Male vs Female Crab - How do you differentiate

Male vs Female Crab – How do you differentiate?

Luckily, sexual dimorphism regarding the abdomen flap of crabs is the main difference between male and female crabs. Male crabs have a T-shaped apron, while female crabs have a U-shaped apron on the underside of their bodies. Also, males have thicker and larger claws, but females have thinner and smaller claws.

So, it is an exciting job to contrast male vs female crabs. Moreover, pet owners and biologists need to find the gender of their crabs. And, of course, many characteristics and unique traits clearly define which crab species is male and which is female.

Keep reading this guide to learn about the difference between male and female crabs. So… Here we go!

Male vs Female Crab – Quick Review Table:

Before sketching the description to help you distinguish between male and female crabs, I have organized a quick review table. Have a look at the following table for a better understanding!

CharacteristicsMale Hermit CrabsFemale Hermit CrabsReliability of Traits
Reproductive organs:Male crabs have gonopods, which are specialized reproductive organs.Female crabs have broader Abdominal Flaps compared to males.High (100%)
Abdomen flap:In males, it is shaped like an inverted letter ‘T.’Bigger and rounder in females.High (100%)
General size:Large in size.Relatively more diminutive in size.Low (50%)
Size and Color of Claws:Male crab claws are typically larger than those of females.The color of male crab claws often appears brighter or more vibrant than females.Female crabs have smaller claws, and the color of their claws is rough and light.High (100%)
Dimorphism of Claws:Males have different-size claws.Typically larger and bulkier.They have specialized structures for holding onto females during mating.Generally, they have more petite and more slender claws.Mostly same-sized claws.It may be adapted for carrying eggs or other specific tasks related to reproduction.High (80%)
General Color:Males are more transparent and colorful.Females are less bright.Low (50%)
Aggressive behavior:Males are more aggressive.Female crabs are relatively less aggressive.Low (70%)
Taste:Male crab meat is often described as slightly more robust and savory than female crab meat.The taste of the meat of female crabs is sweet, tender, firmer, and flakier.High (100%)
Shedding Shells:Male crabs shed their 20 times.Female crabs shed their shells 18 times.Low (50%)
Mating behavior:Males are more active and keen in mating behavior, even in captivity. They don’t bother whatever the environment is.Female crabs do not like to mate in captivity. These crabs are also less active and interested in the mating process.Low
Which one is more meaty?More meaty (larger size)Less meaty (small in size)High (100%)

You can also read this helpful guide about how to tell if a hermit crab is male or female.

Male Vs. Female crab – All Key Differences Highlighted:

It’s not difficult to differentiate between a male and a female crab. Let me explain every characteristic that will help you to tell the gender of a crab.

Male vs Female Crab – Physical Differences:

Let’s see what the physical differences between Mr. and Mrs. Crab according to the research of the Frontiers in Organization:

  1. Abdomen Shape:

Even though both males and females have the same number of segments in their abdomens across species, their abdomen shapes can differ due to sexual dimorphism. And sometimes, segments can fuse together in some instances. Let’s see what the difference is between the abdomen of a male and a female crab.

  1. Abdomen of Female Crab:

In female crabs, the lower belly apron resembles the graceful curve of a bell. Their abdomen expands, taking on a rounded and highly domed shape. Then, it transforms into a specialized brood pouch. This region is also referred to as the undercarriage.

In contrast to males, females allocate a considerable amount of energy towards enlarging their abdomen. This body section is an incubation chamber for eggs and newly emerged offspring. The eggs are fully shielded and protected from external interference when the abdomen is sealed shut.

  1. Abdomen of Male Crab:

In males, the lower belly apron typically resembles an inverted letter ‘T.’ Since its primary role is safeguarding the gonopods for reproduction, their carapace experiences faster growth than the abdomen. In certain species (like Scylla spp.), the abdominal flap of mature females notably darkens as they reach a certain level of maturity.

2. Reproductive Organs:

According to the ResearchGate study, most crab species exhibit sexual dimorphism. This physical characteristic makes it possible to determine their gender externally.

Crab owners can gently pull the abdomen from the underside, revealing the crab’s reproductive organs. This method helps determine the crab’s gender. In male crabs, there are always just two pairs of special swimmerets or pleopods called gonopods.

These remarkable swimmers are explicitly designed for mating. Furthermore, these gonopods can vary in length. And at the junction of the two segments, there’s typically a tiny flap that can resemble a cup.

3. Size and Color of Claws:

This method can also be a reliable way to differentiate between males and females in certain crab species. Adult male crabs typically have broader and longer claws than females with similar carapace lengths. This difference in claw size is often used to confirm sexual dimorphism.

Unlike females, males prioritize investing energy in growing their claws. The larger claws are crucial for various activities, including fights, courtship, mating, defense, and protecting females during copulation. This preference for large claws in males is driven by sexual selection, as females are more inclined to choose males with larger claws.

You can take Fiddler crabs (genus Uca) as an example. Here, intense sexual selection by females results in exaggerated male traits. These males are lopsided, sporting one significantly enlarged claw and one smaller claw, while females possess two tiny claws.

Interesting Fact:

Do you know? The most popular way of differentiating crabs’ gender is through the color of their claws. Most of the time, masculine crabs have blue claws. On the flip side, female crabs have red claw tips.

4. General size:

Crabs are sexually dimorphic!

In the majority of crab species, adult males tend to be more prominent on average than females. This size difference is also linked to females prioritizing investment in reproduction rather than growth. Moreover, it’s important to note that there is variation around the average size of each sex.

Age also plays a role in determining their length. So, it contributes to the size variability among individuals within each sex. As a result, for many species, there is a significant overlap in size between males and females.

Certain crab species, like the Thai Micro crab and Red Apple Crab, can be incredibly small. They require specialized tools to distinguish between genders. Their diminutive size poses a challenge for visual differentiation.

For the untrained eye, it’s generally not possible to visually differentiate between genders in most other cases. This method of sexing crabs is typically only applicable to larger species.

Male crabs commonly have faster growth rates than females. So, rendering body size alone is an unreliable indicator of adult crab sex. Hence, it’s advisable not to depend solely on this characteristic for sex determination.

5. Coloration:

Numerous crab species demonstrate sexual dichromatism, where males and females exhibit distinct coloration. In such cases, male crabs typically display more incredible vibrancy or ornamentation than females.

Sexual selection has two primary categories:

  1. Traits serving as weapons (such as claws, size, speed, etc.).
  2. Traits acting as ornaments to captivate female attention (such as coloration).

Female crabs have subdued colors. This helps in predator avoidance and enhances their reproductive success by reducing their visibility to predators. This strategy allows them to reproduce more effectively. In males, colors can effectively work as a caution to potential rivals or assist individuals in identifying members of their kind.

However, this characteristic isn’t fail-safe. So, coloration can also vary depending on the crab’s life stage. For instance, as crabs prepare to molt, their color becomes similar (less vibrant and less intense) as they prepare to molt.

Male vs Female Crab – Behavioral Differences:

Let’s find out what behaviors stand male and female crabs apart:

1.Mating Behavior:

Typically, the male will invert the female and encircle her with his claws and legs during mating. They stand facing each other, with the male crab positioned atop and gripping the female beneath him with his walking legs.

At this point, the female extends her abdomen. She starts revealing her gonopores to enable the male’s gonopods to be inserted for semen transfer. However, a significant issue arises as crabs are inherently aggressive creatures.

This nature makes them appear to the untrained observer as if they are fighting rather than mating. Still, you can differentiate the gender of a male and a female crab with the help of their mating behavior.

After Mating in the Wild:

Female blue crabs migrate southward after mating, whereas male crabs stay within estuaries. Male blue crabs reside in the upper estuaries, digging into soft mud and seeking shelter among seagrasses.

Their solitary nature shields them from predators, yet it poses a significant challenge to their survival. They are vulnerable to low oxygen levels and pollution from various sources.

2.Aggressive Behavior:

Do you know male crabs are more aggressive and angry than female crabs? More specifically, male crabs frequently drive off intruders or engage in active combat with other male crabs.

However, it doesn’t mean female crabs are shy or peaceful creatures; they are just less aggressive than male crabs. Regardless, it’s advisable to house multiple crabs in groups consisting of one male and numerous females. Therefore, it’s crucial to determine their genders accurately.

Male Vs. Female Crabs: Life Span

Male and female crabs have different lifespans. Female crabs generally have a shorter lifespan, while males tend to live longer. This phenomenon is primarily attributed to the energy-intensive reproduction process in female crabs.

Female crabs invest significant energy into producing and nurturing eggs, which can affect their overall health and longevity. In contrast, male crabs do not bear the same reproductive burden. Thus, they tend to have a comparatively longer lifespan.

However, it’s essential to note environmental factors. For example, habitat quality and predation influence the lifespan of both male and female crabs.

Male vs Female Crab – Growth Rate:

Male and female crabs have different growth patterns. Male crabs are known for their rapid growth. This is because they undergo frequent molting as they grow larger. This fast growth is attributed to their need to compete for mates and establish dominance within their social hierarchy.

In contrast, female crabs tend to grow at a slower pace. This is partly due to the energy they allocate towards reproduction. As female crabs can start breeding as early as their first year of life, they grow slowly. The reproductive investment and early breeding behavior of female crabs can hinder their growth rate compared to their male counterparts.

So, male crabs are mostly larger than their female counterparts due to their faster growth rate. Additionally, as I mentioned, there are visible physical differences between male and female crabs.

Economic Importance of Male vs Female Crabs:

Understanding the distinctions between male and female crabs is crucial in the fishing industry. While female crabs generally have less meat and smaller sizes compared to males, they play a vital role in maintaining crab populations through reproduction.

To manage crab populations sustainably, some regions enforce laws and regulations limiting the harvest of female crabs. The restriction of illegal harvesting of female crabs ensures their continued presence for reproductive purposes and long-term population stability. Otherwise, crabs will soon disappear from this world!

You could be interested in watching an informative YouTube video of Julie Lively, a fisheries specialist with AgCenter, on identifying male and female crabs.


1.Are Male Or Female Crabs More Expensive?

Male crabs are more expensive online and offline than female crabs. Male crabs are purchased at $75 to $75 per dozen, while female crabs are sold at 56 cents to 85 cents per dozen.

However, if you want to put them in homes, the male or female pet crabs are more expensive than wild crabs sold at stores for cooking purposes. Nevertheless, it’s important to note that the price discrepancy is relative and can vary based on cultural factors.

2.What physical differences differentiate a male and a female crab?

Apart from the physical differences mentioned in the first section of this guide, male crabs have hairy legs. They use these legs to grip onto their shells and fight during competition for mates.

In contrast, female crabs typically have smoother, hairless legs. These physical characteristics contribute to the distinct appearances of male and female crabs.

3.Do crabs have three genders?

No, crabs do not have three genders. Most species of crabs have sexual dimorphism, meaning they have distinct male and female sexes. Some species have specific characteristics (or Behaviors) that vary between individuals. Still, they fall within the typical male-female binary classification in terms of reproductive roles and anatomy.

4How do chelipeds tell the difference between male and female crabs?

Chelipeds are crucial tools for crabs, consisting of the propodus, merus, and dactyl. They serve various purposes, including feeding, defending territory, and protecting the crab from predators. But do chelipeds clearly tell the gender of a crab?

You can find the gender of a crab, especially mud crabs, by examining their chelipeds. Male crabs often have larger chelipeds compared to females. So, males have larger dimensions in dactyl length, propodus length, and propodus width. ~ Source


In conclusion, finding the gender of the crabs is not only crucial for selecting suitable names, but it is also for understanding their behavior and reproductive tendencies. As a result, it allows us to be better prepared for their care and breeding. Always remember that general size, claw dimorphism, coloration, behavior, etc., should not be the dependable methods for determining the sex of crabs.

In certain species of crabs, these traits provide a helpful indication, but they are only sometimes accurate. Hence, it is advisable to use them in conjunction for a more reliable result (crab gender).

However, there are only two definitive methods to distinguish the gender of crabs accurately – the presence of gonopods and the shape of the abdomen. Females exhibit a significantly broader abdominal flap compared to males. So, that’s all for today!

You may also be interested in reading the posts about hermit crabs:

Have happy hermies!