Home » Why Do Hermit Crabs Attack Each Other? [6 Common Causes]
hermit crabs aggressive towards each other

Why Do Hermit Crabs Attack Each Other? [6 Common Causes]

(Last Updated On: October 20, 2022)

Hermit crabs are social animals in the wild, living in substantial colonies, and they like to replicate this arrangement in captivity. This means they usually get along with each other.

Hermit crabs playfight in several ways, including wrestling or fencing with antennae, pushing one other, and climbing on each other. Even disputes over shells can sometimes be resolved amicably. Sometimes, what started as a playfight can result in physical aggression.

Common reasons for hermit crabs fighting include asserting social dominance, claiming territory, battling for the right to mate, or winning a coveted shell. Hermit crabs that grow overstimulated due to external noise can also grow aggressive.

The most obvious sign that two hermit crabs are fighting is the active use of chelipeds and pinching, especially attempting to sever eye stalks. If you notice these aggressive behaviors, the hermit crabs must be separated before one or both are seriously hurt.

Minimize the risk of hermit crabs attacking each other by providing a large enclosure where each hermit crab has its territory, providing a selection of spare shells, and avoiding external stimulation.

Are Hermit Crabs Aggressive Towards Each Other?

Hermit crabs have a well-earned reputation and friendly and docile animals. You can put several hermit crabs in the same habitat, as they enjoy the company of conspecifics. 

Despite this, conflict can arise between hermit crabs. Social hierarchy is important to hermit crabs, and your pets may clash over alpha status. Thankfully, most hermit crabs prefer to settle disputes peacefully, often through play fighting.

Hermit crabs play fight for recreation in several ways, including:

  • Wrestling with antennae
  • Pushing each other over
  • Climbing on each other

If the hermit crabs are playing, they’ll take turns acting as aggressors. Equally, if a hermit crab is knocked onto its back, it’ll be helped up, or if it chooses to hide, the other hermit crab will walk away.

What Does it Look Like When Hermit Crabs Are Fighting?

While playfighting is natural for hermit crabs, outright aggression must be identified and stopped. You’ll be able to tell the difference when chelipeds become involved.

If two hermit crabs actively fight, they’ll start pinching – not just pushing and rocking. More importantly, the claws will be directed at delicate parts of the anatomy, most notably the eye stalks. If hermit crabs attempt to sever eyes, they’re no longer playing.

Listen for any noises from a hermit crab enclosure. If your pets are contentedly going about their business, you may hear a low, regular chirping. Increasingly loud, desperate chirps suggest that at least one hermit crab is afraid or upset.

why is my hermit crab aggressive?

Can Hermit Crabs Hurt Each Other?

If a hermit crab conflict becomes genuinely aggressive, injuries become more likely.

Hermit crabs may lose limbs during a fight. Some hermit crabs deliberately shed a leg or lose a claw to escape or distract an opponent.

Even if hermit crabs make an active choice to shed, it won’t be a positive experience. Applied Animal Behavior Science confirms that hermit crabs can feel pain and may choose to shed as the lesser of two unfavorable situations.

Do Hermit Crabs Fight to the Death?

If your hermit crabs are left to fight indefinitely, there’s always a risk that one of them won’t survive the conflict. Even if the fight doesn’t end a life, the stress it causes may be fatal.

Can Hermit Crabs Avoid Fighting?

Unless both hermit crabs are aggressive, one will likely be less interested in doing battle than the other. The victim of the attack will avoid a fight if possible.

Most hermit crabs avoid conflict by hiding in their shell. This sometimes works, as the aggressor may rap upon and rock the shell for a while, eventually growing bored and moving on. If a hermit crab is particularly hostile, it may drag the victim out by force.

To avoid this outcome, hermit crabs may climb the walls of an enclosure and aim to hang from the ceiling. The Journal of Ethology explains how this behavior is typical in the wild, and such instincts can be carried over into captivity. 

Why Do Hermit Crabs Fight Each Other?

Some hermit crabs are grumpy and ill-tempered by nature. Hermit crabs are wild animals at heart; some will struggle to adjust to a life spent in captivity and the frustrations that come with that.

While stress and unhappiness can explain why a hermit crab grows agitated and cantankerous, there will often be a direct explanation for aggression.

Consider if any of the following circumstances apply:

1/ Stress

Hermit crabs are easily stressed in captivity, and prolonged anxiety can take its toll on behavior. As an owner, you have a duty of care to your hermit crabs to provide a stress-free environment.

If your pet hermit crabs are growing agitated, check the following.

  • Is the habitat an appropriate temperature – no cooler than 72OF, no hotter than 84OF? 80OF.
  • Does the habitat have a humidity level of 80%?
  • Are your hermit crabs enjoying a diet rich in protein?
  • Do the hermit crabs have enough entertainment to avoid growing bored?
  • Is the habitat clean, and can your hermit crabs bathe daily?

The wrong habitat can make hermit crabs increasingly miserable, and hermit crabs are likely to act out when they’re unhappy. Keep working on creating the optimum living arrangement for a harmonious life.

2/ Social Hierarchy

No matter how many hermit crabs you keep in a tank, one of them will become the alpha. This is a natural behavior for hermit crabs, who will automatically arrange themselves into a social hierarchy.

The advantages of holding alpha status in a hermit crab colony include the first refusal of food and new shells. Typically, the largest hermit crab in a tank will automatically assume alpha status, though others may challenge for the honorific.

Hermit crabs are likeliest to fight for a higher place on the social ladder after molting. When hermit crabs molt, they increase in size and regrow lost limbs.

This can embolden a previously submissive hermit crab into issuing a challenge, politely or otherwise.

3/ Territorial Disputes

In the wild, hermit crabs have an entire beach to traverse, so there’s lots of space for every hermit crab to care out territory to call its own. Squeezing multiple hermit crabs into a 10-gallon tank is a significant lifestyle change.

As all your hermit crabs will look to burrow under the substrate to sleep and molt, they’ll appreciate territory to call their own. If your pet hermit crabs feel too cooped up, the risk of aggression becomes increasingly pronounced.

Combat this by providing the most extensive accommodation for your hermit crabs. 10 gallons may be large enough for a small number, but consider extending to 20 gallons if you have more than five hermit crabs in your care – and add more substrate.

4/ Right to Mate with a Female

Female hermit crabs are unlikely to breed in captivity but still enter season. When fertile, a female releases pheromones that attract the males in the tank. Male hermit crabs may fight over the right to mate.

Often, the alpha hermit crab will invite the female to breed. She’ll likely decline this invitation by hiding in the shell, but the male will still ‘guard’ his love interest. This entails following the female around and threatening any competitors to stay away.

Most male hermit crabs will acknowledge when a female is being guarded and keep their distance, especially if the animal that wants to mate grows aggressive in its determination.

Consider separating the female and guarding the male against the rest of the tank for a few days. The female hermit crab will leave her season and stop releasing pheromones after three or four days, at which point the male will cease guarding and become docile once more.

hermit crab fighting behavior

5/ Shell Wars

Hermit crabs will often come into conflict over coveted shells. A shell is a hermit crab’s home, providing shelter and safety. All hermit crabs want the finest shell they can lay claim to.

If a hermit crab covets the shell of another, it’ll challenge it by rapping upon the vessel. If the incumbent hermit crab agrees to this contest, the two animals will indulge in antennae wrestling. The result of this is usually accepted with good cheer.

Unfortunately, some hermit crabs can grow aggressive in pursuing a shell, including dragging an owner out by force. This behavior cannot be permitted, as it causes significant distress – and risks injury – to the owner of the shell.

Providing spare shells in a habitat will minimize the risk of these encounters. If all hermit crabs feel their needs are met, they are less likely to attack a conspecific.

6/ Overstimulation

We mentioned how stress could cause hermit crabs to behave erratically; the same applies to overstimulation. Noise is the likeliest culprit here. Be careful about playing loud music in the vicinity of hermit crabs, as it can make them erratic.

General noise can also upset hermit crabs, including raised voices and heavy traffic outside. Hermit crabs don’t have ears, so they ‘hear’ through hairs on the legs. If a hermit crab’s sense of danger is pricked but can’t pinpoint a threat, they may turn on each other.

What To Do If Your Hermit Crabs Are Fighting

If your hermit crabs are fighting, they should be separated at once. You should wear gloves while doing this, as you may be pinched in confusion. Aggression is uncommon in hermit crabs, so when their blood is up, they act out of character.

You should always have a spare tank if you keep hermit crabs, so you can relocate your pets while cleaning a habitat. Relocate and isolate an aggressive hermit crab in a dark room to allow it to cool off.

Don’t leave a hermit crab alone for too long. As social animals, living without company will make a hermit crab’s behavior even more problematic. If your hermit crab’s aggression was a one-off, add it back to the main tank and observe interactions.

You may find that the dynamics in your hermit crab habitat change after a fight. Behavioral Ecology and Sociobiology said that hermit crabs base their interactions on previous experiences with individuals.

Conflict between hermit crabs is rare, but it happens. Ensure you understand the difference between two hermit crabs playfighting for recreation and attempting to kill each other.