We’ve all seen the photos that made the rounds a few years back: a furry little critter beams at the camera, at a leaf, at a tourist. From this adorable gallery—which naturally went viral—we can discern two facts: 1) that the furry little critter is called a quokka and 2) that this quokka must be the world’s happiest animal. It even says so, right there in the photo gallery.

But life is rarely so simple. It may be known for its sweetness, but the quokka has a salty side. What is a quokka, anyway? How do you pronounce its name? And are they really that happy-go-lucky? Read on for a reality check, and the sobering truth behind that smile.

1. The quokka is a marsupial.

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Quokkas are nocturnal marsupials. They’re some of the smallest members of the macropod (or “big foot”) family, which also includes kangaroos and wallabies. The quokka clan makes its home in swamps and scrublands, tunneling through the brush to create shelters and hideouts and emerging at night to find food.

They’re the only land mammal on Rottnest Island, and have become something of a tourist attraction. Quokkas were first described by Dutch sea captain Willem de Vlamingh, who reported finding “a kind of rat as big as a cat.” The squeamish seaman named the quokkas’ island Ratte nest (“rat’s nest”), then sailed away, presumably toward more genteel wildlife.

As for pronunciation, dictionaries offer two options. North Americans usually pronounce it kwo-ka (rhymes with mocha), and everyone else says kwah-ka (rhymes with wokka wokka). It’s really up to you. Quokkas don’t care.

2. The quokka will cut you.

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The “world’s happiest animal” is not all sunshine and lollipops. You may not want to hear this, but it’s true. A quokka’s big feet are tipped with very sharp claws. Like much of Australia’s wildlife, the quokka will f*** you up if you give it the opportunity.

Journalist Kenneth Cook learned this the hard way when he tried to befriend a quokka along a dirt road. Cook noted the animal’s “small, mean mouth,” but decided it was probably too small to do much damage. “It was a malicious-looking beast,” he wrote in his 1987 book Wombat Revenge, but he wasn’t afraid. He offered the little animal a piece of apple, which the quokka spat out, and a crumb of gorgonzola cheese. The quokka popped the gorgonzola into its mouth, chewed, and then, Cook says, “fell down in a dead faint.”

Convinced he’d just poisoned the creature and determined to save it, Cook zipped the quokka’s body into his backpack, left a little room for air, swung the pack onto his back, and pedaled his bicycle frantically down the road to find help. After a few minutes of bumping along at breakneck speed, the quokka began to revive, and blearily climbed out of the backpack, claws first.

Afraid to turn around in case he lost control of his bike, Cook sped onward. The quokka grabbed his neck and began shrieking in his ear. The bike kept going. The shrieking quokka sank its teeth into Cook’s earlobe and hung there, dead weight, like a large, furry earring. Disoriented, the journalist steered his bike off a cliff and into the ocean. Surfacing, he looked around and found the quokka standing on the shore, glaring at him and snarling.

The story seems incredible, but Cook is far from the winsome creature’s only victim. Teddy-bear ears and doe eyes aside, these animals are ready, willing, and able to fend for themselves. Each year, the Rottnest Island infirmary treats dozens of patients—mostly children—for quokka bites.

Among their own kind, quokkas are primarily a peaceful bunch. Males don’t fight over choice females, food, or water, although they will occasionally scrap over a nice, shady napping spot.

3. The Quokka uses humans.

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Quokkas, who are inquisitive, appealing, and fearless, have adapted to human presence in their environment in admirable fashion. Campsites and condos are all fair game for hungry quokkas, who have become notorious for raiding local homes in search of late-night snacks. Quokka settlements have sprung up around youth hostels and tourist sites—places, in other words, where the canny animals are assured of an easy meal. Cognitive science researchers like Arizona State University’s Clive Wynne have turned the tables on the quokkas by setting up shop in these same sites, knowing the wild animals will play nice.

On Rottnest Island, the inquisitive critters have made themselves something of a nuisance for business owners. “They wander down the streets and into cafes and restaurants,” Senior Constable Michael Wear told the Daily Telegraph.

They’re not just after our food, though—we also make good entertainment. While tracking a female quokka named Imelda through the brush at night, Bangor University conservationist Matt Hayward realized he was being followed. “I heard footsteps approaching,” he told National Wildlife. Each time Hayward turned off his tracking equipment, the footsteps ceased. Just as his terror reached its peak, he said, “a little head poked out from behind a bush.” His stalker? Imelda.

4. The quokka is kind of a badass.

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Think of the quokka as the panda’s polar opposite. Where the panda seems determined to erase its own species from the face of the Earth, the quokka is a gritty survivor, ready to do anything it takes to stick around.

For example: Pandas spend between 10 and 16 hours each day foraging and eating. Why? Because bamboo—which makes up 99 percent of their diet—has almost no nutritional content. Quokkas, on the other hand, divide their time between eating leaves and grasses and snoozing in the shade. When water is scarce, quokkas chow down on water-storing succulents. When the good leaves are hard to reach, they climb trees. The quokka does not settle for useless food.

Both pandas and quokkas are prone to offing their own offspring, but there’s a crucial difference: intention (or lack thereof, in the panda’s case). When pursued by a predator, a fleeing quokka mom will eject her baby from her pouch. Thusly launched, Baby Q flails about on the ground, making weird hissing noises and attracting the predator’s attention while Mama Quokka escapes to live another day. She can, and will, reproduce again. It’s a stone-cold strategy, but it works.

Panda cubs, those rare and precious million-dollar babies, have been killed when their own mothers accidentally sat on them.

5. No, you can't keep a quokka as a pet.

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Sorry. Wild quokka populations are declining as invasive predators like foxes and cats move into quokka territory. They need to stay in the wild. You can’t have one.

And don’t try to smuggle them, or snuggle them, either: Rottnest Island authorities will slap a $300 fine on anyone caught touching a quokka. Whether the fine is intended to protect the quokkas or their would-be human scratching posts is unclear.

6. Yes, quokkas do smile—but we don't know if they're happy.

It’s fierce, fearless, and totes adorbs, but is it happy?

Nobody knows. Clive Wynne’s cognitive experiments disproved the long-held assumption that quokkas were “really, really dumb”—an assumption, he said, he found even in scientific literature. The smiley little guys don’t “have any magical cognitive abilities,” he says, “but they’re not stupid. They have the skills they need—honed by evolution over millions of years—to thrive in their natural environment.”

So why are they smiling? Consider Bitchy Resting Face, a condition suffered by several Hollywood A-listers. Consider the great white shark, with its face permanently stretched into a dopey grin. The quokka’s Mona Lisa smile, says Clive Wynne, is “an accident of evolution.”

He’s the expert, so we’ll take him at his word. But if we were tenacious, tiny furballs with anime-cute faces and vicious claws, we’d be smiling, too.

This story has been updated.