee through their antennae glands close to the eyes. You may never actually see this happen though as it is very minimal.

•Hermit Crabs don't have ears

No, they do not have ears. They hear by sensing vibrations through their antennaes, legs and sensory hairs.

•Hermit Crabs can change their gender

Yes it is true, a Hermit Crab can change their gender during a moult. Changing from male to female and back again. It is not known how common this is or why they do it.

•Hermit Crabs don't breathe

They don't breathe air. They absorb humidity through their modified gills to "breathe" this is why they need high humidity levels.

•They have eyelashes

If you look closely at your Hermit Crabs, they have tiny little eyelashes at the top of their eyes.

•Tiny legs hold onto their shells

Hermit Crabs will use their 4th & 5th pair of legs to hold themselves into their shell. These legs are tiny compared to their other legs. They also hold onto their shell with their spiralled abdomen.

•They prefer previously worn shells

Yes, Hermit Crabs prefer second hand pants over a brand new pair. This is because the shell has been previously altered by another crab to make it a more suitable fit. The work has already been done! That shell has already been worn in.

•They mix the water in their shell to their preferred salinity

Hermit Crabs will soak in the salt water pool and fresh water pool, keeping both waters inside their shell and will mix it to their preferred salinity.

•Incredible sense of smell

They do not have a nose, but they can smell. Humidity increases their odour perception. And they can smell odours from quite far away. This may be why they all come running at dinner time. They detect smells with their antennae.

•They can grow back limbs

An injured Hermit Crab can regenerate their limbs, this includes legs, eye stalks, antennae etc. This will slowly happen over time as they continue to moult.

•Within a crew, there is a hiearchy

In every tank there is a hiearchy, and it's not always the biggest crab who rules the coup. There can be fights, antennae battles and lots of flicking to assert dominance.

•Hermit Crabs Sleep

Hermit Crabs sleep and nap during the day. You will often find them sleeping up high to protect themselves from predators.

You can tell your crabby is asleep when their legs are sticking partially out of the shell and they are partially tilted to the side, their eyes will be down and covered by the shell and they wont be moving when you go near them. Its okay, they are just napping! They usually prefer to do this in trees, second levels, in coconuts or hides.

•In the wild, they will line up to form a shell swapping conga

Probably one of the coolest things you will see wild Hermit Crabs do is when they line up in their shell size, with the largest Crab at the front and the smallest at the back. The largest Crab will take on their new shell and the crab behind them will change into the abandoned shell that the crab before them left behind, and it continues down the line until the last crab has taken a shell. This is a safe way to secure a new, preloved shell that is a size up.

•They are not actually hermits

A Hermit is someone or something who lives in solitude, or alone. Hermit Crabs are the complete opposite and prefer the company of other Hermit Crabs, living in large colonies in the wild. Referred to as "Hermit" crabs, because they live alone inside their shell.

•The oldest hermit crab in captivity

The oldest hermit crab to ever live in captivity was known as Johnathon Livingston. He lived in Florida with his owner and lived to be 44 years old before passing away in 2021.

•Hermit Crabs Poop!

And they Poop alot! They will pass their stools through their anus, into their shell in which they will then push it out of their shell during cleaning. You will often find they have discarded their poo into the pools, the food or supplement dish or into the shell shop. For some reason those are great toilet places!

•They have different preferences to foods

Not every Hermit Crab has the same taste palette, just like humans. Each Hermit Crab prefers certain flavours and will only eat what their body needs and leave the rest. Some crabs love their Veggies, and some hate them. That's why it is important to offer a large variety so even the pickiest of eaters are still finding foods to consume and each crab can consume what they actually need.

•Hermit Crabs talk

They speak in their own crabby language. Known as "Chirping" you may hear a chirping sound coming from your tank. This usually happens when an argument breaks out between Crabs or if someone is annoyed with someone else. It can also happen during shell jackings or episodes of agreesion. Usually a good sign to check on the crew in the tank to see what is going on.

•They have personalities

You may have noticed that some of your crabs are more outgoing and will happily go about their day while you stand at the tank, where as others scuttle off frightened. Each crab has their own personality and if you get to know your crabs, you will see it too. Some are outgoing, shy, agreesive, active etc

•They have 10 legs

Thats right, 10 legs! 3 pairs are outside of the shell, while the other 2 pairs are within the shell. The 4th and 5th set of legs are much smaller and are used for grooming, removing poo, and hanging onto their shell.

•All Captive Hermit Crabs are wild

There is one exception to this, any Hermit Crabs in Australia that have been captive bred are not from the wild. Currently there are only a small amount. The rest of the Captive Hermit Crabs in Australia (including your own) have all been taken from the wild.

•They clean themselves

You may catch a glimpse of your crabs cleaning themselves. They will often use their 4th pair of legs for cleaning their gills, shells, etc. It is a very interesting thing to observe.

•Altering their shells

Hermit Crabs will take a shell that they like and start to alter it while wearing it to make it fit better. They do this by chipping pieces away using their large claws, and then consuming it. This is a great source of Calcium. It is also why painted shells are not ideal, incase your crab consumes the paint.

•They would rather be torn apart than give up their shell

During an attempted shell jacking, or if you try to pull a crab from their shell. They will hold on for dear life. Often letting themselves be torn apart, rather than let their shell go. This is why you should never try to force a crab from its shell and should always intervene if there is a shell jacking attempt.

•The female picks the male for mating

When mating, most males will show interest in a sexually matured female during breeding season. However, it is entirely upto the female to decide who she will mate with.

•They can eat their tank mates

Hermit Crabs NEED protein in their diet. Atleast 50% of their diet should be made up of protein. When this is not available, some hermit crabs will go to great lengths to find that protein, and that includes consuming their tank mates.

If a hermit crab comes across a moulting crab, they will often consume the moulting crab as a source of protein.

•Megalopae eat eachother

Once Zoea transform into their Megalopae stage, they become extremely carnivorous. They will begin to eat eachother.

•Eating their own shed exoskeleton

Eating their exoskeleton is not only normal, but encouraged. It is a great source of Calcium.

•Over 800 Hermit crab species

There are over 800 Hermit Crab species worldwide in the wild, however, majority of these are sea dwellers.

•There are 17 Coenobita species kept as pets

Only 17 Hermit Crab species are commonly kept as pets across the world.

• Wolfie sleeping on top of the hanging coconut

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