Did you know that each and every Hermit Crab has their own little personality! Thats right, some are shy, and some are outgoing and some just don't get along with anyone. They are known to show many different personalities and behaviours both in the wild and in captivity.
Below we will explore what these behaviours are and what they mean.
Shyness and Hiding Some captive Hermit Crabs are awfully shy and prefer not to come out and about when humans are close by the tank, preferring to adventure out at night to eat and do their activities. They may spend a lot of time in hiding and scuttle away quickly when someone approaches their tank. This is a completely normal behaviour, especially in crabs that are new to captivity. This is known as Post Purchase Syndrome (PPS), when a Hermit Crab is moved from a pet store to their new captive tank, they will be undergoing huge amounts of stress and will often burrow down into the substrate or go into hiding to distress. You should never force a shy or hiding crab to come out and socialize, it is vitally important that you offer them hiding places so that they can feel safe and secure.
Digging When Hermit Crabs dig, it's not just for moulting purposes. Hermit Crabs will often dig down into the substrate to distress when arriving at a new tank, sometimes they will dig for fun or activity, sometimes they will dig to find a great spot for a moult, and sometimes they will dig down to get away from unwelcome conditions such as too hot, too cold or too dry. None the less, excessive digging is not something to worry about and is a very common behaviour.
Climbing Land Hermit Crabs are exceptionally good climbers, and climbing is often an activity that they quite enjoy. This is why it is so important to have a secure lid on your tank, because crabs can and will escape if given the chance. In the wild, Hermit Crabs will often climb up high in trees etc. to feel secure from predators on the ground, they often will sleep somewhere up high, which is why it is recommended to offer your captive crabs some objects to climb and keep busy.
Flicking/Pushing You may notice that sometimes when your crabs get together or too close to each other, one may start flicking the other with their legs or pushing them out of the way. This is very normal and usually a way of one crab telling the other to back off and leave them alone. Quite often the larger crabs will flick the smaller crabs when they get to close. This can be a sign of dominance, or annoyance. Something to watch out for, if this turns into a more aggressive disagreement, you may need to intervene.
Antennae Fights An interesting behaviour to watch is when two Hermit Crabs approach each other and brush/wiggle their antennae against the other crab's antennae, they may appear to be moving them quickly and it can come across as aggressive. As long as they are not hurting each other, it is best to leave them be to interact and build on their social skills.
Shell Aggression (known as Shell Jacking) Sometimes crabs may come across a shell that they like, unfortunately, that shell may already be inhabited by another crab. The crab who has found this desired shell, may try to steal that shell from the crab that is housed in it. This is known as shell jacking, and although it can be a common behavior, it is not something that should be treated lightly. The shell jacker will approach the owner of the shell that they like, and knock their own shell against the other crabs, this will cause the crab to come out and see what is going on. The shell jacker will then try to pull the other crab out of its shell by grasping its leg or claw, often the crab will drop its claw or one of its walking legs in an attempt to keep their shell. They would rather lose a limp, than lose their shell. Any attempt at trying to pull a Hermit Crab from its shell will almost always result in a limb loss or the crab being torn in half. They have incredible strength in their abdomen to hold onto their shell and will likely not give up their home when they are forced. The most common cause for this can be due to a lack of available shells in the tank for each Hermit Crab. If you happen to come across a shell jacking in progress, it is important to remove the shell jacker from the situation. You can isolate them for a small period of time with some other suitable shells, perhaps similar to the one that they have tried to steal (both style and opening)
Chirping or Croaking (also known as Stridulation) Hermit Crabs are naturally known as quiet pets, however, sometimes they will make a chirping or croaking sound. This can often be heard if the crab is feeling fearful, in an aggressive situation, discomfort or annoyance. If you do happen to hear chirping coming from your tank, it is best to check it out right away to investigate the cause.
Mating Contrary to belief, Hermit Crabs can and do mate in captivity. Although not common, it does happen. During mating season (summer) Male Hermit Crabs will seek out females to mate with, although the males are keen to mate, it is entirely up to the female if mating will go ahead. She will release a pheromone that announces she is ready to mate, the male will detect this pheromone and approach the female. Males will often fight over who gets to mate with the female, but only she will decide who will be successful in doing so. Mating may appear aggressive, and like the male is trying to remove the female from the shell, Hermit Crabs mate while still wearing their shells to ensure their safety. The male will approach the female and tap, stroke or rock her shell back and forth to encourage her to come out. The male and female will partially come out of their shells and hold each other face to face like a hug; the male will then deposit his sperm into the females gonopores, if fertilized, the female will carry her eggs around until she is ready to drop them into the ocean to spawn.
Shell Alterations Perhaps you have noticed your crab munching on their own shell, or maybe ever so slowly, parts of their shell appear to be disappearing. Hermit Crabs will pick a shell that they like and will often alter it to fit the way they prefer. They will use their claws to pick part of their shell off to make it a more suitable and comfortable fit. This is completely normal and safe behaviour. The only time this behavior is dangerous, is if your crab is wearing a painted shell, during alteration, they may accidently pick off toxic paint and consume it. This is why it is so important to only ever supply natural shells within your tank.
Shell Shopping Just like when you go clothes shopping and try on everything, so do Hermit Crabs! They can be quite picky when trying to find that perfect shell and will often spend hours or days trying on various shells until they find one that they like. This behaviour is normal and not something to be concerned about if you have a large variety of shells on offer in the correct sizes. Eventually your crab will find the perfect shell and will stick with it.
Excessive Exercise Perhaps you have an exercise wheel in your tank, and you have noticed your crab spending hours at a time going around and around. This is because in the wild, Hermit Crabs travel many kilometers a day going from one place to another. It may appear as excessive exercise to you, but to them, it's just another daily journey travelled. Captive crabs often enjoy having a wheel in their tank to keep them busy walking and entertained for hours on end.
Swimming or Bathing Hermit Crabs require deep pools of water so they can fully submerge their shells, this helps them to fill their shells with water to keep their abdomen from drying out. They will also need a deep-water source to drink and bathe themselves. Hermit Crabs will often clean out sand, poo and other debris from their shells while in their pools. Some crabs are toe dippers, and you may never see them fully submerge, and some crabs are obsessive swimmers and will spend hours at the bottom of their pools. As long as you have supplied a safe way in and out of the pools, they can spend as long as they like in the water and will resurface when they are ready.
Shell Dropping A very serious behaviour that should not be taken lightly. Hermit Crabs should never be without their shells, so if they are dropping their shell and making nudie runs around the tank, it's time to take action! Possible causes for shell dropping include, shell jacking victim, not enough appropriate shells on offer, stress, fear, sickness or an unsuitable tank environment. You can read more about naked Hermit Crabs and what to do here https://www.happyhermie.com.au/post/naked-hermit-crab-what-to-do
*Hermit Crab pictured belongs to The Happy Hermie