Imagine you are lying in a hammock on the beach, relaxing and enjoying a spot of fresh air, when suddenly a ten-legged beast, measuring about three feet across, starts slowly climbing up the palm tree in front of you, or, worse, drops down right next to you. It'd almost be enough to make you drop your piña colada with horror and run for cover. The coconut crab, the largest crab on land, and indeed world’s largest land-based arthropod, can have that effect on people.
Coconut crabs, also known as robber crabs or palm thieves, might be large – the length of their bodies alone can extend upwards of a foot – but sadly their numbers are not. These huge creatures were once quite plentiful, but thanks to human appetites for crabmeat, they are now on the IUCN Red List as Data Deficient, meaning we don’t know exactly how many are left but that the numbers are most likely low.
Here, we'd like to share some amazing pictures and a few equally amazing facts about these unusual crabs, all of which demonstrates that they’re definitely a species worth preserving.
This photograph should give you some idea of just how big these crabs really are. As you can see, these are two impressively sized critters! The man holding them is obviously either very brave or familiar enough with coconut crabs to know how to handle them. As mentioned earlier, these crabs can grow up to a foot in length, sometimes more, but it is not only their body size that is arresting – just look at those claws!
Here’s a wonderful specimen of this giant crab from Christmas Island. The photographer, Eddy Rademaker, reports that this particular crab measured 18 inches across! Rademaker was careful to stay out of reach of those pincers while taking this picture, which sounds like a very wise idea. If you want to see a coconut crab in the wild for yourself, Christmas Island is a good destination as it reportedly has the biggest population of the species in the world.
Blue is the most common color for coconut crabs, although they can also be found in more orangey or reddish shades. The coconut crab is actually not a proper crab at all, but rather a type of hermit crab. Whereas true crabs have smaller abdomens that they tuck under their bodies, coconut crabs – as you can see from this picture – have large abdomens that are hardened for protection, like those of lobsters.
Those pincers may look pretty powerful, but how effective they are at cracking open coconuts on their own is debatable. They can, however, be used to tear the husks off coconuts, as well as to cut open fruit, shred carrion – or even, in one reported incident, to catch and eat a rat. You certainly wouldn’t want to tangle with those pincers. As a creepy aside, coconut crabs may even have been responsible for the disappearance of legendary aviator Amelia Earhart’s body, as reported by Environmental Graffiti here.
This has to be one happy coconut crab: it’s enjoying its namesake meal, after all. Coconut crabs have a few tricks up their sleeves (or do we mean claws?) when it comes to getting inside the hard exterior of the fruit. One method observed is that the crabs climb up a palm tree, coconut in tow, and drop it from a height. The crab itself then drops from the tree (which they can do from a height of 15 feet, unharmed) to hopefully find its meal conveniently cracked open from the fall.
Coconut crabs use the pointed tips of their second and third pairs of legs and the pincer-like endings on their fourth legs to climb trees. They can get up to 20 feet high this way, which must be quite a sight for those who aren’t expecting it. Once they’re up there, they can drop the coconuts they're carrying to be broken open on the ground below.
We’re not sure what’s at the top of the tree that has interested this coconut crab so much. Maybe some fruit? Coconut crabs have a very keen sense of smell and can detect the odor of fruit, or rotting flesh, from a long way off. This is just as well, since the crabs don’t see very well, although they can detect vibrations in the ground, much the way snakes do.
Coconut crabs, like this one pictured on Palmyra Atoll, south of Hawaii, are scavengers that sometimes mistake human objects for food. This is the origin of their other names, ‘robber crab’ and ‘palm thief’. They especially like shiny items and, during WWII, were known for stealing from soldiers’ trenches.
Once again, here are a couple of Christmas Island crabs. According to photographer John Tann, this is a rather curious critter that wandered up to him for a closer look. Although this is obviously a daytime snap, coconut crabs are actually mostly nocturnal. During the day, they either hide in crevices or dig themselves burrows in sand or loose dirt.
The beautiful blue hue of this Cook Islands crab makes it look lovely, rather than scary. However, as you can see, in comparison to the person holding it, it’s still one very large arthropod. The front claws alone are enormous! You can also see in this picture how the coconut crab's body is divided into two sections – the front and the abdomen. Also clearly visible are the crab’s four front pairs of legs. The fifth pair is normally kept tucked into the upper part of the exoskeleton, or carapace.
It’s not only the juicy contents of the coconut that these crabs use, either. They also utilize the husks, like those pictured, to line their burrows. Once in their underground lairs, coconut crabs seal the entrance, using their large pincers as spades. This serves the double purpose of both keeping the crabs protected and ensuring that the air in their burrows is kept nice and damp, making it easier for them to breathe.
Here's another coconut crab, looking a little spider-like, on its way up to grab a tasty coconut snack. On some islands, these formidable creatures have spiritual significance. For example, Mariana Islanders believe that the crabs may be the returned spirits of deceased humans.
The name coconut crab doesn’t necessarily refer only to the species’ diet. When they are young (like this one), coconut crabs will use the discarded shells of mollusks or gastropods for protection, just as hermit crabs do. When they can’t find a suitable mollusk shell, they will occasionally use a coconut’s. Then, once they’ve grown their own hardened exoskeleton, they no longer need to use these second-hand coverings.
One reason for the massive size of coconut crabs is that they continue to grow all through their lives – which can span 60 years! So the bigger a crab, the older it is. Although they are not the largest species of crab (there are bigger specimens in the ocean, with the Japanese spider crab the largest of all living arthropods), they are certainly the largest that live on land.
Here’s another formidable looking crab. Note the gorgeous blue and purple colors of its exoskeleton. Although unlikely to attack a person unprovoked, a coconut crab will snap at someone they consider threatening. And just in case you are ever caught in one of those vice-like grips, you can try a trick reportedly used by the Micronesians; that is, tickle the crab on the soft parts of its body until it lets go. Better yet, stay out of the crabs’ way in the first place!
Looks like it’s time for this coconut crab to leave the tree hollow and go look for some food. According to Ryshard Antonio, who took this photograph, the crabs are easier to hear than to see at night. They apparently make a loud clanking noise that he describes as being similar to a rock hitting the ground. Not hard to believe, looking at those huge pincers.
Coconut crabs have a wide-ranging habitat and can be found on shores in both the Indian and Pacific Oceans; like this one, from Sesoko Island, Japan. We love its stylish-looking blue stripes! Unfortunately for coconut crabs, their shells are prized as souvenirs, just as their meat is sought after for eating. Because of human appetites, the crabs no longer exist in heavily populated areas like Australia, Indonesia, New Guinea or Madagascar. And they face a similar fate in places like Guam and the Solomon Islands.
Although it might seem impossible to stop the harvesting of these tough yet vulnerable creatures entirely, several countries, including Guam and Vanuatu, are trying to minimize the dangers to their coconut crab populations. The nature reserve of Palmyra Atoll also provides the crabs with a safe habitat in which to live. While farming the creature has also been considered, a lot still has to be learned about coconut crab reproduction for this to be viable.
Hopefully, these combined efforts will see coconut crabs continue to climb palm trees, grow to amazing sizes, and live out their long lives for generations to come.