Happy birthday, Fiona the hippo! (Now please don't kill anyone)

Fiona, the world's most famous hippopotamus, turned 1 on Wednesday. The birthday celebration, which consisted of her munching on a tower of tropical fruits at her home in the Cincinnati Zoo & Botanical Garden, was broadcast on Facebook Live and watched by thousands of fans who called her "sweetie," sent virtual kisses and told her they loved her.

This was no ordinary milestone. Born six weeks early at just 29 pounds, Fiona survived against all odds. Zoo caretakers hand-fed her infant hippo formula, warmed her with blankets and embraces, and massaged her gums when they were sore. And because they did all this on camera online, the pudgy-wudgy hippo, who seemed to smile through the drama, became a sensation. Playing cards, magnets, tote bags and cutting boards bearing her likeness were made. Ice cream and beer were named after her. Obsessives monitored her like she was their own baby. Even as Fiona expanded, she looked adorable and squishy enough to hug.

Amid all this heart-melting cuteness, the question from one viewer of Wednesday's Facebook party felt a bit abrupt: "When," this person asked, "will she become dangerous to her caretakers?"

The answer: Fiona already is. Very much so.

"She could knock us over and take us down with no problem," Christina Gorsuch, the zoo's curator of mammals, said in an interview this week.

The reality is that Fiona is a hippo, and hippos can be very deadly beasts. While this one is only about a fifth the size she will be as an adult, at 650 pounds she's as heavy as a bulky Harley-Davidson or a couple of refrigerators. Her heft is one reason Fiona will henceforth be more of a "full-time hippo," as opposed to a "part-time hippo, part-time human," Gorsuch has said.

In practical terms, full-time hippo-ing at a zoo means that Fiona can now be handled only through metal barriers. Keepers who once cradled her 24 hours a day completely stopped sharing space with her about a month ago, Gorsuch said. Bottle-feeding ended weeks ago; Fiona now gets hay, grains and produce. She's being trained – to swallow big pills when needed, to have blood drawn from her tail, and to paint hippo "kisses" with her lips – but that's also through barriers.

Fiona has taken this separation in stride, as have her smitten keepers, for the most part. "It's a little sad to see it over," but Fiona "can very easily hurt somebody, even without meaning to," Gorsuch said.

But hippos can also mean to, as Rebecca Lewison has seen with her own eyes. Lewison, a conservation ecologist at San Diego State University, was researching hippos in Tanzania several years ago when she saw a female anxiously nudging a calf that was stuck in the mud. Pursuing them was a male that Lewison watched "grab [the baby] and chuck it up, then chomp it" with its enormous teeth, known as tusks. Lewison inspected the impaled carcass and went on to publish a paper on this never-before-documented hippo infanticide, which she theorized is driven by a territorial male's desire to mate with a nursing female.

Being a full-time hippo in the wild involves a lot of time in the water by day, Lewison said. After sundown it turns into a "lawn mower" as groups "walk and chew, and walk and chew, and walk and chew" on established trails to and from grazing areas. That said, although they are herbivores, hippos have been documented dining on carcasses of peers and other animals.

Hippos don't consume humans, but regular run-ins with people have earned them a reputation as one of the world's deadliest animals. Lewison said no good data exist to verify that, but there's no doubt human-hippo conflict is on the rise, mostly because of hippo habitat loss, and deaths occur when hippos perceive their space or resources to be threatened. In recent months, according to news reports, hippos have killed a Zimbabwean man crossing into South Africa and a Michigan woman on safari in Tanzania.

"They, like, hole-punch you," Lewison said when asked how a hippo can kill a human. "I study hippos, I love them, but I am not going on any of those safaris that go down the Zambezi" river, in Zambia, where loads of hippos live. "They feel threatened, and what do they do? They knock your boat over, and they use the tool that they have, which is their mouth."

Lewison has not followed Fiona, but she said she didn't see a big downside to her anthropomorphic image as an animal more likely to wear a tutu than wield her tusks. She also didn't see a big upside for wild hippos. The world has plenty of "hippo enthusiasm," Lewison said, though it hasn't translated into support for hippo conservation.

"For some reason, it's hard for people to connect with them in a way that doesn't seem to be as hard with elephants or other animals," said Lewison, who chairs the International Union for Conservation of Nature's hippo specialist group. "They really do like zoo hippos."

Gorsuch, for her part, said she thinks Fiona is an excellent hippo ambassador who's teaching her followers lots about her species.

Besides, Fiona would never hole-punch anyone, would she?

Probably not, actually. There are the physical barriers, of course. But Gorsuch said zoo hippos also tend not to get super aggressive, because they've got plenty of food and water, and they're the masters of their territory. That doesn't mean the Cincinnati zoo's staffers have any intention of indulging in even the briefest of hugs from here on out.

"We just are very respectful of their size and what they can do with their size," Gorsuch said of Fiona and her 3,000-pound mother, Bibi. Also of their teeth, which the toddler Fiona is cutting now. "When she has full-grown hippo tusks, we're not going to be sticking our hands in her mouth."