You may have seen hermit crabs before. They are cute and often very small crustaceans that walk along the beach carrying seashells around with them.
Meet their enormous relatives, coconut crabs. They have amazing grip strength and can lift things that are as heavy as a 10-year-old child. Their legs can reach up to a meter in length.
Coconut crabs (Birgus latro) might seem unusual: theyre absurdly large, land-dwelling, bird-hunting crustaceans. But on their isolated island homes, their peculiar traits work incredibly well for them.
Crabs come in all shapes and sizes, from tiny pea crabs to giant monsters with legs spanning over 12 feet across. But what is officially the biggest crab species in the world? And just how big do these colossal crustaceans get?
In this article, we’ll explore some of the largest crab species on the planet and learn what makes them so massive. From giant Japanese spider crabs to coconut crabs that climb trees, keep reading to discover the biggest crabs out there.
The Japanese Spider Crab – The Undisputed Giant
The Japanese spider crab holds the title of the biggest crab in the world. These enormous crustaceans inhabit the waters around Japan and have the largest leg span of any arthropod on earth.
Their spindly, arched legs can extend over 12 feet from claw to claw Their bodies can grow to be 15 inches wide And they can weigh up to 42 pounds.
Japanese spider crabs prefer to live at depths of 160-2,000 feet. During the day, they hide in holes or crevices. At night, they emerge to scavenge for food along the seafloor. They use their long legs to feel around for dead animals, plants, and smaller prey to eat.
One reason they grow so large is their long lifespan. Japanese spider crabs can live to be 100 years old. They reach maturity around 5 years old and just keep growing from there.
Females carry between 1.5 and 2 million eggs at a time. But even with this high reproductive rate, Japanese spider crabs are still considered vulnerable to extinction due to overfishing.
The Tasmanian Giant Crab – Another Massive Crab
While not as big as the Japanese spider crab, the Tasmanian giant crab comes in as a close second for size. These giants are found off the coast of Tasmania, Australia.
Tasmanian giant crabs have a carapace (shell) that can measure nearly 18 inches wide. Their legs span almost 10 feet. And they can weigh over 20 pounds. That makes them the second biggest crab after their Japanese cousins.
These crustaceans live in deep, cold waters where they scavenge dead animals and debris for food. Their huge size helps them crack open larger shells.
Tasmanian giant crabs are commercially fished for their meat. Sustainable harvesting is important for conserving this giant crab’s numbers in the wild.
Coconut Crabs – The Largest Land Crabs
Coconut crabs have the impressive distinction of being the largest land-dwelling arthropod on Earth. Unlike most crabs that live in the water, these giants inhabit tropical islands and can grow up to 3 feet long from leg tip to leg tip.
These massive crabs earned their name from their ability to climb coconut trees. Using their strong claws, they can chop through coconut husks to eat the meat inside.
Coconut crabs are also opportunistic scavengers. They’ll eat fruits, nuts, seeds, smaller animals, and carrion. Anything is on the menu! Their powerful claws can lift over 60 pounds.
Being terrestrial rather than aquatic, coconut crabs cannot swim. But they still require water and will drown if kept underwater for too long. Their gills must be kept moist in order for them to breathe.
Giant King Crabs of Alaska
The frigid northern waters of Alaska are home to some of the biggest king crab species around. The two giants are the red king crab and blue king crab.
Red king crabs have legs spanning 5 feet and can weigh up to 28 pounds. You can identify them by their spiky red shell and black-tipped claws. Meanwhile, blue king crabs grow to 20 pounds heavy with a leg span over 6 feet.
These monster crabs use their vice-like claws to feed on animals like clams, worms, and fish. Slow-moving and largely defenseless prey are no match against these colossal crustaceans.
King crabs are heavily fished for their legs which are a delicacy. Fishery regulations help prevent overharvesting.
Other Giant Crabs Around the World
While the crabs described so far take top honors for size, there are several other giant crab species found across the world’s oceans:
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Dungeness crabs off the Pacific Northwest can weigh up to 5 pounds.
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Snow crabs in the frigid Arctic and Atlantic oceans can reach 6 pounds.
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Giant mud crabs in Asia have shells over 11 inches wide.
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Red rock crabs off the Pacific coast grow to 6 inch shells.
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European spider crabs span 3 feet across.
So while the Japanese spider crab reigns supreme in terms of sheer size, giant crabs can be found scuttling across sandy seafloors worldwide. What accounts for their hulking proportions compared to other crabs?
Why Are Some Crabs So Large?
Most crab species have an average size in the 1 to 3 inch range. So why do some varieties evolve into such monstrous proportions? There are a few key reasons:
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Long lifespans – Many giant crab species live exceptionally long lives, allowing them more time to grow. Japanese spider crabs can reach 100 years old.
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Plentiful food sources – Large crabs often inhabit energy-rich environments like the cold, nutrient-packed waters of Alaska. Abundant food fuels their growth.
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Lack of predators – Giant crabs outgrow most predators. Their formidable claws also deter potential threats. Their immense size removes any pressure to stay small.
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Competition for mates – For male king and spider crabs, growing gigantic helps them compete to mate with females and pass on their genes.
So while genetics play a role, the environment and behavioral adaptations are key factors allowing certain crabs to become true sea monsters. Their huge size lets them dominate as opportunistic feeders and survivors in their ecosystems.
Giant Crab Conservation
While fascinating, many giant crab species are susceptible to overfishing due to their long maturation times and sensitivity to habitat disturbances. Conservation efforts are aimed at:
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Preventing overharvest through strict fishing quotas and regulations
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Protecting sensitive egg-bearing female crabs
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Monitoring populations and managing sustainable fisheries
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Maintaining healthy ecosystems and seafloor habitats
When fishing practices and habitats are managed properly, giant crab species can continue thriving at sustainable levels. While giants like the Japanese spider crab may look intimidating, they are a key part of healthy ocean ecosystems.
Can You Eat Giant Crabs?
Giant crabs are prized by seafood lovers for their succulent, tasty meat. The long legs of king crabs are most commonly eaten, as well as the thick claws. The body meat tends to be less desirable.
However, some environmental groups recommend avoiding king crab to help protect declining populations, especially vulnerable red king crabs. Farmed crabs and abundant species like Dungeness are more sustainable options.
As always, educated seafood choices help support healthy wild fisheries and ensure we can enjoy these ocean giants for generations to come through conservation and management.
Nature’s Colossal Crustaceans
From the tree-climbing coconut crab to the tremendous Japanese spider crab, giant crabs astound us with their immense proportions and strength. They play a vital role as opportunistic feeders in marine and coastal environments.
While humans may feel intimidated seeing a 5-foot crab leg at the seafood counter, these massive crustaceans help maintain balance in the ecosystems they inhabit. Their unique adaptations allow them to survive and thrive at impressive sizes.
So next time you crack open a crab leg, take a moment to appreciate the wonders of evolution that created nature’s giants. With careful stewardship, future generations can continue to enjoy these colossal creatures of the sea.
What is a coconut crab?
To say that coconut crabs are big would be an understatement.
Theyre a mega-crab, really, explains Miranda Lowe, Principal Curator of Crustacea at the Museum. They range, but they can be huge – up to a metre leg span.
For that honor, the Japanese spider crab (Macrocheira kaempferi), which can grow up to 3 feet long, reigns supreme. 7 metres from claw to claw.
But the coconut crab is the largest crustacean that spends all its adult life on land, with a Guinness World Record to prove it. Its also the biggest land-dwelling arthropod, the group of invertebrates that also includes insects, spiders and centipedes.
Coconut crabs can live up to 60 years, reaching sexual maturity at about five years old. They mate between May and September and females release their eggs into the water.
When they hatch, the larvae disperse on floating coconuts, logs or other rafts for four to six weeks. Then, they change into glaucothoe, which look like shrimp, and sink to the bottom of the ocean to find a gastropod shell that will protect them. After that, they’ll start to move closer to the shore and spend another four weeks near the high tide mark before they turn into young crabs. Â.
Coconut crabs only protect their bodies with shells whilst they are juveniles © Drew Avery via Flickr (CC BY 2.0)
Once they become adults, they don’t need gastropod shells anymore. Instead, their tough exoskeleton keeps them safe from damage.
Although they spend their multiple larval stages in water, when coconut crabs eventually become adults, they cant swim. In fact, they drown if they end up underwater for a prolonged period. This is because instead of gills, they have branchiostegal lungs that allow them to breathe air.
From islands off the coast of Africa near Zanzibar to the Gambier Islands in the eastern Pacific Ocean, you can find coconut crabs. They are typically found in coastal forests with plenty of rock crevices and soil for digging burrows. On some islands, they can be found up to six kilometres from the shore.
What do coconut crabs eat?
Coconut crabs are known to eat the white flesh inside green coconuts. Their name may give it away.
Miranda says that their walking legs are shaped like claws and are curved. They have an inward grip that lets them climb palm trees and other trees.
Curved legs and an inward grip make coconut crabs excellent climbers © KYTan via Shutterstock
Coconuts arent all theyll munch on, however. Coconut crabs will eat fallen fruit, nuts and seeds.Â
Perhaps unexpectedly for crabs, they are also rather ruthless predators.
Other crabs only live near or in the water, and they eat dead animals like marine worms and the meat of other dead crabs among other things. Theyre not exactly vicious hunters.
Coconut crabs, however, are known predators of rats, others of their own species and even large migratory seabirds, such as boobies that they find nesting on their islands. They have been spotted mounting attacks in the dark of the night and grabbing unsuspecting prey that pass too close to the crabs burrows.
Miranda says, Its an adaptation because of their food source. On land, some of the time they have to find something else other than coconuts.
Coconut crabs broad diets have even led some to suggest that the reason famed aviator Amelia Earhart was never found when she disappeared mid-flight over the Pacific Ocean was because she was devoured by coconut crabs after perishing on Nikumaroro island.Â
Coconut crabs have a varied diet including fruits, seeds and animals such as rats and seabirds © fearlessRich via Wikimedia Commons (CC BY 2.0)
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What is the biggest crab in the world?
Either way, a steady diet can assist certain crab species in growing to incredible sizes. The biggest crab in the world, the Japanese spider crab, is capable of achieving a leg span of more than 13 feet (4 meters) across. Read on to get better acquainted with the Japanese spider crab, plus discover eight more of the largest crabs out there.
How much does a giant crab weigh?
The Tasmanian giant crab is one of the largest crabs in the world, reaching a mass of 17.6 kg (39 lb) and a carapace width of up to 46 cm (18 in). Among crabs, only the Japanese spider crab ( Macrocheira kaempferi) can weigh more.
What is the largest red king crab ever recorded?
The largest Red King Crab ever recorded was caught in the Bering Sea in 1977. It weighed 28 pounds and had a leg span of 5 feet. This is still an impressive size for a crab, but it falls short of the record held by the Giant Spider Crab. Despite this, Red King Crabs have been known to break records in other ways.
How much does a king crab weigh?
The Colossal King Crab is the largest species of king crab, and can weigh up to 20 pounds (9 kg). Jumbo King Crabs are also quite large, with a weight of up to 10 pounds (4.5 kg). King crabs are known for their impressive size, with some individuals reaching up to 24 pounds in weight and a leg span of 5 feet.