Hermit Crab Aggression: Will a Bigger Hermit Crab Kill a Smaller One?

Last Updated on December 17, 2021 by cmoarz

Will hermit crabs kill each other if they are placed in the same tank? Do hermit crabs kill each other if one is larger than the other? Can hermit crabs kill each other? Are they even capable and strong enough to do that?

This article will dive into the fascinating world of hermit crab behavior. You will learn about all the different types of aggressive behaviors between crabs, their size difference, and what they do to protect themselves against it.

Right off the bat, Are hermit crabs capable of killing each other, and do they do so? Yes, they do.

Most hermit crabs are social in nature, with fairly low aggression. They usually live in groups of 5 or more and you won’t see too many issues. However, not all crabs get along, and when they don’t it can become a big problem.

Hermit Crab Aggression, Why Do Hermit Crabs Kill Each Other?

Usually, the reason for such conflict is resources such as shells or food, but in some cases, it can be out of pure aggression for no apparent reason.

There are several different species of hermit crabs, and all have slightly different temperaments. Some will be more territorial and aggressive than others.

Hermit crabs use pinchers to grab each other by the shell and pull and twist until one crab is damaged. This leaves the crabs vulnerable to attack from other predators.

The biggest hermit crab in a group is usually the dominant one, and will typically win any conflict. The smaller hermit crabs will typically back down, but if they don’t, they can be killed.

Hermit crabs are also scavengers and will take any opportunity to get a free meal. This includes digging up their recently molted friends and eating them.

So if you ever wondered do hermit crabs eat each other, the answer is yes they do. One hermit crab can eat another and they often do. It’s an easy lunch when you’re just trying to survive.

Especially when your target is a soft pink recently molted hermit that can’t defend itself and is trying to hide in the sand.

Can You Put Big and Small Hermit Crabs Together?

Yes, and in fact, it’s important that a hermit crab is never left alone and should have others of its species live alongside it. As social creatures, they can die of loneliness if this rule isn’t followed.

As for size differences, it rarely matters. The large crab will become the dominant crab and will have no reason to fight or kill the smaller crabs for the most part as territory and feeding hierarchy will have been established already, and adhered to by the smaller crab.

The only caveat is the substrate should be deep enough for the largest crab to fully burry itself with a bit of space left beneath.

In addition, If you add a new crab to the aquarium it may take some time for them to adapt. The new ‘pecking’ order will need to be established which is normal.

You may notice slight aggression during this phase but will soon give way to more fun social interactions among all of your hermit crabs.

If you are ever unsure whether or not your hermit crabs can live together, it is always best to ask an expert.

They will be able to guide you and make sure your hermit crabs have the best environment possible in which to thrive and live a long, happy life.

But in most cases, if they are the same species it’s usually fine.

Why Did My Hermit Crab Kill the Other?

Hermit crabs kill for a lot of reasons. Hunger, Territory, And even hate between species. Different species don’t always get along and slight variations in the same species can lead to some crabs being killed.

The aggression level of a hermit crab is often the biggest factor in determining whether or not it will kill another crab, and what species they are matters quite a bit also.

Some hermit crabs may be aggressive by nature and this can cause them problems with their own kind. However, even if you get crabs of the same species, it can still be a problem.

All hermit crabs are different, and each reacts differently to other hermit crabs in its vicinity.

For example, one crab may become territorial and see another crab as a threat to its space, while another sees it simply as competition for food and will hunt the weaker crab.

Difusing Aggressive Acts, How To Stop Hermit Crabs From Fighting

There are some things you can do to lower the aggression level in your hermit crabs and stop them from fighting.

While it won’t be perfect And stop all fighting, it should lessen the number of noticeable incidents of violence.

Provide adequate space for your crabs: While hermit crabs don’t need a lot of space, they do need more than is normally provided in their enclosure.

They like to be able to retreat into their shell and be partially buried in the substrate.

If there’s not enough room for them to do this, it can lead to fighting between crabs who are attempting to defend what little territory they have.

Add more hermit crabs: While it might sound counterproductive, this will help to establish a pecking order and reduce the aggression level of each crab.

Make sure they are well fed: If your crabs are hungry, they’re more likely to fight over food.

This often leads to the weaker, hungrier crab being injured or killed by the stronger crab who views it as an easy meal.

A well-fed crab is less likely to bother hunting for its own food and will instead spend most of its time resting in its shell or doing other crab things.

Keep your crabs healthy: A healthy crab is a content crab.

If one of your crabs is sick or injured, the others will see it as an easy target and may even kill it.

Keep your tank clean and your water parameters in check. Dirty water and poor water quality can lead to increased aggression among your crabs.

When they’re stressed, hermit crabs are more likely to fight as a way of releasing that energy.


Owner of AquariumGravel.com and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!