Blackback land crab – Detailed Guide: Care, Diet, and Breeding

Blackback land crab (Gecarcinus lateralis) – Detailed Guide Care, Diet, and Breeding

Gecarcinus lateralis, also known as the Black land crab, is a terrestrial crab known for its interesting coloration, and ease of care. These land crabs can make great pets in terrarium and paludarium setups.

Black land crab is an extremely adaptable species. These hardy crabs can be easily recommended for beginners because they do not have specific requirements for the tank set up to thrive.

Keep reading for more information about the Black land crabs and how to care for them in your home terrarium or paludarium.

Quick Notes about Blackback Land Crab

Name Black land crab
Other Names
Bermuda land crab, Red land crab, or Purple land crab
Scientific Name Gecarcinus lateralis
Tank size (minimum) 15 gallons (~60 liters)
Type Terrestrial
Keeping Easy
Breeding Very Difficult 
Size (carapace) up to 4 inches (10 cm)
Optimal Temperature 73 – 82°F (23 – 28°C)
Water type Does not require
Moisture 70 – 90%
Substrate more than 6 inches (15 cm)
Diet Mostly herbivore/omnivore
Temperament Aggressive  
Life span up to 8 years
Color Form Purple, black, and orange

Origins, Natural Habitat of Blackback Land Crab

Black land crabs inhabit tropical and subtropical coastal areas.

This species is widely distributed along the Atlantic Ocean from Florida to Brazil, including Mexico, the Caribbean Islands, and French Guyana, and along the Pacific Ocean, it is distributed from Mexico to Colombia, Venezuela, and Peru. Black land crabs have also been reported from the Gulf Coast of Texas.

In their natural habitat, they are mostly found on the upper beaches or in dry but humid sandy scrublands and grasslands inland from the beaches.

Occasionally, Black land crabs can be found even in heavily wooded coastal areas where they play a significant role in the structuring and functioning of the coastal ecosystem by processing organic litter, recycling nutrients, and aerating the soil.

Description of Blackback Land Crab

Blackback land crab (Gecarcinus lateralis) – Detailed Guide Care, Diet, and Breeding on the sandGecarcinus lateralis is not a small species. Fully grown crabs can reach up to 4 inches (10 cm) long, with a leg span up to 6 inches (about 15 cm).

Note: In the aquariums, the average size (shell width) of the adult crabs is often near 2 – 2.5 inches (5 – 6 cm) long and 4 – 5 inches (10 – 12 cm) across the leg span and achieve a fresh mass of approximately 1.5 oz (45 g).

So, it will be a good idea to give it extra space in your tank in case it grows a little larger than expected.

Like all crabs, Black land crabs have a total of 10 long bright orange legs including 2 pinchers which they use for eating. The claws are relatively large but in adults, they can be slightly or evidently different in size and robustness.

Coloration:

  • The dorsal surface of the carapace ranges from deep purple to almost black color (hence the common name, “Blackback”).
  • The lateral margins is orange and posteriorly light cream.
  • Claws are orange (sometimes with a purple tint).

All variations in color are usually limited to a relatively small, lightly colored area on the posterior part of the carapace.

Difference between Blackback Land Crab, Rainbow Crab, and Halloween Moon Crab

Unfortunately, these three species can be easily confused with each other because they are quite similar in color and appearance, especially, when they are young. Even scientists have some problems with that.

For example, taxonomically, several researchers have tried to differentiate Gecarcinus lateralis (Black land crab) and Gecarcinus quadratus (Halloween Moon crab). At some point, these two species have even occasionally been considered synonyms.

Nonetheless, nowadays they are considered different species. The estimated time of divergence between them ranged between 2.3 to 4.3 million years.

Misidentification is one of the main reasons, why people cannot provide proper care for these crabs.

  Rainbow Crab (Cardisoma Armatum) Blackback Land Crab (Grecarcinus Lateralis) Halloween Moon Crabs

Gecarcinus Quadratus

Vivarium type Paludarium Terrarium Terrarium
Avarage size of the carapace Up to 4 inches 2 – 2,5 inches 2 – 2,5 inches
Color form Purple-blue carapace.
Whitish claws.No dots on the back.White to grey eyestalks.
Mostly reddish with a dark spot on the back.
Usually do not have dots on the back. Dark eyestalks.
Mostly orange legs with a fully dark carapace.

2 white and orange dots on the back and near eyes.

Dark eyestalks.

Temperament Very aggressive Aggressive Aggressive

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Lifespan of Blackback Land Crab

Currently, there is no data available on the maximum lifespan for Black land crabs in the wild.

However, in captivity, their life expectancy depends on a number of factors such as disease, poor living conditions, and shipment stress.

if appropriately cared for, Black land crabs can live up to 8 years. However, the average lifespan is around 4 – 6 years.

Behavior of Blackback Land Crab

Gecarcinus lateralis is a fully terrestrial species. In the wild, they can be found a few kilometers away from the Oceans.

Black land crabs are excellent climbers. According to some observations, they often being found 2 to 6 feet up a tree.

These crabs are also natural diggers. In nature, they burrow holes 6 – 20 inches (15 – 50 cm) deep.

They are solitary and also pretty shy animals. Black land crabs are usually not involved with other members of their species. Therefore, overcrowding will definitely not end well.

Generally, they are nocturnal and become active almost exclusively at twilight and in darkness. However, there are some exceptions, for example, it was observed that heavy rain showers greatly enhance the activity of land crabs, even when the light is relatively strong.

Note: Black land crabs can be seen outside of their burrows during hours of daylight more often if humidity and temperature are high and there are lots of protective cover for a quick retreat. Nonetheless, such behavior is unusual in this species.

Features:

  • Social: No
  • Active: No
  • Peaceful: No
  • Burrowers: Yes 

Blackback Land Crab and Strange Sounds

Among the important characteristics of genus Gecarcinus is that they have the stridulatory apparatus which is used to produce sounds when these crabs are disturbed.

The sound is produced by the friction of the claws against the carapace.

Note: In scientific terms, when oblique rows of rugosities on the subhepatic region are rubbed against the tuberculated internal margin of the merus of the cheliped in Gecarcinus quadratus, or against a longitudinal tuberculated ridge on the internal surface of the palm of the major cheliped in Gecarcinus lateralis.

There is a theory that the sound can have a startling effect that could temporarily disorient an attacking predator or if the sound were produced in close temporal proximity with pain inflicted by claws the predator might learn to associate the sound with the pain and exhibit avoidance behavior in the future.

Feeding Blackback Land Crab

Like most crab species, Black land crabs are classified as opportunistic omnivores (because they have adapted to eating both animal and plant material) with a primarily vegetarian diet.

At the same time, according to the study, the natural plant diet is a growth-limiting factor for this species. Multiple observations indicated that these crabs will also show a strong preference for high nitrogen foods such as carrion and animal feces and will congregate around these food items in large numbers.

Therefore, despite being primarily vegetarians, Black land crabs require protein food as well. Supplementation of the diet with protein-rich food (about 10 – 15% of the diet) will reduce cannibalism in this species.

Foods Black land crabs will enjoy (examples with links to check the price on Amazon), for example:

Leaves (for example, Almond leaves, dead beech, oak leaves, etc.) should always be on the menu, as they feed on these and require the detritus from the leaves. 

Important: Black land crabs show a strong effect of the moisture content of the food. They can eat anywhere from 3 to 6 times more green and decaying food compared to dry food. This is how they obtain much of the necessary liquid.

Features:

  • Diet Type: Mostly herbivore / omnivore
  • Food Preference: Leaves and plants
  • Feeding Frequency: 3 – 4 times a week

How often should We Change the Food?

Leave their food for anywhere between 12 and 24 hours before removing it to prevent moles.

As Black land crabs exhibit nocturnal foraging behavior, the food should be given in the evening. 

How often should We Change the Menu?

To keep Black land crabs healthy, it is recommended to change their diet at least every week or two. Do not give them the same food all the time.

Do Black land crabs Need Calcium?

Yes. They do.

Calcium (Ca) plays a vital role for crustaceans. It is used in the new exoskeleton to harden it after the old exoskeleton has been shed during the post-molt period.

Therefore it is absolutely crucial to supplement their diet with eggshells, cuttlebone, etc. Also, make sure they get enough calcium (for the exoskeleton) by regularly feeding specialized invert foods. 

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Keeping and Housing Blackback Land Crab

Black land crabs are one of the easiest pets to care for because they adapt well to life in captivity and can stay pretty healthy in most situations.

Nonetheless, owning any pet carries significant responsibility and obligation to address their core needs! 

Here are some care guidelines to help you out:

Tank Size (Enclosure):

According to the study, Gecarcinus lateralis are ubiquitous in the tropical semi-deciduous forest, with a density of 1 crab per 0.5 to 1 m2 (equal to 5 – 10 square feet).

Therefore, the minimum recommended tank size for one Black land crabs is a 15-gallon (60-liter) tank. Nonetheless, as we can see, even this size is not enough for ideal conditions.

Note: Black land crabs are great escape artists. So, a tight-fitting lid is essential.

Lighting:

No special requirements. Black land crabs are nocturnal animals. Thus, you may not even need one.

If you have plants, lighting should be adapted to their needs. However, keep in mind that this species is not plant safe as they are mostly herbivorous. So, they will eat, cut, and uproot everything that is possible in their tank.

Temperature:

The optimal temperature range for Black land crabs is 73 – 82°F (23 – 28°C), but it does not mean that they are very sensitive.

On the contrary, Black land crabs are very hardy animals and can tolerate a huge range of temperatures. However, it will affect their behavior.

For example, if the air temperature drops below 64°F (18°C) their activity lowers significantly. If the temperature reaches 45°F (7°C), they stay underground within their burrow and may even seal the entrance.

If you decide to use a heating pad, it should not cover more than one-third of the tank. In these cases, the crab can move from warmer to colder places anytime it wants.

Another alternative is to place it on the back outside wall of your glass tank. So, in case of malfunctioning, it will not roast the animal.

I also definitely recommend a thermostat. It will protect your Black land crabs from overheating or getting too cold.
Tip: You can always use ceramic or heat bulbs as a heat source. Depending on the setup, it can be even preferable.

One of the most popular heaters – Zoo Med Repti Therm Under Tank Heater (check the price on Amazon).

Humidity:

The tank should be tropical in nature with a relative humidity between 70-90%. Humid air lets them breathe properly.

According to the study, Gecarcinus lateralis tolerates, on average, 21% body water loss, with some individuals losing over 30% of their body water before they succumb.

Because of this, they developed mechanisms to avoid desiccation by constructing burrows and reducing their metabolism during periods of drying.

Some ways to provide and keep humidity:

  • keep the substrate moist,
  • use a glass top to reduce evaporation,
  • provide water sources for your crabs.
  • provide water for your crabs, and use a glass top. If your humidity levels stay too high or too low, it can be remedied by adding more moisture, less ventilation, or by adding more ventilation.

Be careful and avoid over humidifying as a saturated substrate can breed infection. This is normally a trial and error process, so expect it to take some adjusting to get it perfect.

Examples – Humidity and Thermometer (links to Amazon):

Water Bowls:

In their natural habitat, Black land crabs live in burrows well above tide level, and their only contacts with water are during the spawning season and rainy season. Generally, they absorb water from food, dew, and the substrate.

Therefore, these crabs have the capacity to exist for an indefinite period without access to water. At the same time, it was noted that Black land crabs became more active during the rain.

Nonetheless, even though Black land crabs are adapted to terrestrial conditions and do not require an aquatic environment I would still recommend using small water bowls in their setups.

Blackback land crab (Gecarcinus lateralis) – Detailed Guide Care, Diet, and Breeding in waterThe water only needs to be a few inches deep to completely submerge your crab.

Do not worry, these crabs will not drown right away. Compared to most other crustaceans, their blood also has a higher oxygen-carrying capacity. It allows them to stay in the water for a long time, although, this is very unusual for this species.

Interesting fact: According to the study, Black land crab female was collected in 0.3 m of water in Laguna Madre about 185 m offshore from South Padre Island, Texas.

Laboratory experiments have shown that before drowning, Gecarcinus lateralis can remain submerged:

  • for 12 to 27 hours in seawater (salinity: about 30 %) for 12 to 27 hours,
  • 5 to 9 hours in tap water.

Tip: Provide a variety of surfaces for them to get out of the water. For example, place some rocks or driftwood in the water to climb onto.

Substrate:

Black land crab need a combination of moist sand or mud into which they can burrow.

In order to dig underground and form a cave, the substrate should always be kept moist enough. It means that it should hold its shape when you squeeze it. However, not so wet that it drips or pools water.

To get “sandcastle consistency”, a mixture of cocofiber and sand will be the best option for Black land crab setups.

Tip: There is a simple trick to test the consistency. Take a pencil and stick it all the way down and pull back up. If the tunnel doesn’t collapse, your substrate is good enough.

The substrate may also require maintenance such as spraying with fresh dechlorinated water on a regular basis in order to keep it moist enough since the moisture in it will evaporate over time.

Important: Do not ever use saltwater to maintain moisture as salt does not evaporate and can lead to a harmful salt build-up.

How Deep should be the Substrate in Black land crab Setup?

The deeper the better.

In the wild, these crabs make burrows up to 16 – 24 inches (40 – 60 cm) deep. So, I’d start with at least 10 cm (4 inches) deep.

Substrate options (check the price to Amazon): 

Decorations and Hiding Spots:

Black land crabs need a lot of hiding places to be happy. It can be all types of leaves, rocks, wood, plants, PVC pipes, and other decorations to enrich the environment in your tank. It is very important to minimize stress to your crabs by giving them a lot of places to hide.

This is also critical for the molting process!

Molting Blackback Land Crab

In order to grow, the Black land crab will shed its exoskeleton in a process called molting. It also allows them to restore lost limbs.

In nature, this species usually sheds its old shell and hardens its new one within the burrow to increase its chances of surviving the vulnerable soft-shell stage.

There are 4 molting stages:

  1. Inter-molt stage,
  2. Pre-molt stage,
  3. Molt stage,
  4. Post-molt stage.

Important:

Molting is extremely stressful process for them, so you need to follow these guidelines:

  • NEVER disturb your Black land crab when they are Give it time.
  • Keep giving calcium-rich foods and food that has minerals. It will allow the crab to harden the shell faster.
  • Don’t remove old exoskeletons from the tank because there are lots of nutrients left inside it. The black land crab will eat it later.
  • Just keep putting new food in the tank even if they’ve been missing for days at a time
  • Don’t panic if they do not come up after molting for a few days. They hide during molting.

For more information, read my article “Crabs and Molting Process”.

Some Important Rules Regarding Care and Handling:

  • Black land crab are not pets you can play with. Do not take them out just because you want to.
  • Black land crabs should never be lifted up by their legs or claws! You need to be extra careful when capturing crabs as legs and claws can easily be detached by autotomy. Do not try to pull them from the burrow, it is almost impossible to do that without harming them.
  • The proper method of grabbing them is from behind and grasping the rear of the carapace.
  • Do not leave uneaten food for too long. It will cause smell and bacteria in their enclosure. Keep in mind, Black land crabs can store uneaten food in their burrows.
  • Provide as many hiding places as you can!
  • Keep the warm temperature and high humidity.
  • The substrate should be based on coconut fiber, soil, and peat to give them a homely feeling.
  • Make sure the lid of the tank is closed tightly so that they cannot escape it.

As we can see, with the proper steps and precautions, anybody can care for Black land crab pretty easily.

Related article:

Sexing Blackback Land Crab

It is relatively easy to tell whether they are male or female.

  1. Size. Males are a little bit bigger than females and have larger claws. In addition, the claws are often not even in male Black land crab
  2. Abdomens. Abdomen subtriangular and narrow in males, semi-circular and broad in females with 7 articulated somites in both sexes

Mating Fact:

  1. There is no description of complex courtship behavior in Black land crab.
  2. Unlike many other crab species, females usually stay in an upper position whereas males are passive simply clasping her with his walking legs. Toward the end of mating, the male may place his claws on the carapace of the female.
  3. Males can be smaller when females.
  4. Females do not need to molt before mating. They stay in the hard-shelled condition.
  5. On average, the copulation lasts around 15 minutes.
  6. Two out of three times they prefer do that inside the burrow.

The typical size at maturity of this species is about 8 – 10 mm (~0.3 – 0.4 inches). 

Breeding Blackback Land Crab

Unfortunately, it is close to impossible to breed Black land crab in captivity. Currently, the pet industry completely depends on wild-caught species. 

This is what I found in scientific literature:

  1. Females reach maturity at 2 inches (3 cm) carapace width.
  2. After mating, females usually stay in burrow while carrying their developing eggs for the 15 to 16 days.
  3. Black land crabs migrate to the ocean to release eggs that hatch into planktonic marine larvae. It is synchronized with full moon nights.
  4. Each female may produce from 20,000 to 100,000 according to the size of crab. However, only a small fraction of them eventually metamorphose and crawl back onto land.
  5. An ovigerous female may eat her own eggs, if the eggs are damaged or, for any reason, are not developing.
  6. So far, no one has yet studied the complete larval development of Gecarcinus laterali
  7. Their larvae live in the sea and return to brackish water to develop into megalops and young crabs.
  8. The smallest crabs that were collected measured 1 inches (2.65 mm) carapace width

Blackback Land Crab and Suitable Tankmates

Before putting any new tank mate in with your Black land crab, you should take some things into consideration:

  • Although this species is not extremely aggressive, these crabs are still not peaceful and inoffensive. Black land crabs are not social. It can be risky to house multiple animals in the same tank as well.
  • They are territorial (especially males). Males are extremely likely to fight when housed together.
  • Do not make them hungry. It will increase their aggression and canibalisation.
  • Do not keep them with Hermit crabs. Black land crabs are stronger and can bully hermit crabs. In addition, Black land crabs dig a lot. So, it can be very dangerous to any underground molting

Ideally, Black land crab should be placed in a tank alone or with other Black land crab of another sex if the size of the enclosure allows it.

In Conclusion

Black land crabs (Gecarcinus lateralis) are fist sized, beautiful terrestrial crabs adorned with bright orange legs and claws with a splash of dark on their backs.  

These crabs have a lot of character, personality, and can be a great addition to your home tank. They will certainly keep you occupied.

Related Articles:

  1. 7 Freshwater Crabs For The Tank.
  2. Difference between Aquarium, Terrarium, Riparium, and Paludarium?
  3. How to Set up Paludarium

References:

  1. Bliss, D. E. 1962. Neuroendocrine control of locomotor activity in the land crab Gecarcinus lateralis. Soc. Endocrinol. Mem., no. 12, Neurosecretion, pp. 391-410
  2. Bliss, D. E. andj. R. Boyer. 1964. Environmental regulation of growth in the decapod crustacean Gecarcinus lateralis. Gen. Comp. Endocrinol. 4:15-41
  3. Cabrera, J. A. 1966. Contribuciones carcinologicas I. El primer estadio zoea en Gecarcinus lateralis (Freminville) (Brachyura Gecarcinidae) procedente de Veracruz, Mexico.
  4. From Sea to Tree: Saga of a Land Crab. AMER. ZOOL., 19:385-410(1979)
  5. DENSITY and Population STRUCTURe of the red land crab Gecarcinus lateralis IN a tropical semi-deciduous forest in VERACRUZ, MEXICO. INCI v.28 n.6 Caracas jun. 2003
  6. Food Quality and Cannibalism in the Red Land Crab, Gecarcinus lateralis. Physiological Zoology 57, No. 3 (May – Jun., 1984), pp. 318-324 
  7. C. Taylor & P. Spencer Davies (1981). “Respiration in the land crab, Gecarcinus lateralis”(PDF). Journal of Experimental Biology. 93 (1): 197–208.
  8. Burrowing Habits, Habitat Selections, and Behaviors of Four Common Dominican Land Crabs; Guinotia dentata, Gecarcinus lateralis, Gecarcinus ruricola, and Cardisoma guanhumi. Dominica Tropical Research Biology 2009
  9. A morphological, phylogenetic and phylogeographic reappraisal of the land crabs Gecarcinus quadratus De Saussure, 1853, and G. lateralis Fréminville in Guérin, 1832 (Decapoda: Gecarcinidae). Are they different species? Zootaxa 5048 (2): 215–236. 2021

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