Hermit crabs are becoming increasingly popular as pets, but their behavior can confuse owners. That is why it is so important to understand why hermit crabs act the way they do.
Hermit crabs love to climb and dig for fun. They also burrow under their substrate to destress, regulate temperature, and molt. They like to stay clean, so bathing water is a must. Hermit crabs are usually docile, but may fight with each other or pinch owners. This is usually preceded by chirping, which is a warning sign of overstimulation.
Hermit crabs have complex needs but are low maintenance once these requirements are met. If you take the time to understand hermit crab behavior, you can create a welcoming habitat.
Hermit Crab Social Behaviors
Hermit crab behavior in the wild can differ from hermit crab behavior in captivity. They know how to survive in the wild, but have a tough start to life. If a hermit crab survives to adulthood, it is driven by survival instincts.
In captivity, things can change. This is often an anxious and stressful experience, especially initially. Suddenly, hermit crabs are exposed to humans and all our foibles. What’s more, it’s tough for the hermit crabs to hide and avoid us in a restricted space.
As a rule, hermit crabs will adapt to life in captivity, especially if paired with friends. These are social animals that dislike living alone. Every hermit crab has a unique personality, but they do have core behaviors.
Digging is arguably the most common behavior of any hermit crab. These animals dig for recreation, using pincers to get substrate out of the way. Hermit crabs often burrow under obstacles rather than walking around, or climbing over, them.
Hermit crabs like to dig in damp conditions. Consider adding a little moisture to the substrate of your tank. If the substrate is too dry, hermit crabs will tip over baths and drinking water.
Always ensure that your hermit crabs have enough substrate to dig into. 3-4 inches of substrate is the bare minimum. Most hermit crab habitats will need at least 6 inches of substrate, such as sand.
Burrowing Under Substrate
Burying themselves underneath the substrate of an aquarium is especially common when hermit crabs first enter captivity. Hermit crabs bury themselves for a range of reasons. These include:
- Regulating body temperature (cooling off if too hot, warming if too cold)
Whatever the explanation for a hermit crab burrowing, the animal must never be disturbed. Hermit crabs burrow for many reasons. Every one of them is essentially code for, “leave me alone”, though.
If you plan to care for hermit crabs, understanding the molting process of hermit crabs is essential. Hermit crabs don’t grow a shell. They periodically outgrow their exoskeleton, shedding this and growing a new, tougher one. This can take weeks or even months.
Hermit crabs display signs that they are preparing to molt, which we will discuss in a moment. What matters most is that you leave a hermit crab well alone while it molts. Patience is a virtue that hermit crab owners require in abundance.
As molting hermit crabs remain underground and appear motionless, some owners fear their hermit crabs are dead. This is possible but unlikely. Never shake the shell of a molting hermit crab to see if it falls out.
Behavior Before Molting
The molting schedule of hermit crabs depends on sex and age. Young males molt most frequently. Once hermit crabs reach adulthood, they start to molt less often. Signs that your hermit crabs are preparing to molt include:
- Eating more than usual to store fat
- Drinking and bathing more to store water in the shell
- Coloration fading to a dull gray
- Growing lazy and lethargic, less inclined to climb or burrow
- Digging in numerous locations, testing the substrate for the best burrowing spot
If you see a molt impending, move your hermit crabs to a private habitat. As molting hermit crabs shed their exoskeleton, they are vulnerable throughout the process. Hermit crabs are more comfortable alone until they have grown a new exoskeleton.
Behavior During Molting
A hermit crab’s behavior during a molt will be invisible to you. Hermit crabs remain underground throughout the process. As discussed, this is where they need to stay. Do not dig up your hermit crab, even to check if it is still alive. The process takes as long as it takes.
Do not worry about sustenance. Molting hermit crabs keep themselves alive throughout the process. Typically, molting hermit crabs drink water stored in a shell and eat their shed exoskeleton. This is packed with essential calcium, much like cuttlebones.
Once hermit crabs conclude a molt, they emerge from under the substrate. Once more for good measure, you should wait for hermit crabs to do this of their own accord. They will resurface on their schedule.
Behavior After Molting
Hermit crab behavior immediately post-molt can vary. It depends on the personality of your hermit crab. Some will be cautious until they are certain their new exoskeleton has hardened up. Others will be emboldened by an increase in size and mass and become more confident.
Most hermit crabs will be hungry after molting, though. Do not be alarmed if your hermit crabs eat more than usual. Allow a little flexibility in food and treat portions.
More importantly, hermit crabs will immediately seek a new shell after molting. The previous shell often cracks and breaks during the molting process. Provide a plethora of options to prevent conflict with other hermit crabs.
Hermit crabs are not the first animal people think of when considering clean pets. Hermit crabs are surprisingly fastidious, though. They loathe living in unsanitary conditions and clean up after themselves.
Hermit crabs have unique bathroom habits. Hermit crabs appear to urinate from their antennae, but this isn’t the case. A hermit crab will emerge from its shell to pee. Hermit crabs poop inside their shells. They will flick this waste out of the shell onto the substrate. Their feces is often eaten.
Hermit crabs regularly bathe themselves. Provide bodies of saltwater and freshwater to provide a choice. The hermit crab will submerge in this water. This will clean the crab’s body and potentially kill any mite infestations.
Ensure these baths are not too deep. Terrestrial hermit crabs have small lungs and cannot breathe underwater indefinitely. If the water is too deep for a hermit crab to escape, it will drown.
Never use tap water for a hermit crab’s bath. This contains copper and chlorine, both of which are fatal to hermit crabs. Use filtered water, or better yet, bottled water. This also means that you should avoid manually bathing a hermit crab unless strictly necessary.
Cleaning a Hermit Crab Tank
Spot cleaning is similar to clearing a cat’s litter tray. Scoop the surface of the substrate in your tank. This will remove uneaten food and fecal matter. Consider wiping down any walls, too. This will prevent mold or algae from taking hold.
A deep clean of a hermit crab enclosure is a longer process. It is also disruptive for your hermit crabs, so don’t do it too often. Once every 3 months is usually fine. Relocate your hermit crabs and completely clean the tank, replacing the substrate and washing accessories.
In the wild, hermit crabs are natural climbers. This activity services many purposes. Primarily, it’s simply recreational. Hermit crabs also climb trees or algae to scavenge for food or hide from predators or rival hermit crabs.
As per the Journal of Crustacean Biology, female hermit crabs climb trees ahead of releasing their eggs into the sea. This ensures the crab has a clear aim at a low tide. It also gives the larvae a fighting chance of survival.
To keep your hermit crabs happy in captivity, you should allow them to climb. You will likely notice that your hermit crabs take this opportunity at every opportunity,
For your hermit crabs to safely climb, they’ll need appropriate apparatus in their habitat. This will provide the opportunity for recreation and exercise in a tank. This, in turn, keeps captive hermit crabs happy. Common climbing apparatus that can be applied to a hermit crab enclosure include:
- Thick rope
- Netting along the walls of the tank
- Rocks and logs
- Plastic building blocks, like Lego or Duplo
- Solid plastic plants
- Burlap sacks
- Corkboards against an aquarium wall
If you provide these surfaces, your hermit crabs will be perfectly content to explore their surroundings. The more climbing opportunities you provide, the more you’ll mimic the natural habitat of hermit crabs.
Hanging from Roofs
Hermit crab climbing will not begin and end with scaling surfaces. Many hermit crabs will also hang from the ceiling of an aquarium, like bats.
In some cases, the hermit crabs are sleeping in this position. Climbing is exhausting for hermit crabs. Once the animals have scaled to a height they desire, they’ll take a nap.
This position is also safer for hermit crabs with coveted shells. Sleeping on a surface level may attract attention from rival crabs. These competitors will instigate conflict for a shell. We’ll discuss that in more detail later. This aggression is unlikely while elevated.
Do watch your hermit crabs while they hang. If the hermit crabs are pushing with their legs, they are trying to escape. The legs of hermit crabs can be powerful, especially when several of these animals team-up. Weigh down the lid of your aquarium to be on the safe side.
Protection from Falls
One potential side effect of hermit crabs climbing is falling. These falls can be dangerous for your crabs. The shell may be cracked or broken upon impact. Alternatively, hermit crabs may land on their back and be unable to right themselves. This will cause stress.
Protect hermit crabs from the impact of falls by providing sufficient levels of substrate. If your hermit crabs are natural climbers, increase the minimum amount to around six inches. This will create enough padding to ensure a soft landing in the event of a tumble.
More importantly, try to prevent falls from occurring in the first place. Provide plenty of opportunities for your hermit crabs to grip while climbing. Netting is recommended for this purpose. The more hermit crabs have to hold onto, the less likely they are to lose balance.
Wild hermit crabs are omnivorous scavengers. This makes them largely unfussy about what they eat. Hermit crabs sustain themselves on what they find. This could include algae, leftover food scraps, corpses of other animals, and even fecal matter.
This scavenging instinct also means that hermit crabs like variety in their diet. As per Marine Ecology, hermit crabs rarely eat the same thing twice in 24 hours. To keep your hermit crabs interested in food, change their diet daily. Popular foods for captive hermit crabs include:
- Fresh fruit and vegetables
- Hermit-crab specific food pellets
You’ll be able to tell if your hermit crabs are enjoying a meal. Hermit crabs eat interesting food quickly. If hermit crabs are less engaged, they will merely graze. You’ll likely find that one hermit crab eating attracts others.
Hermit crabs should be fed daily. These crustaceans have small stomachs and appetites to match, though. You may find traces of uneaten food in the tank. Remove this before it rots and creates a bacterial hazard.
The best time to feed hermit crabs is early evening. Hermit crabs are nocturnal and will wake up hungry. They can also smell food from as far as six feet away.
Place food in a dish just around the time that your hermit crabs typically wake up and become active. They will likely feed and go about their business.
Hermit crabs are widely considered to be calm, friendly, and docile pets. Just like any animal though, hermit crabs act on instinct. This can lead to aggressive behaviors if hermit crabs feel threatened.
What’s more, every hermit crab has its own personality. This means that some crabs are more belligerent than others by nature. You will get an idea of a hermit crab’s persona by watching it interact with others.
Some level of aggression, whether unprovoked or in self-defense, should always be expected from hermit crabs. Thankfully, these episodes tend to be few and far between.
Aggression Toward Other Hermit Crabs
While hermit crabs are social and love to live in groups, they will fight on occasion. These conflicts vary in severity, depending on the circumstances.
Hermit crabs often engage in ‘antennae wrestling.’ This is primarily a game for recreation, though it also establishes a hierarchy of dominance. Like all animals that live in colonies, hermit crabs like to establish a pecking order.
Hermit crabs will also fight over shells. Shells are all-important to these animals, as they offer protection. If a dominant hermit crab feels that a subordinate has a superior shell, it will instigate a conflict for it.
This is known as ‘shell rapping’. The dominant hermit crab knocks against the shell of the other. If the subordinate hermit crab accepts the challenge, it will emerge.
These hermit crabs will then fight, though they rarely do so with the intent of wounding. As per Proceedings of the Royal Society of London, winners and losers are decided by energy levels. Eventually, one hermit crab will cede and admit defeat.
If the aggressor wins the battle, it will claim the shell vacated by the loser. The evicted hermit crab will then typically claim the shell left by its conqueror. Other hermit crabs may then try their luck though, leading to a cycle of conflict until all crabs are satisfied.
Aggression Toward Other Animals
Some hermit crab owners keep these animals with other pets. This is common in aquatic tanks. Fish and turtles are common tankmates for hermit crabs.
In such instances, hermit crabs will rarely attack other animals. The opposite is likelier. Hermit crabs are at the bottom of the wild food chain. Fish and sea turtles often feed on them in the ocean.
If your hermit crab escapes its enclosure, it will be wary of other household pets. A hermit crab will flee and hide from a cat or dog, not attack. Again, though, the same cannot be said in reverse. Keep your hermit crabs safely enclosed for their protection.
Aggression Toward Owners
Hermit crabs are cautious by nature. They, quite understandable, will initially fear humans. Get your hermit crabs used to being handled as early as possible. It will be necessary when you need to relocate them for tank cleaning. To handle a hermit crab safely:
- Gently lift the hermit crab by the shell with your dominant hand. Never grab a hermit crab by the legs
- Stretch the palm of your other hand, leaving no loose skin to pinch
- Place the hermit crab in the palm of your hand
- Let the crab walk and crawl over you to build trust
This may still result in pinches, but they will not hurt too much. Also, be aware that not all pinches are based on aggression. The hermit crab may just be using your skin as leverage to climb and maneuver.
Hermit crabs are not as vocal as more common domestic animals, like dogs or cats. They do make noise, though. Hermit crabs communicate and verbalize through a process called stridulation. This sounds like a cross between a croaking frog and chirping cricket.
Hermit crabs do not verbalize through their mouths. Instead, it is believed that the sound is created by rubbing body parts together. You will often hear stridulation when handling a hermit crab, or if two hermit crabs come into conflict.
This suggests that stridulation is inspired by stimulation. In turn, it could be considered a fear-based response. Scientific research has never fully confirmed why hermit crabs vocalize.
By learning what hermit crab behavior means, you can create a better life in captivity. Contented hermit crabs will eat, groom, and exercise. If this describes your hermit crabs, you’re doing a great job of caring for them.