The blackback land crab is an aggressive and beautiful addition to your hobby. Compared to other crab species, this crab has several unique behaviors and needs that you might not be aware of.
It is a species that can adapt fairly well to a variety of environments and is relatively easy to care for in captivity, though there are a few things to keep in mind. Here I’ll talk everything you need to learn about Gecarcinus lateralis aka blackback land crab.
Quick overview of Gecarcinus lateralis
| Names | Bermuda land crab, red land crab, and blackback land crab |
| Scientific name | Gecarcinus lateralis |
| Care level | Easy |
| Size | Up to 4.5 inches (carapace)Up to 5-6 inches (with legs) |
| Lifespan | Up to 5 years in captivity |
| Color | Black, Orange, Red, and Purple |
| Breeding | Difficult |
| Optimal temperature | 73 – 82°F (23 – 28°C) |
| Temperament | Agressive |
| Diet | Herbivore |
| Sleeping nature | Nocturnal |
Blackback land crab facts
Distribution and habitat
Gecarcinus lateralis lives close to the sea but above tide level in tropical semi-deciduous forests, mangroves, dry zones of sandy beaches and nearby hills. It is spread throughout the Atlantic coast of Mexico, the Caribbean islands, and parts of Central America.
Blackback land crab is widely popular for it’s delicious meat in the West Indies.
A unique ion adaptation
As they live in upland areas, they have limited access to salt, so they developed a way to conserve ions (salts) very effectively, keeping high levels of these ions in their blood even though their urine has the same concentration as their blood.
The blackback land crabs conserve ions by reprocessing their urine, significantly reducing ion loss even in salt-limited environments. This adaptation, similar to that of ghost crabs, helps them retain valuable salts, turning their urine into a concentrated resource, crucial for survival in freshwater surroundings. 2
Breeding
Female blackback land crabs leave their safe burrows to take their eggs to the ocean and release larvae. During this time, they face dangers like predators, changes in salinity, and waves. They do certain things to protect themselves and the eggs, such as –
- Start their journey before they are ready to release eggs (to avoid early release due to rain.)
- Move straight to the shore to reduce travel time.
- Release eggs with other females.
- Avoid releasing eggs in standing water (which could be too salty or not salty enough).
Gecarcinus lateralis goes through six stages or maybe five, as a larva (zoeal stages) and it takes one more stage before becoming a young crab (the megalopal stage). According to research, it takes at least 29 days for the species to develop from the first zoeal stage to the young crab stage.
Appearance
They have a large black marking, which covers most of the carapace area, and the claws and legs are red to orange.
The shape of the male’s abdomen stays the same regardless of their size and females often have a larger sixth segment of their abdomen compared to males. Their gills are always moist (to breathe air) and are reduced in size to uptake salt and water.
Behavior
Crabs mostly stay in burrows and forage immediately after rainfall. In their natural habitat, they significantly accelerate litter disappearance during the wet season. They engage in fights for things like claiming territory in a dense area. The common fight between two males always ends brutally, as the weaker one has to lose claws and several legs. But no worries; they will grow new limbs after molting.
They use their claws to help walk.
A comparison study shows that the burrow of the blackback land crab is more varied with different entrances but simpler and less deep compared to the burrow of the ghost crab.
Gecarcinus lateralis burrows:
- Diameter: 32–58 mm
- Depth: 8–47 cm
- Length: 19–103 cm
- Shaft inclination: 18°–47° (mean: 28.9°)
Molting
The growth process of the red land crab depends a lot on its environment. When they get conditions like darkness, a moderate temperature and being surrounded by no other animals, they shed their old shell and grow a new one, as these conditions increase the chance of surviving after shedding.
On the other hand, they tend to slow down or stop their growth if they get light, a high temperature, and the presence of other crabs, as these conditions reduce their chances of surviving during shell shedding. Another thing that hinders their growth process is dry sand because it prevents the crab from taking in the water needed for the growth phase.1
Generally, blackback land crabs molt once a year but if they are brutally injured, they speed up the process in two months. The soft and vulnerable shell needs two to three weeks to turn into a hard shell after molting.
Blackback land crab care
Tank setup
Tank size
The blackback land crab will need a lot of space, as they are not social, even with the same species. An overcrowded tank will make them more aggressive, leading to territorial disputes.
Take a minimum 20 gallon tank for one crab or 30 gallons for two crabs; go above 30 gallons if possible and increase the size accordingly with the number of crabs. You can’t keep other animals with them; the tankmates you can best prefer are the opposite sex of blackback crabs.
Substrate
They are fully terrestrial crabs; they barely go to the sea, like when releasing the eggs. So they’ll need a proper substrate that mimics their natural habitat best. The substrate should be able to hold moisture for a long time, have enough aeration and hold its shape.
To make the substrate, take beach sand, peat, and leaf litter. You can find all of them on Amazon. Now tear off some of the leaf litters and mix them with the beach sand and peat moss. Now your substrate is ready to enter the tank.
A deeper substrate will be better, I prefer a substrate that is at least 8 to 10 inches deep, which will help their burrowing.
Decoration
Blackback land crabs are great at climbing. So you’ll have to provide climbing materials such as driftwoods, spiderwood, and stones. Make some hiding places with moss caves, wood caves or stone caves.
Water, temperature, humidity and light requirements
You can create a section for saltwater, which will be 10% of the whole area, like a paludarium. Also, provide a freshwater bowl.
The temperature should be between 73 and 82°F (23 and 28°C), with the humidity between 70% and 90%. Use related equipment like a thermometer, hygrometer and humidifier.
Set the light mimicking natural day and night—12 hours of day and 12 hours of night—at least if you can’t regularly adjust it with sunlight.
Blackback land crab diet (Gecarcinus lateralis)
They are herbivorous, depending on leaves and plant matters. In captivity, you can offer them fresh vegetables and fruits. They may keep the food to rot and then eat, which is normal crab instinct. I prefer giving half boiled vegetables like carrots and spinach.
Provide calcium rich foods such as cuttlebone to help your blackback land crab recover from molting and grow a strong exoskeleton. They eat worms if they like, so technically, blackback land crabs are not fully herbivores. Try feeding them fish flakes and pellets, as well as brine shrimp, small fish, insects, bloodworms and algae.
To avoid ruining the environment, do not leave rotting food in the tank for an extended period of time.
Blackback land crabs may become cannibals as they lack enough nutrients, but adding high-nutrient foods like soybeans reduces cannibalism among adults.
