The coconut crab is one of the largest terrestrial arthropods inferred by the name robber crab or the palm thief. 

The crucial habitat of the coconut crab entails islands across the Indian ocean, southwest Pacific Ocean, mainland Australia and much more. 

Coconut Crab belongs to the class Crustacea. The mating period of the coconut crabs ranges from May to September and basically between June and late August. 

It exists in the habitat, which is more likely to be the coconut palm. Considering the present context, it has been undergoing threats as the cause of anthropogenic induced interventions, such as demanding for its flesh. The trade of its flesh is increasing more in several parts of the world. 

The International Union for Conservation of Nature (IUCN) had enlisted the coconut crabs under the category “data deficit”, but now it is listed as “vulnerable”.

Plenty of fascinating facts regarding the coconut crabs have been identified so far, as mentioned below with a brief description.

1. Scavenging

Scavenger Hunt
Scavenger Hunt | Image Credit – Round glass sustain

Generally, the coconut crabs are the scavengers that do consume the fruit. It’s astounding to depict that the coconut crabs even feed on the shells of the other crabs

The primary cause of providing the other crabs’ shells is to ingest the calcium for their astonishing growth and development. 

Since the coconut crab gets calcium from the other crab’s shells, the phenomenon is usually common in them. 

The nocturnal land crab feeds primarily on protein-based items, dead and decaying matter, rats, and many more.

They love to feed the bones. The coconut crabs pick, clean up and keep them in their nests.

2. Piercing effects

Since it is found in the areas where the coconut grows, it has some relation with the coconut trees. 

It might be surprising to know that they use massive piercers to crack open the coconuts. 

Since the coconut crack seems very difficult to open using their pincers, a giant coconut crab could exert the force possessing 3,300 Newton

They can lift the materials as heavy as 61 pounds using their strength and sharp claws.

They can even drop the coconut from the trees and pierce the coconut husk before opening the seeds. 

Typically, this is a unique characteristic of the coconut crabs, rare in other terrestrial animals.

3. Red or blue color shells

Red and blue shells of coconut crab
Red and blue shells of coconut crab | Image Credit – Rawpixel

Ranging from the bright red to blue color, the scientists are still confused about what has made such colors in the shells of the coconut crabs. 

The shell color of the coconut crabs does not depend on the size, sex, or piercing force. 

4. Reason for disappearing the Amelia Earhart’s body forever

Amelia Earhart, 2nd from the right
Amelia Earhart, 2nd from the right | Image Credit – Picryl

Nikumaroro Island has a massive abundance of coconut crabs. On the Nikumaroro Island of the Central Pacific Ocean, the airplane crashed. 

The International Group for Historic Aircraft Recovery hypothesized that in the massive airplane crash, the famous pioneer aviator Amelia Earhart, the first woman to fly solo across the Atlantic Ocean worldwide, died in 1937.

She had made an emergency landing on this Island. The investigation team could not get her body forever, though she died eventually. There was a massive investigation considering this case.

It is even today believed that the massive coconut crabs dragged away the body since the Island belongs to their habitat. 

Though there is no proof that the coconut crabs were eating the aviator, her body’s disappearance and her flesh detection in the coconut crab habitat have supposed the massive coconut crab might have done something to her body.

They took away the dead body of the aviator, and even to this day, it’s unknown of the cause behind this critical and rare case.

5. Enormous growth

Giant coconut crab | Video Credit – YBS Youngbloods

Until they find the perfect shell for them, they continue feeding. They move from one cover to another throughout the year, and once they succeed in their mobility, they act as a giant, strong creature and largest arthropod all across the globe. 

Since it feeds on the other shells by recalcification, the outside of the coconut crab goes on hardening, and later on, it is converted into an enormous animal. This process continues throughout the early stage of their life.

6. Grouchy in nature

They deeply borrow into the cooler and below the tree’s roots to avoid the sun. The very uniqueness of the coconut crab is it prevents the presence of crabs of their kind. 

Since there is competition between the coconut crabs, their defending the territory looks pretty petrified. 

They present their large claws to reflect their presence and show a warning that there should not be any other crabs around them during their visit.

7. Well sea adaptation

This Crab Can’t Swim, But Has To Lay Its Eggs In The Sea | Image Credit – BBC Earth

The coconut crab is very adapted to the land, and in the water, it has outstanding characteristics to drown for an extended period. Aimed to fulfill the salt balance in its body, it sometimes drinks the seawater. 

To obtain the salt, the females, after releasing the fertilized eggs, go back to the sea again. They wait for a long time to fertilize their eggs and wait for it to hatch. 

Once the female gets ready to release the fertilized eggs, it goes to the sea. From the sea, the females enrich the salt content as per their requirements. 

Since it is crucial to achieve the salt for developing their body, returning the female coconut crab to the sea is common.

8. Human poisoning upon the consumption of the coconut crabs

Sea Mangos
Sea Mangos | Image Credit – Pxfuel

Naturally, the flesh of the coconut is not poisonous. Due to the coconut crabs diet, the meat seems to be poisoned upon consuming some food sources. 

For instance, a coastal tree named the sea mango is very poisonous. When the coconut crab feeds it, the whole body gets poisoned.

In the other sense, humans are very habituated with several dialects of the coconut crabs. 

Once humans consume the coconut crabs fed on the sea mango, they are poisoned by eating them.

9. Sense of smell

Generally, the coconut crabs possess shortened antennae intending to detect the smell in the air. 

The most interesting fact about the coconut crab is that it can smell over large distances

They could smell anything. Thus, it will be easier for them to know about the predator’s presence in its habitat. 

In the brain of the coconut crab, the olfactory system is well established; thus, it can smell the rotten meat, coconuts, and other food resources in its habitat and nearby surroundings.

They mostly hunt in the night. The forage of the coconut crab entails fruits, nuts, and much more. 

It has been revealed that the coconut crab smell is dedicated to 40 % of the crab’s brain

Mostly they prefer to live in the land but possess a perfect sense of smell. Large brain part is utilized upon detecting the odors.

10. Falling from the trees

Coconut crabs climbing a tree
Coconut crabs climbing a tree | Image Credit – Wikimedia Commons

One of the fascinating facts concerning the coconut crab is climbing the trees. It could climb the trees up to 33 feet high, which seems shocking to lament. 

It can grab the coconut once the husk is removed and bring back the nut from the top part of the trees. 

Apart from these, if the tree is no longer (15 feet) in height, it would free fall from the top position once the coconut husk is removed.

For scrapping the coconut, it may take hours to days for the coconut crabs, and once the husk is removed.

Some scientists are unclear on whether the coconut crabs have shaken the coconut tree loosely or taken the shelter only for their existence.

11. Consuming coconuts, of course

Coconut crab-eating coconut | Video Credit – Phone Booth

The curved legs and the inward grip of the coconut crabs have consistently assisted the coconut crabs in climbing the trees. 

They utilize their strong claws to crack the coconuts and easily rip the coconut parts upon their need. 

Since they primarily reside in the coconut abundance surroundings, coconut is the primary diet of the coconut crab; thus inferred the name as the coconut crabs.

12. Inferred by the name ‘Robber crabs’

To note that they possess a kind of thieving skills. In 1906, an English naturalist Henry N. Ridley mentioned the habit of the coconut crabs, which he visualized stealing the accessories such as bottles and the bots from his tent. 

Later on, another researcher supported this finding who envisioned coconut crabs hiding whiskey bottles behind it.

Though it seems like a supposing fact, the scientists believe such activities are the reason for the coconut crab’s sensitive scent organs. 

Thus, in such circumstances, the name of the ‘robber crabs’ was stressed to the coconut crabs. 

13. Long surviving period

Coconut Crab: Your Worst Nightmare | Video Credit – Animalogic

From the sense of sexuality, the coconut crab matured at nearly five years old. Once they reach the copulation phase, their body growth goes on decreasing. 

The offspring of the coconut crabs face multiple threats from their predators since they are young. 

It is supposed that they survive from 40 to 60 years, and because of their slow growth mechanism after the maturity stage, predators could overharvest the coconut crabs with ease. 

The predators easily detect and attack them. They seem strong enough during the adult stage but are weak in maturity.

14. Carrying developing young under the abdomen

Every mother cares about their children presenting soundly. The same is in the case of coconut crabs. 

After mating by the coconut crabs, females stick their eggs to the particular appendage they possess and carry under their abdomens.

The young ones develop inside the eggs, and the mother sticks the young near the sea’s edge. 

The crucial cause of sticking the young by the mother to the sea edge is moistening the eggs. 

When the young become ready to hatch, sticking to the edge of the sea is ended. And the floating babies must seek after themselves. 

Without practical love and affection, it would not be easy to survive by floating babies. Unfortunately, few of the total could only stay in returning to the land. 

It relies upon the climatic condition such as temperature, pressure, humidity content, and other factors such as maternal care. 

15. Unique respiration process

For breathing, the coconut crabs use a particular type of organ known as a branchiostegal lung. 

The branchiostegal lung assists hugely in adaptations to its habitat. The most interesting fact that the coconut crabs possess is cleaning the breathing organs by the legs pair and moistening them with the water. 

For this, water is very crucial to function these activities and stroke the wet legs in the spongy tissues. 

Not every crustacean possesses the branchiostegal lung and is considered unique.

16. Not Social at all

Two coconut crabs fighting
Two coconut crabs fighting | Image Credit – Wikimedia Commons

These crabs could be anti-social in nature. Mostly, they block the entrance burrow. 

The principal intention of blocking the burrowing by the coconut crabs is to take out the unwanted visitors to his home. It doesn’t prefer to socialize with other species since they are solitary. 

It occupies its territory and does not allow others to enter its habitat (burrow). 

This trait is considered unique. It defends with the other species who are near to its habitat.  

The coconut crabs always choose to live alone, enjoying themselves in the natural surroundings or the habitat. 

To harden their exoskeleton may take them either days or weeks. They mostly remain in their burros/homes to avoid the unwanted challenges that might have occurred to them. 

In such circumstances, they could feed in their shed shell or discard it if not necessary.

17. Drowning

After the mother releases their eggs on the ocean, coconut crabs hatch with the time the eggs mature. They do pass the larval stage. 

The adult coconut crabs spend their entire life within the land. Although the eggs of the coconut crabs are stuck to the sea edge in the adult stage at the initial phase, they are allowed to remain only in the land.

If they return to the water at the adult stage for an extended period, they get drowned away in the water. 

Their body mechanism is developed so that once they reach the adult stage, their swimming ability remains very slow and thus, results in the water drowning. 

During their small age, they seem perfect in swimming in support of their mothers. 

But the adult stage always forces them to slow swimming and unfortunately drowned them when they could not swim.

18. Island invaders

Species invasion is not a new issue in species management and conservation over the years. 

The pigs, and the dogs have encroached on the coconut crab’s territory.  Most troublingly, it could wipe away the habitat of the coconut crabs for a prolonged period. 

The larvae of the coconut crab, as born in the ocean, were supposed to have drifted to Hawaii. 

Still, the coconut crabs’ concern arises on how they would have acted as an invasion, shifting the aquatic larva to Hawaii. 

It’s worrisome to stress that if the coconut is not enough for them to feed upon, it may increase the risk of targeting their versatile diet to the native animals of nature.

18. Largest land crustacean

Japanese spider crab
Japanese spider crab | Image Credit – Flickr

Although the Japanese spider crab is considered a giant crustacean, it is limited to only marine dwellings. 

The coconut crab is considered the largest crustacean dwelling in the land all across the globe. It possesses five pounds in weight and a leg span of 36 inches.

Conclusion

The coconut crab does possess several fascinating behaviors and facts. It entails climbing the tree and even free fall, cannibalism, scavenging, grouching nature, smell sensing style, coconuts consumption, long survival period, carrying developing young under the abdomen, sea adaptation, enormous growth, and much more.

Since the species is under massive threat, it seems substantial to conserve them and keep away from the dangers.

Kalpana Ghimire holds a post-graduate degree in Environmental Science from Nepal. She possesses numerous research experiences working in water pollution, community forestry, environment conservation status, and wildlife ecology. She was an internee in the Department of Environment (EIA monitoring and auditing section) under the Government of Nepal. Kalpana Ghimire is an avid traveler, an enthusiastic wildlife researcher, and has a huge passion for working in the environment sector. She loves far traveling to the natural areas, conducting field wildlife research and reading the novels.