Home » Is My Hermit Crab Male Or Female? (Sexing Hermit Crabs)
is my hermit crab a boy or girl?

Is My Hermit Crab Male Or Female? (Sexing Hermit Crabs)

The first thing we do when getting a hermit crab is to give it a name. This may involve finding out how to tell if a hermit crab is male or female. Sexing hermit crabs isn’t easy as gender differences can be comparatively subtle.

The easiest way to sex hermit crabs is to check their legs. Male hermit crabs have hairy legs; females have smooth legs. You can check the hermit crab’s genitals. Females have two tiny sexual organs, called the gonopores, atop their third set of legs. Young males also gain size and mass faster than females.

Owners shouldn’t encounter any breeding issues due to hermit crab gender. It’s safe to pair them in opposite-sex groups as captive hermit crabs rarely mate. All the same, learning how to sex hermit crabs is an interesting process.

Is My Hermit Crab a Boy or Girl?

How do you know if a hermit crab is male or female? You will need to get a look at your hermit crab out of its shell. Never wrench a hermit crab from its home for gender identification.

Some physical characteristics are almost identical between male and female hermit crabs. For example, it’s impossible to tell boy and girl hermit crabs apart by claw size. Some say that females have larger claws, but there is no scientific basis for this claim.

Instead, you will need to review physical characteristics and, to a lesser extent, behavior. Once you know what you are looking for, sexing hermit crabs will become second nature. All the same, differences can be subtle, so it may take more than just a cursory glance.

Physical Appearance

In many species, the size of an animal can be used to detect sex. Usually, the male is larger unless the female needs to carry sizeable embryos. This isn’t relevant to adult hermit crabs. Once grown, hermit crabs stay about the same size.

There are some discrepancies, especially when young. Hermit crabs grow and molt at different rates based on sex. Male hermit crabs grow quickly, regularly molting. So, a young male may tower over a female of equivalent age.

Females grow slower as hermit crabs breed while young, usually in the first year of life. This is a matter of survival. Females carry their young in an egg sac attached to their legs, which makes them vulnerable. By growing more slowly, a female is likelier to find suitable shells to hide within.

During mating season, male hermit crabs can grow in size. Many males molt ahead of mating and emerge larger. This does not make them any more appealing to females, though. It just gives them a better chance of overpowering rivals for a potential mate.

Where physical appearance differs is the legs. Male and female hermit crabs have 10 legs. In females, these will be completely smooth. In males, the legs are covered in coarse hairs.

Additionally, females have 3 appendages on the left of the abdomen. Males lack these. These appendages (pleopods) double as a sac for a female to carry her unborn young.

Sexual Organs

Genitals are the most failsafe way of identifying sex in an animal. It’s the same with hermit crabs, but you need to know what you’re looking for.

Male hermit crabs have a penis below the fifth set of legs. The Royal Society Open Science claims that this organ can be disproportionately large compared to body mass. It can be as large as 60% of the hermit crab’s body length. This is an evolutionary tactic to protect the shell.

As discussed, males grow faster than females. This makes appropriately-sized shells a rare commodity. To avoid losing their shells, male hermit crabs develop a large penis. This enables the male to mate without vacating his shell, otherwise leaving it available for a rival.

The sexual organs of the female are called the gonopores. These are two tiny openings located above the third pair of legs. When we say tiny, we do mean tiny. You may need a magnifying glass to identify gonopores.


There are some obvious differences in temperament between male and female hermit crabs. It’s inadvisable to rely on watching their behavior to sex hermit crabs. There are a handful of variations, though.

In some cases, females are more confident and outgoing. Females are likelier to explore new terrain. They may also find a range of different hiding places. Males are more likely to find one location and stick with it as they feel safer this way.

While this can be linked to basic survival instinct, it may also pertain to mating. According to Biological Sciences, hermit crabs with high fecundity breed less. This is due to higher rates of mortality associated with risk-taking behaviors.

More cautious males tend to enjoy greater success with breeding. Remaining careful helps hermit crabs live longer and enjoy more mating cycles.

These mating rituals may lead to other conduct between sexes. Sexually mature males guard females that they’re interested in breeding with. As explained by Behavioral Ecology, this can lead to conflict.

If you see several hermit crabs surrounding each other, the object of attention is likely female. The interested parties will be males hoping to curry favor. As captive hermit crabs rarely breed, this approach is unlikely to see results.

how to tell if a hermit crab is male or female

Male vs. Female Hermit Crabs

There are differences in appearance and conduct between male and female hermit crabs. This table summarizes the core variations between the sexes. Here’s how to sex a hermit crab at a glance:

Male Hermit Crab Identification:Female Hermit Crabs Identification:
Hairy legsSmooth legs
No legs on the abdomenLegs on the left of the abdomen
No abdominal appendagesThree feathery appendages left of legs to carry eggs
Has a penis below the fifth set of legsHas gonopores atop the third set of legs
Increase size and mass in mating seasonSize remains consistent in mating season
Grow in size quickly from a young ageSlowly and steadily increase in size with age
Keen to reproduce during mating seasonRarely receptive to mating in captivity
No sexual pheromonesReleases pheromones if receptive to mating
Attracted to larger femalesIndifferent to the size of males
Stick to familiar terrainSeek a variety of different habitats
Remain shy and cautiousCan be bolder and braver

With over 800 different species of hermit crabs, variations will occur. Following this guidance will enable you to sex a hermit crab. Just do not be alarmed or surprised if you find that your initial perspective was mistaken.

Do Hermit Crabs Change Sex?

Some owners claim that their hermit crabs change sex during their lifetime, but this is unproven by science. It’s more likely that changes to physical appearance led to mistaken identity.

Despite this, hermaphroditism is common in invertebrate species. For example, if a clownfish is born a male, it can change sex irreversibly if it wants to become a school’s dominant female. Oysters and shellfish, closer relatives to the hermit crab, do the same thing.

All the same, hermit crabs are not believed to change sex. The Journal of the Marine Biological Association of the UK confirms they can be intersex, though. These hermit crabs live as males after molting. The gonopores close, and the hermit crab mates as a male.

Do Male or Female Hermit Crabs Make Better Pets?

There is no reason to believe that sex influences the quality of hermit crab companionship. The fact is, most sellers are ignorant of gender. Even experts sometimes get it wrong when assigning sex to a hermit crab.

Be wary of anybody that claims that one sex is superior. This will likely be a sales tactic to influence a purchase. There are no clear and distinct advantages of one hermit crab gender over another.

Can Male and Female Hermit Crabs Live Together?

The Journal of Ethology confirms that hermit crabs can detect sex within their species. This becomes increasingly apparent in the wild during mating season. Males will ignore each other while actively seeking out females.

Hermit crabs cannot be spayed or neutered. In most animals, this is a cause for concern. It suggests that the two sexes shouldn’t be housed together. In reality, captive hermit crabs rarely mate. It takes a particular environment and skilled handler to get this to happen.

Females must be willing to mate with an eligible male. As per the Journal of Crustacean Biology, males cannot force mating with disinterested females. Larger hermit crabs have no biological advantage when it comes to reproduction. Invariably, a larger hermit crab will win this contest.

With this in mind, there’s no harm to pairing mixed-sex groups. Despite their name, hermit crabs are a social species. They like to live in colonies and groups. Denying this opportunity on the grounds of sex leads to loneliness.

Sexing a hermit crab requires close attention. Wait for the hermit crab to emerge from its shell. When it does so, assess its legs. If they’re hairy, you have a boy. If not, it’s a girl. Beyond this, you’ll need to determine its genitals.