Coconut Crabs: All about the heaviest and strongest crabs

What would you think if you were face to face with a crab one meter wide and five kilograms in weight? This is the case of the coconut crabs, the heaviest ones in the world, and also  the scariest because of their spooky appearance, but as docile as tender kitten.

General Characteristics Of The Coconut Crabs

This creature responds to the scientific name Birgus latro, and belongs to the family Coenobitidae. The coconut crab is the heaviest terrestrial arthropod on the planet, and he is a sort of hermit crab who owes his name to his great fondness for coconuts. He opens these delicious fruits by employing his huge pincers ( chelae).

Thanks to this particular characteristic, he is also called «robber crab or palm thief”, while Germans call him Palmendieb.  Moreover, metal containers, knives, forks and any other shiny object are also included in the list of this rogue, whose name «latro» comes from Latin, and it means «Thief».

It is important to point out; that the sense of smell quite developed of these creatures is often related to their skills to find different food.

Size and Weight of the Coconut Crabs

These little thieves measure up to 40 cm diameter and their leg span reaches up to 1 square meter.  It is believed that this could be the size limit for a terrestrial arthropod, an aspect which changes in the case of marine specimens, since the water helps them support their weight.

As far as their weight, it ranges between 5 and 9 kilograms. It is important to point out, that there is a slight sexual dimorphism, since the males of this species are generally much larger than females.

Coconut Crabs anatomy

Anatomical Characteristics of the Coconut Crabs

As in the case of any decapod, the body of the coconut crab is divided into a central section called cephalothorax, which has ten legs, and the abdomen. This monstrous crustacean, as described by Charles Darwin when he discovered it in the Keeling Islands, has extremely strong long legs that can support up to twenty-nine (29) kilograms of weight.

The first two pair of legs possesses two very strong pincers, which he uses to peel and open the shells of the coconuts, in order to eat their content. If you have visited the beach anytime, and have also had the opportunity to eat a coconut, you know that its shell is so hard that it takes a very sharp knife to open it.

Such pincers are so powerful, that they can even lift objects, trunks or rocks of almost thirty kilograms in weight. That´s the reason why it is really easy for them to open a coconut, a fact that actually originates their names.

The next pair of legs is also very powerful, and they are employed by this crab, to climb the palm trees up to six meters in height. So, it is easy to infer that coconuts must be a delicious delicacy for this crustacean, which venture to climb to such height just to get them.

The following legs are the smallest one, and they also have clamps at their ends. However, these limbs are only used by the offspring, when they are changing or molting their carapace, to secure their shells or and to remain well protected. The adult specimens employ these legs either to walking or jump..

The fifth and last pair of limbs is very small, so they are only used by the coconut crabs to clean their breathing organs. Usually these legs are difficult to observe, especially in the youngest specimens which carry them inside their shells, which is where these organs arelocated.

The coconut crabs are not totally terrestrial, although they have adapted very well to live on land. Like in the case of other species of crabs, the newborn coconut crabs begin their lives floating at sea. After about one month of development, they find a snail shell and move in, carrying this sort of carapace in the beginning of their terrestrial lives.

They employ an organ called a gill lung to breathe, which could not be said to be a gill or a lung as such. As these gills must remain moist, the coconut crabs often submerge their legs in the water, because these extremities have a spongy tissue that absorbs water. Although they remain on the land for a long time, they also need to have contact with water, in order to maintain their balance, and to release their eggs into it in the case of females.

The coconut crabs have red eyes, while the color of their bodies ranges between blue purple, red, or even orange.

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Reproduction Method of the Coconut Crabs

The courtship of the horseshoe crabs is fast, simple and it doesn´t happen very often, unlike that of most crabs which is prolonged. Their mating takes place on earth, between the months of May and September. Both sexes engage into a fight until the male manages to turn the female on his back, to carry out the mating.

This peculiar process takes around fifteen minutes. After that, the female carries the eggs that have been fertilized under her abdomen. Once the eggs are about to hatch, she moves to the seashore, where the eggs spawn at high tide.

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The larvae of the Coconut Crabs

Once the larvae are deposited into the sea, they remain floating for twenty-eight days, during which time they develop. Then they pass to an amphibious stage and migrate toward the land, occupying the shells of the gastropods.

This is an intrinsic habit that allows the young coconut crabs to protect themselves from desiccation and their predators, since this is the most vulnerable stage of their lives. When they are between two or three years old, they measure less than two centimeters, although they leave from their shells for the first time anyway, to become a miniature specimen.

At this age they molt their exoskeleton very often, which allows them to have a continuous growth. They carry out this 30 days process in a burrow, in order to be properly protected against their predators. Then they feed on their old exoskeleton, until the new one becomes enough strong and they can leave their burrow

juvenile coconut crabs

What Do The Coconut Crabs Feed On?

Although this crab receives his name for eating coconuts from palm trees, its diet is also made up of other fruits such as fig, (including the leaves of such tree), fruits in a state of decomposition, and some other types of organic matter.

Moreover, the sea turtles and their eggs, the corpses of certain animals and the molted exoskeletons of other crabs, also comprise the diet of the coconut crabs.

As we mentioned earlier, the coconut crabs are opportunist and skillful thieves who usually steal the food of other animals. Then they take their loot to their burrows to enjoy it without danger.

When these arthropods are searching for coconuts, they climb onto the palm trees get their food. Moreover, they also employ these trees on certain occasions to shelter from the heat, and to escape from any predator that may be stalking.

As soon as the crab reaches the coconut, it falls off  and falls to the ground, where its skilled predator employs its strong pincers to perforate it and eat its contents.

How do coconuts crabs open coconuts?

He has a technique that is unique in the animal kingdom. If the fruit still has its external cover, then the crab employs its powerful pincers to remove it in strips, beginning where the fruit germinates.  This means, the three small circles or pores, which is where the Coconut is usually fixed on the palm tree.

When the crab visualizes those circles or pores, he proceeds to hit them with his pincers until he manages to pierce them. Once the coconut has been drilled, he also uses his tongs to extract the content of the fruit. When the specimen is an adult, the process is easier, and it has been demonstrated how  they can split the coconuts into several pieces.

The coconut crabs apply around 3300 newton through their pincers which is the biggest value of power in terms of proportion within the animal Kingdome. In the case of alligators, they apply around 16000 newton by employing their jaws, but there are several times bigger than the coconut crabs.

When the Birgus latro crabs live close to people, they can become true opportunists and scavengers, because in addition to stealing different kind of bright things from the sand (kitchen utensils i.e), they also steal fruits and vegetables from the crops they go through.

There have even been cases of these animals, which have scavenged in garbage cans, and attacked domestic animals. This happens only when the crabs do not have enough food, and they leave their habitat to look for it .Although none of the attacks on cats and other pets have been sustained, most people take their forecasts when coconut crabs are near their homes.

Because of the invasion and destruction of their natural habitat, these crabs have to move to other places looking for a place where they can find their food. On many occasions human beings complain about this situation, but we must remember that we are the ones who destroy or pollute their habitat.

Common Habitat of the Coconut Crabs

In general, coconut crabs like to live among the cracks of the rocks, and in burrows made in the sand, although these preferences change in some occasions depending on the places available.  They enjoy living alone, so they become aggressive with anyone who takes the risk to visit them in their hiding places.

In terms of specific location, the Indian Ocean is the place with the largest number of coconut crabs, having a huge representation in the Christmas islands, and in the Seychelles islands. The islands of Andaman and Nicobar in India, the islands of the Society that are part of French Polynesia, and the Bay of Bengal in Sri Lanka, are other common location of this specie

As far as the Pacific Ocean we can mention the Cook Islands, located between New Zealand and Hawaii, as the main habitat of these crabs in such location.

As mentioned above, these crustacean live in burrows that they dig in the sand, or in not to hard soils. They even take advantage and occupy abandoned houses.

It´s   very important for the coconut crabs to maintain the moisture of their bodies. This way they can breathe more easily. This fact makes of them nocturnal creatures who remain vegetating in their burrow during the day. However, in those places where there is a dense population of these crabs, they can also be seen during the day searching for food.

Distribution of the Coconut Crabs?

As we already know, Christmas Island is the place that has more specimens of coconut crabs. It is also to point out, that they present different tonalities of colors, depending on the specific location where they live. Blue, purple, brown and Violet, are the most common colors that can be mentioned.

The coconut crabs lose the ability to swim when they become into adults. For this reason, it is believed that these animals have to reach land when they are still at the larval stage.  However, some researchers differ from this theory, since the larval stage last only 28 days, and it takes much more than this time to get to the islands where they inhabit.

According to this theory, they must have reached land by floating on wood or some other way. Moreover, there are several islands that are located much closer for them than the Christmas Island, and they have never been seen there.

Thus, there are still a lot of things to learn about these crabs. Probably they do inhabit in other islands, or they just disappeared of such places for different reasons.

coconut crabs Christmas Island

Are coconut crabs endangered?

According to the International Union for the Conservation of Nature, there is not enough data to determine if the coconut crab is an endangered species; so they are classified as «DD«, which means data deficient.

Although these crabs are considered very important in several of the islands where they live, some person don´t think this way, and they are completely indifferent about these creatures.

The specific population varies depending on the particular island. The coastal development of some areas reduces the natural habitat of this species.  Moreover, the demographic explosion that has taken place in their environments also affects them. There are certain areas where this species is protected, but the regulations applied are not always followed, and it has been proved that where there is human presence, the population of the coconut crab decreases.

Main Predators of the Coconut Crabs

In terms of predators, the human beings are the only ones who really threaten the adult coconut crabs. However, the young specimens of this species are quite vulnerable to rats, pigs, ants, and some carnivorous species.

The coconut crabs are considered a delicacy in Southeast Asia and some Pacific Islands, and their eggs are famous because of their aphrodisiacs properties. In Japan, coconut crabs are also sold as pets, and sometimes people raise them and feed them until they can eat be eaten, as we commonly do with pigs and chickens in Western countries.

These facts promote the hunting of these crustaceans for commercial purposes, which results in the decrease of their population.

The regulations that have been created to protect this species, are focused to forbid its hunting only on certain seasons, and it has been proven they are not properly followed. Thus, its hunting and indiscriminate capture continues.

Despite the pressure exerted by various environmental organizations, for the preservation and conservation of the coconut crab, not much progress has been really made so far.

One of the main reasons relies on the unscrupulous behavior of some people, who keep destroying the wonders that Mother Nature offers. They just keep marketing the meat of this crab in the splendid art of gastronomy.  In addition, since the meat of the coconut crabs has a flavor quite similar to that of lobsters, it is commonly offered in some restaurants as such. In this way, people think they are paying for a succulent lobster, when in fact they are eating coconut crabs.

The eggs of the coconut crabs,  are usually sold at an exorbitant amount a dozen, while the fat of the abdomen also has a good number of people who like it, so that the population of this crustacean has been drastically declining, before the undaunted gaze of the people.

Despite some unconfirmed rumors, regarding the poisonous condition of this species, many people consider that it is a risk that really worth. They really consider it a delicate delicacy, especially in Japan.

Hunting Coconut Crabs

This animal is usually hunted at night, which is when he is more active, especially when there is a new moon. A flashlight is commonly employed for this task, since its light can immobilize the animal for a moment. In some occasion they are also captured during the day, attacking them in their burrows with fire, to force them out.

According to some of the inhabitants of Christmas Island, the burning of nuts is a powerful attractant of the coconut crabs, so when they want to hunt them, they resort to it to trap them and ambush them more easily.

Let´s keep learning about them

What can We Do to Protect Our Environment?

The situation that coconut crabs go through is common for many marine species, and all living beings in general. Acting with conscience and responsibility should be the first attitude we must assume.

Following, we list some easy tips that everyone should follow in order to protect our world

Reduce Energy Consumption:

Keep in mind that many of the environmental problems that we have at the moment are related to global warming. Carbon dioxide emissions from vehicles, are the main responsible of this phenomenon. Therefore reducing the use of your vehicle is a great contribution in this regard. When displacing short distances you can do it  by walking, which is also beneficial for health. In the same way you can alternate the use of your vehicle with public transport.

Make Safe, Sustainable Seafood Choices

Remember that due to the overfishing of many marine species, their populations are in constant decline. Therefore, when consuming them, choose those that are not considered to be at risk of extinction and, more important, alternate the consumption of any of them.

Recycle Plastic Containers

The plastic containers that we use on the beaches, generally end up as oceanic remains and contribute to a great extent to the destruction of such habitat. To limit their impact, simply do not throw it into the water. Recycling and reusing them is always the best option.

Travel the Ocean Responsibly

Practice responsible boating, and other recreational activities. Don´t throw anything overboard, and be aware of marine life in the waters around you. If you’re planning a cruise, do some research to find the most eco-friendly option

Provide Support to Marine Species Protection Organizations

Many organizations work hard to protect ocean habitats and marine wildlife. Find one of these organizations in your own country and consider giving financial support or volunteering for hands-on work.  If you live close to a coastal area, join a local branch or group and get involved in projects close to home.

Raise awareness among other people.

Keep in mind that not all people are aware of the environmental problems of current times. Instructing them in this respect and sharing the information we provide in this article is a way to achieve a better preservation of our world


Remember that the earth is the only home we have.

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