The coconut crab, also known as the robber crab or palm thief, is a fascinating creature that has captured people’s imaginations for centuries. As the world’s largest land-dwelling arthropod, these enormous hermit crabs can reach surprising sizes. But just how heavy do coconut crabs get? In this article, we’ll take an in-depth look at coconut crab weights.
Coconut crabs live on islands in the Indian and Pacific Oceans. Unlike small hermit crabs that inhabit seashells coconut crabs have adapted to survive on land. Their name comes from their ability to climb coconut palms and crack open coconuts with their massive pincers.
These animals are astonishingly huge compared to other land invertebrates An adult coconut crab can have a leg span over 3 feet across and weigh nearly 10 pounds, Their mammoth size makes them the biggest land-living arthropod on Earth
Average Weight of a Coconut Crab
On average, a fully grown coconut crab weighs between 4-9 lbs. However, some individuals reach even more impressive proportions. The largest coconut crabs can weigh up to 20 lbs!
There is high variation in size between individual crabs. Here are key factors that influence their growth:
-
Gender – Males are generally bigger than females. Males may reach 10 lbs, while females average around 6 lbs.
-
Age – Coconut crabs grow slowly, taking decades to reach full size. Older crabs are typically larger.
-
Food Availability – Crabs with abundant food sources tend to grow larger over their long lifespans.
-
Genetics – Some crabs seem genetically predisposed to grow bigger than others.
So while 4-9 lbs is typical, coconut crabs can vary substantially depending on biological factors.
Why Can Coconut Crabs Reach Such Impressive Weights?
There are a few key reasons why coconut crabs can achieve such giant proportions compared to other land animals:
-
Slow Metabolism – Coconut crabs have an extremely slow metabolic rate compared to other creatures. This allows them to accumulate body mass over many decades.
-
Few Predators – On remote islands lacking large land predators, coconut crabs can live to old age and gain size without constraints from predation.
-
Abundant Food – Tropical islands provide a nutritionally rich habitat with coconuts, nuts, fruits and other plentiful food sources to fuel their growth.
-
Ideal Habitat – Islands offer a hot, humid climate and sandy soils perfect for burrowing. This supports the needs of massive coconut crabs.
Thanks to these advantages, coconut crabs can achieve record-breaking weights and their distinction as the heaviest land invertebrate.
Changes in Weight Over Their Lifecycle
Coconut crabs go through dramatic changes in size and form over their complex life cycle:
-
Larvae – Begin life as tiny larvae about 1/10 inch long. Drift and feed in the ocean for a month.
-
Juveniles – After moving to land, juveniles use snail shells for protection. At around 1/3 inch long, they abandon shells and look more crab-like.
-
Adults – Slowly grow over decades, molting and gradually increasing in size each year. Growth rate varies substantially between crabs.
-
Females mature around 2 inches long and 6 years old. Max out around 6 lbs.
-
Males mature around 3 inches long and 10 years old. Can eventually exceed 10 lbs.
-
So coconut crabs undertake an incredible transformation from microscopic larvae to giant adults possibly weighing as much as a housecat!
The Strength of Large Coconut Crabs
Given their massive proportions, it’s no surprise coconut crabs have incredible strength. They use their giant pincers to crack coconuts, climb trees, and defend themselves. Here are some amazing facts about their power:
-
Coconut crabs can lift over 66 lbs – more than 30 times their own weight!
-
Their pincers generate the strongest pinching force of any land animal.
-
They can break open and eat entire coconuts, exerting over 700 lbs of force with their claws.
-
Coconut crabs can climb over 30 feet up trees.
Clearly, a coconut crab’s giant size translates into remarkable strength. They are not to be underestimated!
Conservation Status of Coconut Crabs
Due to habitat destruction, climate change, overharvesting and invasive species, coconut crab populations have declined substantially across their native range. They are listed as Vulnerable on the IUCN Red List.
Some key threats facing coconut crabs:
- Habitat loss as tropical forests are cleared
- Being caught for food or the pet trade
- Predation on juveniles by introduced rats, pigs and cats
- Deaths from vehicle strikes as roads fragment their habitat
More research and conservation action are urgently needed to protect these animals. Preserving their island habitats will give coconut crabs space to continue reaching impressive sizes.
Summary
Coconut crabs are truly fascinating creatures. Their mammoth proportions and strength are remarkable products of evolution suited for island life. With proper habitat conservation, hopefully coconut crabs can persist at their monumental sizes for years to come.
The next time you see a coconut, consider the colossal crab that can crack it open! Learning about coconut crabs deepens our appreciation for the diversity of life on Earth. Their impressive weights reflect millions of years of adaptation to survive and thrive in island environments.
Up in the trees
Adult coconut crabs live on land, returning to sea only to release their fertilized eggs. They live alone in their burrows, where they usually stay during the day, avoiding the heat and preventing water loss. Even though they are more active at night, on Tetiaroa, especially in the forest of motu Reiono, we often see them up in the trees during daytime hours.
“There is a land crab that you can figure generally on being twice as big as your head. These creatures have very powerful claws and they can open a coconut by crushing the shell. They are also delicious to eat, but should they find their way into your bed, you would be advised to leave immediately. They will fasten onto whatever part of the body is available and their grip can only be released by tickling their behinds.”
Excerpt from M.B’s notes for his atoll, Tetiaroa.
The above excerpt from M.B’s notes for his atoll, Tetiaroa, is a perfect summary of what characterizes a coconut crab.
The most striking thing about these crabs is how big they can grow, which gives them the distinction of being the largest land crabs in the world. The biggest coconut crab ever recorded had a 1m (3ft) leg span and weighed 17 kg. They are also extremely powerful, their claws are strong enough to cut open a coconut to eat it, hence their name.
“Robber crabs” is another name they go by because of their opportunistic behaviour. They prefer coconut flesh or fruits, but they will also eat almost whatever they come across : birds, other crabs, turtles, rats… They have even been seen in kitchen sinks, trying to scrape leftovers from dishes. They have a powerful sense of smell.
The Colossal Coconut Crab | South Pacific | BBC Earth
FAQ
Are coconut crabs legal in the US?
Long story short, someone showed me a coconut crab for sale and the wikipedia says it’s a threatened species. Endangered Species Act says possessing a threatened species is a Class C Felony.
Are coconut crabs good eating?
Yes, coconut crabs (also called robber crabs) are very good eating, wherever they live. There are many popular recipes for them. They tear open coconuts with their claws, so handle with great care! They can easily remove one or more of your fingers.
What is the heaviest coconut crab?
Coconut crabs are the largest terrestrial arthropods on Earth, reaching weights of up to 4.1 kilograms (9 lbs) and leg spans exceeding 1 meter (3 feet 3 inches). Their body structure reflects significant evolutionary adaptations, with a hardened exoskeleton providing protection and reducing water loss.
What do you get for killing coconut crab?
The loot it drops is sprayed around the field similar to a Sprout, however, only you can see and pick up the tokens. You can also pick up all the loot dropped with a token link. The quicker you kill the Coconut Crab, the more Tropical Drinks and Coconuts it will yield.
How big is a coconut crab?
The coconut crab (Birgus latro) is a terrestrial species of giant hermit crab, and is also known as the robber crab or palm thief. It is the largest terrestrial arthropod known, with a weight up to 4.1 kg (9 lb). The distance from the tip of one leg to the tip of another can be as wide as 1 m (3 ft 3 in).
What is a coconut crab?
The coconut crab has been known to western scientists since the voyages of Francis Drake around 1580 and William Dampier around 1688. Based on an account by Georg Eberhard Rumphius (1705), who had called the animal ” Cancer crumenatus “, Carl Linnaeus (1767) named the species Cancer latro, from the Latin latro, meaning “robber”.
How many legs does a coconut crab have?
The body of the coconut crab is, like those of all decapods, divided into a front section (cephalothorax) with 10 legs, and an abdomen. The front-most pair of legs has large chelae (claws) with the left being larger than the right.
What color is a coconut crab?
Depending on where they live, coconut crabs can be deep blue, red, or purple-red in color, or any combination of the three. Their left claw is slightly larger than their right (which is the case for most species of crabs, a phenomenon called asymmetrical chelae), both of which are located near the front of their bodies.
How long does a coconut crab take to grow?
The coconut crab reaches sexual maturity around 5 years after hatching. They reach their maximum size only after 40–60 years. They grow remarkably slowly, and may take up to 120 years to reach full size, as posited by ecologist Michelle Drew of the Max Planck Institute.
What is the largest land crab in the world?
The largest land crab in the world, the coconut crab (Birgus latro) is one of those crabs that spends all of its adult life on land. It shares this lifestyle with a variety of other hermit land crabs but isn’t one itself.