10 Ginormous Facts About Coconut Crabs

Janos/iStock via Getty Images
Janos/iStock via Getty Images

They're huge and antisocial. They will steal your silverware and can rip apart whole coconuts with their claws. Grab a piña colada and enjoy these 10 ginormous facts about the amazing coconut crab.

1. Coconut crabs are colossal.

Native to islands in the Indian and southern Pacific oceans, are truly humongous. They can weigh 9 pounds and measure 3 feet from leg to leg. Coconut crabs are the largest land-living arthropods—the phylum of joint-legged creatures that includes crabs, insects, spiders, and scorpions. Even Charles Darwin was stunned by their “monstrous size.”

But be aware: Occasionally, a viral photo circulates that exaggerates the coconut crab’s size. As biologist Michael Bok explains, the coconut crab in that infamous photo is normal sized, but the trash can is unusually small.

2. Coconut crabs are actually hermit crabs.

Coconut crab
Sandwich, Flickr // CC BY-NC-ND 2.0

Where does such a bizarre animal fit in the animal kingdom? Are they lobsters? Tarantulas? Space aliens? In fact, Birgus latro is a kind of hermit crab.

You may have seen smaller hermit crabs on a trip to the beach—or for sale at a pet shop. They take shelter inside abandoned snail shells, carrying them around as portable homes. But if coconut crabs are hermit crabs, then why don’t they live in shells? Well, they do—when they’re young and still small.

3. Coconut crabs quickly outgrow their borrowed shells.

Like other crabs, hatchling coconut crabs begin their lives floating freely at sea. After about a month of eating and growing, they find a snail shell and move in. The little coconut crabs carry this mobile home as they begin to transition to a land-based life.

A seashell is a nice, protected place to live, but it has its drawbacks [PDF]. As a crab gets bigger, its shell gets tighter—like an old pair of shoes on a kid who’s growing fast. The crab needs to find a bigger shell and make a quick switch. And that larger home will be heavier to tote around.

So, after a year or so of inhabiting shells, the coconut crab makes a major lifestyle change. It crawls out and hardens the parts of its body that were once protected by the shell by regrowing layers of calcium-based tissues, a process called recalcification. Without its old home, it’s free of size constraints. Now, unlike other hermit crabs, it can become enormous.

4. Coconut crabs eat coconuts, of course ...

This might seem obvious from the coconut crab’s name. But if you’ve ever tried to crack open a coconut, you know that it’s a steep challenge. In fact, a lengthy scientific debate once raged about whether coconut crabs were really able to open the fruit. It turns out that they’re up to the challenge—but they don’t just pop open their prize and dig in.

Breaking into a coconut is a mighty ordeal even if you’re a heavily armored crustacean the size of a small dog. Coconut crabs first use their claws to scrape away the fibrous coating. This can take hours or days. Finally, they stab into the fruit at a weak point and rip it open.

This diet helps coconut crabs grow large: those with access to coconuts may be twice as massive as those without. But eating the fruit isn’t essential for their survival. So what other items do the largest land-living arthropods shove into their maw?

5. ... but they also eat dead animals, their own body parts, and each other.

As well as the occasional biscuit, as you can see in the video above. (Note: Do not feed biscuits to coconut crabs.) A coconut crab’s diet may include other tropical fruits, fallen plant material, dead and decaying animals, rats, and other crab species. They’ll even eat members of their own kind. In fact, biologist Mark Laidre says they only relatively recently evolved to eat coconuts—a skill unique to modern coconut crabs—which helps them to eat each other less.

They also eat their own discarded body parts. As coconut crabs grow, they periodically molt their tough outer layer (the exoskeleton) and grow a new one. Once they’re done molting, which takes about a month, they gobble up their own exoskeleton.

6. Coconut crabs have an amazing sense of smell ...

Coconut crabs often forage at night. How do they find food when they’re wandering around in the dark? They sniff it out. These animals have a strong, highly efficient [PDF] sense of smell. In fact, a large portion of their brain is devoted to detecting odors.

7. ... which might explain why they're thieves.

Coconut crabs are also known as robber crabs because they snatch silverware and other objects and carry them away. Some people have even advanced the gruesome theory that Amelia Earhart’s remains are missing because coconut crabs hauled them down into their burrows. The thievery might be tied to that incredible sense of smell. Coconut crabs ignore objects that have been washed clean of scents, suggesting that they may only abscond with things that carry a faint whiff of food.

8. Coconut crabs are pretty antisocial.

Adult coconut crabs live alone in crevices or burrows. They aggressively guard their privacy; a crab entering another’s burrow risks becoming a meal.

But that’s not the end of their antisocial behavior. When coconut crabs emerge to feed, they keep their distance from each other. To maintain their personal space, they’ll announce their presence with ritualized claw waving. Laidre sought to find out if coconut crabs ever gathered together to interact (beyond mating or eating each other). The scientist tethered coconut crabs to one spot and watched to see if any others came to visit. They did not.

9. Coconut crabs carry their developing young under their abdomens.

After coconut crabs mate, females attach their eggs to special appendages and carry them under their abdomens. While the young develop inside the eggs, the females hold onto them, sticking near the edge of the sea so that they can periodically moisten the eggs.

But this care ends when the young are ready to hatch. The females release their hatchlings into the ocean waves. Now the tiny, floating babies must fend for themselves—and only a few will survive to return to land.

10. We need to learn a lot more about coconut crabs.

Coconut crab
Anne Sheppard, Wikimedia Commons // CC BY 3.0

Coconut crabs are little-studied creatures, and we need to know more about them—not just because they’re incredible and have a lot to tell us about biology, but also because we want to keep them around.

They may be huge and heavily armored, but they can be vulnerable. Coconut crabs take an extremely long time to grow big—they can live more than 40 years—and introduced predators such as rats can harm smaller, younger individuals or those in the process of shedding their exoskeletons (when their bodies are soft). Habitat loss has also caused local declines in some areas. The International Union for Conservation of Nature lists the coconut crab as data deficient: That is, we don’t know enough about its locations and populations. That’s why we need to study and learn more about these amazing, otherworldly critters.

100 Dachshunds Competed in Cincinnati’s Annual ‘Running of the Wieners’

NORRIE3699/iStock via Getty Images
NORRIE3699/iStock via Getty Images

Every year, to kick off Cincinnati’s Oktoberfest Zinzinnati, 100 dachshunds compete in heats to decide who the fastest dachshund in the Midwest is. This year marks the 43rd annual Oktoberfest—one of the biggest Oktoberfest celebrations outside of Germany (more than 500,000 people attend the three-day event).

On the afternoon of Thursday, September 19, 100 wiener dogs (and their owners and handlers) gathered in downtown Cincinnati for the 2019 "Running of the Wieners." The dogs, dressed in hot dog costumes, ran 10 heats, which lasted 75 feet or five seconds each. The winner of each heat advanced to the final round, where the top three finishers were decided.

Maple, a long-haired, one-year-old dachshund, ran his way into first place—and into our hearts.

Maple’s owner, Jake Sander, told WCPO that Maple is one of five dachshunds in the family, and that he learned to run fast by chasing his brother around. Leo and Bucky, two other doxies, placed second and third, respectively.

Besides the Running of the Wieners, Zinzinnati also hosts the World’s Largest Chicken Dance. However, the wiener dogs are more fun to watch.

Photographer Captures Polka-Dotted Zebra Foal in Kenya

Frank Liu
Frank Liu

Zebras are known for their eye-catching patterns, but this polka-dotted foal recently photographed in Kenya's Masai Mara National Reserve really stands out from the herd. As National Geographic reports, the zebra baby likely has pseudomelanism, a rare pigment condition that's been observed in the wild just a handful of times.

Nature photographer Frank Liu saw the zebra foal while looking for rhinos in the savannah wilderness preserve. After initially confusing the specimen for a different type of animal, he realized upon closer inspection that it was actually a plains zebra born with spots instead of stripes. The newborn foal was named Tira after the Maasai guide Antony Tira who first pointed him out.

Zebra foal with spots walking with mother.
Frank Liu

Zebra foal with spots.
Frank Liu

A typical zebra pattern is the result of pigment cells called melanocytes, which are responsible for the black base coat, and melanin, which gives the animal its white stripes. (So if you've ever wondered if zebras are white with black stripes or black with white stripes, the answer is the latter). In Tira and other zebras with pseudomelanism, the melanocytes are fully expressed, but a genetic mutation causes the melanin to appear as dots rather than unbroken stripes.


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Though rare, this isn't the only time a zebra with pseudomelanism has been documented in nature. Pseudomelanistic zebras have also been spotted in Botswana’s Okavango Delta, but Liu believes this could be the first time one was found in the Masai Mara preserve.

Zebra stripes aren't just for decoration. The distinct pattern may act as camouflage, bug repellant, and a built-in temperature regulation system. Without these evolutionary benefits, Tira has a lower chance of making it to adulthood: Pseudomelanistic zebra adults are rarely observed for this reason. But as Liu's photographs show, the foal has the protection and acceptance of his herd on his side.

[h/t National Geographic]

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