Hermit Crab Behavior in Captivity | Food, Climbing, Digging & Aggression

Hermit Crab Behavior in Captivity | Food, Climbing, Digging & Aggression

Hermit crab owners around the world love to watch their crabs. Despite the fact that they are rather primitive creatures, hermit crabs engage in a number of fascinating behaviors. If you spend time watching your hermit crabs, you’ll come to know each individual crab well and will recognize typical hermit crab behaviors.

You know by now that hermit crabs do best when they share their homes with other hermit crabs. That’s because these interesting creatures are highly social with one another. In the wild, hermit crabs live in large groups and interact with one another regularly. In captivity, hermit crabs do the same.

They rub antennae with other crabs, crawl all over each other, and basically act like they all are part of one big group – which they are. If you take the time to observe your crabs in the evening hours, you’ll see them interacting as only hermit crabs can.

You’ll watch them do things such as gang up to knock over items in their crabitat by piling on top of each other, gather together in the food dish to share a treat you may have given them, and simply greet one another with antennae waving.

What does hermit crab eat in captivity?

Watching your hermit crabs eat is one of the most enjoyable aspects of owning these special crustaceans. Hermit crabs have a fascinating way of partaking in meals.

They are good at knowing what kind of food you have placed in their crabitats, since they have the ability to see and smell food from as far as 6 feet away. If you put something that is particularly fragrant in their food dish after sunset, you’ll no doubt see your crabs come forward to investigate.

Hermit crabs also respond to the sight of other hermit crabs eating, so you are likely to see more than one crab feasting at a time. When hermit crabs eat, they pick the food up with their claws and put it to their mouths. You can enjoy watching your hermit crab “shovel” his food into his mouth. Favorite foods go down the hatch faster than more boring (by crab standards) items.

Self Grooming

Although they might not be as fastidious as cats, hermit crabs do like to keep themselves clean. Self-grooming is one of the many interesting behaviors you will see in your hermit crabs.

Crabs with clean body parts are able to see and function better in their environment. Keeping the inside of the shell clean is also useful for hermit crabs since it prevents sand and other irritants from building up inside where these particles can irritate the crab’s tender abdomen.

For these reasons, crabs focus on keeping their claws, legs, eyestalks, antennae, and interior shells clean. They groom their claws by picking dirt and sand out of the crevices with their opposing claw. Crabs clean their legs by rubbing them on each other.

Their eyestalks and antennae are rubbed clean using their legs. Cleaning the interior of the shell requires a different approach. The crab uses his back legs to scrape the inside of the shell, pushing out any debris that may be lodged inside. The opening of the shell is kept clean using the small claw. You may not know your crab is cleaning the inside of his shell because you won’t be able to see what is going on, but if he appears to be doing something inside there, he is most likely cleaning house.

Climbing

Hermit crabs love to climb. In the wild, many hermit crabs use this skill to climb trees looking for food. In captivity, hermit crabs show their love of climbing by scaling anything they can get their claws on. If you have provided some climbing areas for your hermit crabs in their crabitat, you’ll see them showing off their skills regularly.

Climbing mats, textured ornaments, and even screen tops are all suitable climbing surfaces for hermit crabs. In fact, hermit crabs are such good climbers that it’s important to keep the top of your tank securely fastened.

Otherwise, your crabs may climb right out of their crabitat! Crabs are able to climb by hooking the tips of their legs onto small protrusions on a vertical surface. They hoist themselves up, shell and all, and climb using these natural rungs in whatever they are climbing.

Hermit crabs have also been known to climb to the screen tops of aquariums, positioning themselves upside down and holding on. Climbing is a strenuous activity for a hermit crab. You may see your pet take a snooze on a vertical surface, once he has climbed as high as he wants to.

Digging

Digging is another important crab behavior. Hermit crabs dig to get past an object that’s in their way (often instead of simply going around it), to bury their bodies to cool themselves off when they are feeling warm, and to hide. When hermit crabs dig, they use their pinchers to move substrate out of the way.

They prefer to dig in moist areas, which is why owners often find their crabs’ water dishes knocked over in the mornings when they come to check on their pets. If the substrate around the water dish is damp, the crabs will dig into it.

Likewise, if the water dish crosses their path and the substrate is damp around it, they will dig underneath, upsetting the dish. Some hermit crab owners report that their crabs deliberately dampen areas of the substrate by filling their shells with water from the dish and then crawling to another area, where they let the water dribble out. The crabs then dig in the damp substrate.

Because hermit crabs enjoy digging so much, it’s important to provide them with substrate they can easily move with their tiny pinchers. For optimal digging conditions, I recommend at least 4 to 5 inches of substrate for smaller crabs. If you’re housing larger crabs, the substrate should be 7 to 10 inches deep.

Aggression

While most hermit crab behaviors are endearing, one common behavior is not. Crab-on-crab aggression is not only upsetting to owners, but it can be deadly to crabs. When crabs become aggressive, they typically attack other crabs by pulling at them with their pinchers.

Crabs sometimes flip other crabs onto their backs in an attempt to ward off the victim crab’s defensive pincher. A great many crab fights are actually shell fights, where one crab tries to steal the shell of another crab. The aggressor crab tries to pull the victim crab out of his shell by grabbing with a pincher and pulling.

In defense, the victim crab will withdraw into his shell as far as he will go. If the aggressor persists, the victim crab may drop a limb in an attempt to dislodge the aggressor’s grip. Crabs sometimes fight for reasons unknown to their human caretakers, attacking each other’s eyes, antennae, and limbs.

The result can be severe injury that can result in infection and ultimate death for the losing crab. If you see one of your crabs engaging in aggressive behavior toward another crab, separate the two immediately. Put the aggressive crab in a dark, quiet place, such as a small molting tank or a travel carrier.

Let the crab calm down before you return him to the enclosure. If the aggression persists and seems to be a shell fight (the aggressor is trying to pull the other crab out of his shell), separate the two again, but add more shells to the enclosure before you return the aggressor.

If the crab who wants a new shell has more empty shells to choose from, he is more likely to stop harassing other crabs. Another way to discourage aggression among crabs is to provide them with more room. Giving them a bigger crabitat to roam through will help reduce incidences of territorial aggression.

Hermit crabs who persist in attacking other crabs for no apparent reason, or regardless of the number of vacant shells in the enclosure, should be permanently separated from the group. You may have to start another crabitat to keep the offending crab away from the crabs he is harassing. Since even aggressive crabs shouldn’t live alone, be sure to give him a friend or two who are his size or bigger, to discourage further aggression.

Crab Sounds

Long-time hermit crab owners are familiar with a sound made by crabs when they are picked up or when they get into altercations with other crabs. Known as chirping by pet owners, and more technically referred to as stridulation by biologists, this vocalization sounds like an odd combination of noises, including a frog’s croak and a cricket’s chirp.

Scientists believe stridulation is created when a hermit crab rubs certain parts of his body together. You won’t see your crab doing this (this vocalization is so mysterious, scientists are not completely sure how it happens), but you will hear the resulting sound. Another sound familiar to crab owners is the clicking made when hermit crabs knock their shells together.

Unlike stridulation, these clicking sounds are made inadvertently and usually happen when crabs are gathering in a food dish, climbing up a decoration en masse, or basically doing anything that brings them in close proximity to each other.

Hiding

In the wild, hermit crabs hide as a way to avoid predators. Hiding helps a hermit crab feel secure and reduces the animal’s stress level. Hermit crabs have two ways of hiding: in their shells and in an external hiding place. Because they carry their shells around with them, hermit crabs can easily hide at a moment’s notice if they feel threatened.

They withdraw as deeply into their shells as possible, covering the shell entrance with their large pincher to block off the opening from an intruder. (Hermit crabs who are living in shells that are too small will have trouble fitting all the way into the shell when they retreat.) In nature, hermit crabs take hiding one step further by finding places they can hide in while they are retreating into their shells for sleep.

This can be a pile of leaves, a coconut shell, a clump of rocks, or anything they can find that seems to provide security. To help pet hermit crabs feel secure and stress-free, it’s important to provide hiding places in their enclosure. Commercial reptile hiding places work great for hermit crabs, as do half-buried terra cotta pots and the bottoms of 1-liter plastic soda bottles. If you provide your crabs with roomy hiding spots, you’ll likely see them gathering together to sleep inside one of these protective covers.

Shell Swapping

One of the most amusing of hermit crab behaviors is the phenomenon of shell swapping. This is when one hermit crab abandons his shell in favor of another one, causing a chain reaction of shell changes that races through the crab population. If you are lucky, you’ll see this amusing game of musical shells take place. If you happen to see one of your crabs changing shells, pay attention. All the other crabs in the enclosure might start switching, too.

Sean B.

Hi, My name is Sean. I’m blogging mostly about freshwater and saltwater aquariums, fish, invertebrates, and plants.