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.

9 Tiny Facts About the Chevrotain

Dave Curtis, Flickr // CC BY-NC-ND 2.0
Dave Curtis, Flickr // CC BY-NC-ND 2.0

With a round body, spindly legs, and long fangs, this odd creature gives the platypus a run for its money. Also known as the mouse deer, chevrotains are shy and mysterious, and not much is known about them. But here's what we do know.

1. Chevrotains are not mice, nor are they deer.

Lesser mouse deer or chevrotain
BirdHunter591/iStock via Getty Images

At first glance, these animals look like a weird mash-up of a deer, a mouse, and a pig. Mouse deer share a suborder with deer (Ruminantia) but are not considered “true deer.” They have their own family, Tragulidae.

2. Chevrotain species vary by weight.

Mouse deer in Thailand
MonthiraYodtiwong/iStock via Getty Images

These creatures are way smaller than any deer. Depending on the species, a chevrotain can weigh anywhere from 4 to 33 pounds. The smallest species is the lesser Malay, while the largest is the water chevrotain. No species gets any larger than a small dog.

3. There are a lot of different kinds of chevrotains.

Mouse deer
aee_werawan/iStock via Getty Images

This tiny animal comes in many variations. The family has been classified into two genera: true chevrotains (Hyemoschus) and the mouse deer (Tragulus). The spotted mouse deer are still very mysterious, so scientists have placed them in their own genus called Moschiola. Despite being categorized in different genera, they all share a similar look.

4. Chevrotain fangs are fiercer than Dracula's.

Chevrotain in a woodland
BirdHunter591/iStock via Getty Images

Open up a chevrotain’s mouth and you’ll find two long fangs. They're especially elongated in males, which use the needle-like canines to stab each other. Thanks to an extra thick coat and robust muscles around the neck and rump, these adorable fighters are protected from bites during combat.

5. Some consider the chevrotain a living fossil.

Chevrotain sticking its tongue out
Josh More, Flickr // CC BY-NC-ND 2.0

Chevrotains are the most primitive of ruminants. Like deer and similar hoofed animals, they have even-toed hooves and a multi-chambered stomach. But unlike deer, chevrotains have a three-chambered stomach instead of four, and they lack horns or antlers. They haven't changed or evolved much during their time on Earth. Scientists see them as an evolutionary link between ruminants and non-ruminants.

6. Taking a dip is the water chevrotain's best defense.

The water chevrotain is known for its ability to dive underwater when it senses a predator nearby. The miniature swimmers scrunch up and walk on the bottom of rivers and streams to prevent being picked up by the current. If there are any reeds or plants around, the animals will grab them to stay tethered. Chevrotains are able to hold their breath for about four minutes.

While hiding from hungry predators, the water chevrotain can reemerge to get some air before diving back down. Still, the animal tires easily, and can only swim for short periods of time.

7. Childbirth is an expedited experience for chevrotains.

Chevrotain in a woodland
aee_werawan/iStock via Getty Images

After getting pregnant, a female chevrotain will carry the offspring for five to nine months, depending on the species. The baby can usually stand on its own within one hour of being born. Mothers will visit their young periodically for feedings and stand on three legs while nursing.

Chevrotains are known for their ability to be almost continuously pregnant—greater and lesser Malay mouse deer can mate again only a few hours after giving birth.

8. Chevrotains are shy wallflowers.

Chevrotain in a woodland
cowboy5437/iStock via Getty Images

Due to their small size, chevrotains are preyed upon by many different animals. Lacking antlers or horns for protection, the tiny animals are forced to lead secluded lives. Some species are nocturnal and very rarely seen. Chevrotains are very shy and often graze alone, only coming together to mate. They communicate with a series of smells and noises; this timid behavior makes it difficult for scientists to study them.

9. Chevrotain hooves make a lot of noise.

Chevrotain in a woodland
asxsoonxas/iStock via Getty Images

Although normally peaceful, a male will angrily beat his hooves when agitated—they can stomp around four to seven times a second. This “drum roll” technique wards off predators and warns other chevrotains in the area that there’s danger.

Additional sources: "Water Chevrotain," Amazing Animals of the World; "Chevrotains (Tragulidae)," Grzimek's Animal Life Encyclopedia; Mammals IV, Gale Virtual Reference Library

'Lost Species' of Tiny, Rabbit-Sized Deer Photographed in Vietnam for the First Time in 30 Years

Global Wildlife Conservation
Global Wildlife Conservation

The silver-backed chevrotain, also called the Vietnamese mouse-deer, is elusive. It's so elusive that scientists had feared it was extinct after none had been photographed for decades. But as The Washington Post reports, the first images taken of the mammal in nearly 30 years prove that the species is still alive in the woods of Vietnam.

No larger than small dogs, chevrotains are the tiniest ungulates, or hoofed animals, on Earth. They have vampire-like fangs and skinny legs that support their bodies. Silver-backed chevrotains are characterized by the silver sheen of their tawny coat.

The tiny population native to Vietnam has been devastated by poachers in recent decades. That, and the animal's natural shyness, make it incredibly difficult to study. Before this most recent sighting, the last time scientists had recorded one was in 1990.

Global Wildlife Conservation, the Southern Institute of Ecology, and the Leibniz Institute for Zoo and Wildlife Research teamed up in hopes of documenting the lost species. Researchers interviewed residents and government forest rangers in the Vietnamese city of Nha Trang about the silver-backed chevrotain, looking for tips on where to find one. Residents said that while populations had been hit hard by hunting, the animals were still around.

Based on this local ecological knowledge, scientists set up three camera traps in the Vietnamese woods. In just five months, they captured 275 photographs of the little mouse-deer. They then installed 29 additional cameras and snapped 1881 new images in that same length of time.

“For so long this species has seemingly only existed as part of our imagination," Global Wildlife Conservation associate conservation scientist An Nguyen said in a statement. "Discovering that it is, indeed, still out there, is the first step in ensuring we don’t lose it again, and we’re moving quickly now to figure out how best to protect it.”

Now that a silver-backed chevrotain population has been located, researchers plan to conduct the first-ever comprehensive survey of the species. Once the data is collected, it will be used to build a plan for the species' survival.

[h/t The Washington Post]

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