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.

Need to Cure of Case of Cabin Fever? Try Backyard Birding

Baltimore orioles are colorful spring migrants.
Baltimore orioles are colorful spring migrants.
Brittany Tande/iStock via Getty Images

No matter how many virtual tours and online classes you take, it's hard not to go a little stir-crazy after weeks of social distancing. If you're already sick of activities that require you to stare at a screen, consider seeking out real-life entertainment in your backyard. As Auburn Pub reports, the New York State Department of Environment Conservation is recommending that residents take up birdwatching during the COVID-19 pandemic. However, they stress that it's important to continue to practice social distancing.

Zoos, beaches, and even some national parks are currently closed to the public, but you don't have to travel far to get your daily dose of nature. Spring is in full bloom, and many bird species are currently in the midst of migrating from their winter homes down south to northern states. That means that even urban areas like New York City are becoming places for birds to nest and raise their young.

Local parks are great spots to observe birds while keeping your distance from others, but a trip off your property isn't necessary. If you have a backyard, or even just a tree on the street outside your home, you can watch birds from a patio, balcony, or through a window.

Birding is more than just a way to pass the time when activities are limited. A 2017 study from the University of Exeter found that being able to see birds around your home may reduce levels of stress, depression, and anxiety. If you use birding as an excuse to get out of the house, those benefits may be even greater as being outdoors in general has been shown to boost several facets of mental health.

If you're interested in using your time in isolation to get into birding, there are many resources online you can use. Watch this beginner's guide to birding and read these facts about the birds in your backyard before you get started.

[h/t Auburn Pub]

Beyond Tiger King: 10 Fascinating Animal Documentaries You Can Stream Right Now

A scene from Catwalk: Tales from the Cat Show Circuit (2018).
A scene from Catwalk: Tales from the Cat Show Circuit (2018).
Markham Street Films

By now, you've probably already binged Netflix's bewilderingly bonkers docuseries Tiger King (2020). If you're ready to dive deeper into the animal kingdom, there are plenty more documentaries out there. From wildcats to whales, these 10 films will take you on a cinematic adventure around the world, introducing you to captivating creatures and the people who love them.

1. The Tigers of Scotland (2017)

The Tigers of Scotland (2017) brings viewers as up close and personal as possible with a small but mighty feline: the Scottish wildcat. The film delves into the efforts to conserve the disappearing Highland tiger, as well as the history and mythology surrounding the UK’s only “big cat.”

Watch it: Netflix, Amazon, iTunes

2. Ghost of The Mountains (2017)

This 2017 Disneynature documentary will transport you to the world’s highest plateau in search of a family of snow leopards. These cats are famously tough to find, so Ghost of the Mountains offers viewers behind-the-scenes footage of what it’s like to track the elusive beasts.

Watch it: Netflix, Google Play, Youtube

3. Catwalk: Tales from the Cat Show Circuit (2018)

This delightful documentary takes you deep into the competitive cat show circuit. Both charming and at times cutthroat, the film brings viewers on a journey to see which of the many cool cats and kittens will be crowned Canada's top cat.

Watch it: Netflix

4. Kingdom of the White Wolf (2019)

Follow along as a National Geographic explorer and photographer embeds with a white wolf pack in the high Arctic. These wild wolves aren't used to seeing people, giving the filmmakers—and audience—an intimate window into the pack's daily lives and familial bonds. In addition to showcasing captivating footage of the animals, the three-part docuseries also features sweeping views of the starkly beautiful Ellesmere Island.

Watch it: Disney+, YouTube TV

5. Dogs (2018)

This docuseries, which highlights various dogs and their humans from around the world, celebrates the bond between people and their pups. But it’s more than just a montage of feel-good moments about humankind’s best friend: Each episode tells a broader tale about the human condition, crafting an emotional narrative that pulls at the heartstrings like a puppy tugging on a toy.

Watch it: Netflix

6. Dancing with the Birds (2019)

These birds will put your dad moves to shame. Watch the male avian performers shimmy, shake, and flash their feathers while attempting to woo their female mates. The documentary, narrated by Stephen Fry, offers a colorful look at the wonderfully wacky world of bird mating rituals.

Watch it: Netflix

7. Honeyland (2019)

This documentary follows Hatidze Muratova, one of the last wild beekeepers in a remote village in North Macedonia. She lives with her ailing mother, nurturing a traditional way of beekeeping passed down through the generations and striking a balance between making a living and maintaining ecological balance. But everything changes when a nomadic family settles nearby, threatening Muratova’s way of life. The resulting story is both sweet and stinging.

Watch it: Hulu, Amazon Prime, YouTube, Google Play

8. Virunga (2014)

This 2014 documentary highlights the park rangers fighting to protect the Congo’s Virunga National Park, home to the critically endangered mountain gorilla. As poaching and oil exploration threaten the park, the rangers and conservationists risk their lives to guard the rare creatures that inhabit it.

Watch it: Netflix

9. Harry & Snowman (2016)

In the 1950s, Harry deLayer bought Snowman, a run-down plow horse destined for slaughter, for just $80 at an auction. Within months, the two were taking the show jumping circuit by storm, launching both horse and rider to new heights. This documentary tells the story of the friendship the two developed, and chronicles their lives both in and out of the competitive spotlight.

Watch it: Amazon Prime

10. The Whale and the Raven (2019)

The waters around Canada’s Great Bear Rainforest are a haven for whales, who feed and find refuge in the quiet channels. With stunning visuals, this documentary highlights the tension of a community’s push to protect its wild places against the pressures of the ever-encroaching natural gas industry.

Watch it: Amazon Prime

SECTIONS

arrow
LIVE SMARTER