Fun Red Claw Crab Facts For Kids

Arpitha Rajendra
Nov 03, 2022 By Arpitha Rajendra
Originally Published on Aug 06, 2021
Edited by Luca Demetriou
Fact-checked by Sonali Rawat
Read more red claw crab facts here.
Age: 3-18
Read time: 8.4 Min

The red-clawed crab (Perisesarma bidens) is a crab species of the family Sesarmidae of the Indo-Pacific region. These are mangrove crabs of the genus Perisesarma. As per 2006 data, there are 23 described species in this genus. These crabs are semiterrestrial and a small species that occupy forest floors at low tide. These species will try to eat anything, like pencils and other objects, that does not negatively impact their health. P. samawati was the last species in the genus Perisesarma. They do well in aquariums.

Keeping red claw crabs in brackish water is preferable for them to reach full lifespan in an aquarium. They are also called red crab, Thai crab, and mini crab. The order Decapoda meaning, 'ten-footed,' consists of crustaceans. These crabs are omnivores, and the red-clawed crab is brown-colored with spots. Crabs normally walk sideways due to their legs, the sidelong gait is more efficient for them. The oldest crab fossils found were in Eocarcinus, which is believed to represent a stem-group lineage and lack many physical features of the modern-day crab.

If you like these interesting facts about red claw crab, make sure to check out these sally lightfoot crab facts and Hermit crab facts.

Red Claw Crab Interesting Facts

What type of animal is a red claw crab?

The red-clawed crab (Perisesarma bidens) is a crab species of order Decapoda, infraorder Brachyura, and phylum Arthropoda. They are shy, territorial, aggressive, and skittish little freshwater crabs. These crabs are a nocturnal species and spend most of their time hiding. The aggression of males towards their tank mates depends on the space, and females are not as aggressive. They are scavengers and find food at the bottom of the water bed. They are also pretty good hunters. They are one of the popular aquarium crabs and so well with a good tank setup. These crabs thrive in brackish water and thrive with some salt added to the tank. These mini crabs are excellent escape artists and great climbers. They can escape both from predators and an aquarium.

What class of animal does a red claw crab belong to?

Red claw crabs belong to class Malacostraca.

How many red claw crab are there in the world?

The data on the population of red claw crabs is not available.

Where does a red claw crab live?

The range of red claw crab's natural habitat extends across Indo-Pacific areas from Zanzibar through Fiji and Japan.

What is a red claw crab's habitat?

The natural habitat of red claw crabs includes brackish water, shallow rivers, coastal mangrove swamps, and estuaries that meet the sea. For their burrowing and foraging habits, these crabs need a sand substrate. They can live in freshwater but do better in brackish water (1-2 tablespoons of salt per gal or 3.7 l of freshwater can be added). A 10 gal (37.8 l) tank with aquatic plants, hiding places, driftwood, and aquarium decor is a good environment. A paludarium can also be used as it can hold both land and water environments. Some ranges of paludarium consist of shelves with which you can create sand landmasses.

Who does red claw crab live with?

Red claw crabs are territorial and aggressive. They either live on their own, or one male with two females can be kept in an aquarium.

How long does a red claw crab live?

The average lifespan of red claw crabs is 2-2.5 years in captivity.

How do they reproduce?

It is almost impossible to breed red claw crabs in captivity. The breeding season of this crab from April through September in their natural habitat. A study proved that these species reach sexual maturity at a small size. After releasing the first batch of larvae, the females can reproduce again almost immediately. So, they'll produce two broods per breeding season. The breeding rituals of these animals have not yet been recorded. Males are known to pin the female down after flipping them. The fertilized eggs are incubated for up to 20 days. The babies hatch as larvae from the eggs and also receive no care from the female. Sometimes babies become food to the other red claw crab. They take anything from two weeks to more than one month to complete metamorphosis. The larvae take up to 50-60 days to turn into red claw crabs. The eggs in captivity barely hatch, and those of the eggs that hatch will die almost immediately. One batch can have about 100,000 eggs.

What is their conservation status?

The conservation status of red claw crabs has not yet been evaluated.

Red Claw Crab Fun Facts

What does red claw crab look like?

Red claw crabs vary between red and orange with brown spots on their body. Males have more colors and are brighter than females. Also, males have bright red claws, and females have dark red claws. They have yellow tips on their claws, which change between bright and pale. They have eight legs and two distinct red claws for which they are named. Their eyes protrude out of their carapace, similar to most of crab species. On the lateral sides of their carapace, they have two teeth. The gill chamber of these species is situated close to their first pair of walking legs under the carapace. They can stay out of the water as long as their gills are wet. Even with gills, these crabs are semi-aquatic and also need air to survive. They have distinct plates that shut the opening of the exoskeleton to their gills moist.

Red Claw Crab in mud

How cute are they?

The red claw crabs, like any other crabs, are not considered cute.

How do they communicate?

Red claw crabs also communicate like all other crabs through sound. They use their claws and pincers to produce flapping and drumming sounds. These crabs sense their biomes using the hair on their claws and legs to taste the sand.

How big is a red claw crab?

Red claw crabs have a carapace length of about 2 in (5 cm). The leg span is 4 in (10 cm) in length. The female is smaller than the male in size. Males also have larger claws.

How fast can a red claw crab run?

The exact speed of a red claw crab is not yet known. However, crabs can run up to 12 mph (19.3 kph).

How much does a red claw crab weigh?

The exact weight of the red claw crabs is not yet known. Crabs usually weigh around 2 lb (900 g).

What are the male and female names of the species?

There is no specific name given to the male and female of this species.

What would you call a baby red claw crab?

There is no specific name given to the baby red claw crab. They are usually referred to as larva.

What do they eat?

These semi-aquatic creatures are omnivores and accept several foods, even plants. Their diet includes brine shrimp, shrimp, leafy greens, bloodworms, fish flakes, and fish food. They are opportunistic feeders, so they often hunt on bottom-dwelling, slow-moving, or sick fish. In a take setup, you can feed the red claw crab about twice a day.

Are they poisonous?

No, these crabs are not poisonous. Most crabs are poisonous and not venomous. When they feel threatened, they might pinch you.

Would they make a good pet?

Yes, they would make a good pet. These are popularly sold as freshwater crabs. These crabs require a 10 gal (37.8 l) tank setup. A tank can have one male with two females. Even though they are small, they require a lot of space, and this crab tank size is also less compared to their territories in the wild. As they need to breathe air, perches placed above the waterline will be helpful for them. The water to land ratio must be 3:1. They will also need a filter. The optimum temperature of the water is 22-27°C. They enjoy humid surroundings. The leftover food in the tank must be removed every 1-2 days and feed fresh foods. When you keep red claw crabs in a good tank setup with a brackish environment, they will surely thrive. Also, make sure to choose tank mates with the same salinity and temperature requirements as these species. These crabs can escape, so make sure to keep the lid on all the time.

Did you know...

These crabs need to molt to grow. This molting lasts only for a few minutes, and they'll need more time for hardening their shells after molting. They will choose their hiding place till their shell hardens.

These crabs stop eating and drinking a day before molting starts, as this helps the shell to crack open with the top lifting up. They are extremely vulnerable at this stage.

Few other names of a red claw crab are Sesarma bidens and Grapsus bidens.

The exoskeleton of red claw crabs protects them from predators.

They have the ability to shed one limb in case the limb is stuck or attacked. Like the lizard's tail, it grows back.

Their red, brown, and orange colors allow them to camouflage well in their sand surroundings.

Male crabs cannot be kept together as they get aggressive over territories and might fight, which can even lead to death.

They do get out of water for air but won't stay for long because these crabs dehydrate quickly.

After molting, they feed on their own exoskeleton, which contains a lot of calcium.

It has been reported that these creatures get used to humans after a while.

People eat around 1.5 million tons of crabs per year.

The giant Japanese spider crab is the world's largest crab and can reach 13 ft (3.9 m) across.

Can red clawed crabs live with betta fish?

No, red-clawed crabs cannot live with betta fish. Betta fish is a freshwater fish and bottom feeder. These crabs will harass this fish by pinching their fins with their claws. They can generally live with fishes, and a few tank mates that can be kept with these crabs are guppies, mollies, and tetras. Also, few predators of the red claw crabs are kelp rockfish, yellow and black rockfish, sculpins, lingcod, copper rockfish, sea otters, and more. This pet is also known to clean up the tank by feeding on any sick or bottom-feeding fish. So, make sure to pick strong, big, and peaceful fish that are middle or top feeders.

Do red claw crabs sleep?

The red claw crabs are a nocturnal species. They require 10-12 hours daylight in summer and 8-10 hours in winter. There are no records available on their sleep cycle.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! For more relatable content, check out these  whirligig beetle facts and black blister beetle facts pages.

You can even occupy yourself at home by coloring on one of our free printable crab coloring pages.

Red Claw Crab Facts

What Did They Prey On?

Fish, brine shrimp, and worms

What Type of Animal were they?


Average Litter Size?

100,000 eggs

How Much Did They Weigh?


What habitat Do they Live In?

shallow rivers, aquarium, and estuaries that meet the sea

Where Do They Live?


How Long Were They?

Carapace length: 2 in (5 cm)Leg span: 4 in (10 cm)‍

How Tall Were They?








Scientific Name

Perisesarma bidens

What Do They Look Like?

Brown, orange, and red

Skin Type


What Are Their Main Threats?


What is their Conservation Status?

Not Evaluated
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Written by Arpitha Rajendra

Bachelor of Engineering specializing in Aeronautical/Aerospace Technology, Master of Business Administration specializing in Management

Arpitha Rajendra picture

Arpitha RajendraBachelor of Engineering specializing in Aeronautical/Aerospace Technology, Master of Business Administration specializing in Management

With a background in Aeronautical Engineering and practical experience in various technical areas, Arpitha is a valuable member of the Kidadl content writing team. She did her Bachelor's degree in Engineering, specializing in Aeronautical Engineering, at Nitte Meenakshi Institute of Technology in 2020. Arpitha has honed her skills through her work with leading companies in Bangalore, where she contributed to several noteworthy projects, including the development of high-performance aircraft using morphing technology and the analysis of crack propagation using Abaqus XFEM.

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