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Bones are hard to digest and can be downright dangerous to eat, but some animals have evolved pretty bizarre adaptations to accommodate their crunchy, splintery diets.

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Bones. Between bone broth and bone marrow, they’re all the rage among fans of superfoods although their health  benefits are dubious at best.

But osteophagia — a.k.a  eating bones — is nothing new. For millions of years, a variety  of creatures have savored the lip-smacking taste of skeletons. And that’s kind of as hardcore as it sounds.

Bones are difficult to digest  and downright dangerous to eat. They’re a choking hazard, and they can tear the esophagus  and poke through intestines. But some animals have evolved pretty  bizarre adaptations to accommodate their crunchy, splintery diets.

Like, an extra stomach or skin that oozes acid.   If you’ve ever been on a safari, you  may have witnessed a strange sight: a giraffe with a leg bone or a rib  cage sticking out of its mouth. But giraffes are famous for being herbivores.   I mean, that ridiculously long neck  is to help them eat leaves off trees. And yet, there they are, just casually  noshing on some buffalo bones.

Turns out a lot of vegetarian animals  cheat on their plant-based diets. Osteophagia has been observed in  wildebeest, deer, camels, caribou, porcupines, sheep, and giraffes, which also  gnaw on elephant tusks, of all things. These animals mainly gnaw on  bones, breaking off tiny pieces.

And although we need more research,   scientists think they’re doing it because  bones are rich in calcium and phosphorus nutrients that are critical in  the formation of, well, bones. They’re also vital for the  nervous system, energy production, lactation, and lots of other  essential bodily functions. But in many parts of the world, the  vegetation is low in phosphorus, so some herbivores might not be  getting as much as they need.

Plus, sometimes animals need extra nutrients, like when they’re growing  antlers or are pregnant. So even though they’re mostly  vegetarian, giraffes and other herbivores might chew on bones to get  the minerals they require. Hey, no judgment here.

Next, some birds swallow their prey whole, but that doesn’t always mean they  can digest the whole animal. For example, owls, hawks, and  herons can’t digest bones, teeth, feathers or fur, so they regurgitate  all of that up in bony, fuzzy blobs. Other feathered friends have  a less nauseating solution.

And for pelicans, which swallow entire  fish, that strategy is a third stomach. Like most birds, pelicans have a  stomach that secretes gastric juices and fires up the digestion process. Also like most birds, pelicans have  a second stomach called a gizzard.

It’s muscular and contains rocks  that the bird has purposely swallowed to help grind up its food. Usually, the gizzard feeds into the intestines  through a sphincter called a pylorus. But in pelicans, the pylorus  is a super-muscular chamber called a pyloric stomach.

And scientists believe this third stomach  filters the bones and prevents them from making it into the intestines, where they  might poke through and cause damage. Some other fish-eating birds  also have a third stomach. But this extra organ isn’t the  only way birds can eat bones.   When it comes to scarfing down skeletons, it’s tough to beat the bearded vulture.  Bones make up 70 to 90% of its diet.

These birds are intense. They’re also known as lammergeiers,  which means “lamb vultures” in German because legend has it they pick  up sheep and fly off with them. Although that’s probably not true.

But we do know that these vultures have  an interesting way of eating bones:. When they come across an animal carcass, they can swallow the small bones whole. The larger bones pose more of a challenge, though.

So they grab them, fly high in the  air, and drop the bones onto rocks, smashing them to smithereens. Then the vultures can eat the smaller  pieces and the fatty marrow inside. Surprisingly, unlike many other birds,  bearded vultures don’t have a gizzard.

Which you’d think would be  handy for pulverizing bones. Instead, they have stomach  acid with a pH of one or less close to pure hydrochloric acid. They simply dissolve the bones in their bodies.

Hyenas also eat a lot of bones and marrow. But as you may have noticed, they can’t fly, which means no using gravity  to break bones apart. Instead, they use another  strategy for smashing skeletons:.

They evolved bone-crushing jaws. The ability to crack open large bones  with your mouth is extremely rare. In fact, hyenas are the only  animals alive today that can do it.

Part of their secret is their  unusually shaped faces. Hyenas have huge jaw muscles that  attach to extra-large cheekbones and to a structure on top of their  skull called a sagittal crest. It basically looks like a mohawk made of skull.

This bone mohawk allows them to  attach more muscles to their head, plus give those muscles more leverage. They also have robust teeth  with super-strong enamel. All the better to bite into  your skeleton with, my dear.

All three species of hyenas can  crack open bones with their mouths, but the spotted hyena is particularly brawny:. It can crush the leg bones of a giraffe. In fact, hyenas eat so much  bone and digest it so thoroughly that their dried poop is usually bright white.   Speaking of hyena poop… It’s what’s for  dinner — if you’re a leopard tortoise.

Remember we said bones are high in calcium? Well, leopard tortoises need lots  of calcium to build their shells. So they chew on bones, like  some other herbivores.

But that doesn’t always fulfill their needs. So they also eat hyena feces, because  it’s so full of digested bones. Leopard tortoises aren’t the  only species that does this.

Desert tortoises eat bony vulture poop, which contains plenty of leftover  calcium and phosphorous. But they don’t stop there. Desert tortoises also eat the bones  and shells of other desert tortoises.

They’ve even been observed climbing  on top of dead tortoises’ shells, raising themselves high up on their  legs and then pulling their legs inside their shells so they drop onto  the dead tortoise shell and break it. Then, they eat some of the broken shell pieces. Will animals stop at nothing  to get their bony treats?

Well… just wait. Deep in the ocean live feather-shaped  worms that have no mouths or intestines. And they still manage to digest  the entire skeletons of fish, turtles, and even whales.

They’re called osedax worms. That’s Latin for “bone-eating.”

When a sea creature dies  and sinks to the sea floor, various animals eat the carcass  until it’s not much more than bones. That’s when osedax worms come onto the scene.

They drill a root system into the animal’s bones and then excrete acid from their  skin that dissolves the bones. Next, bacteria living inside the worms  digest the proteins and fats in the bones. Then somehow, the bacteria  transfer the nutrients to the worms scientists aren’t exactly sure how.

Interestingly, in most osedax  species, only female worms eat bones. And the reason has to do with their  outrageous reproductive methods.   Apparently, dating on the bottom of the  ocean is even harder than it is online. So, eligible osedax ladies  have an unusual strategy.

The females are anywhere from 1500 to  100,000 times bigger than the males.   So the females just store the males  inside their bodies until they need them. They accumulate more and  more males as they get older sometimes as many as 600 of them. And with a group that big, no wonder  they’re on the hunt for nutrients.

If you think osedax worms might be the  most extreme example of a small critter eating a larger animal’s bones,  may I present another contender…  . Over the past couple of decades, more  and more scientists have been reporting on an annoying phenomenon in  their dinosaur bone fossils:. They have bites taken out of them.

In 2008, researchers from  Brigham Young University in Utah examined more than 5000 dinosaur  bones and discovered that approximately one-eighth of them had  been partially eaten by insects. The bones had telltale boring  marks, pits, and channels in them. The main culprit in this batch of dino bones was a family of beetles called dermestids.

Paleontologists think these  beetles started infesting the bones only a few days or weeks  after the dinosaurs died. Once the dino carcass had  been devoured by scavengers, the beetles may have laid their  eggs on the skeletal remains. Then, their larvae hatched and  munched on the remaining flesh and some of the bone.

In other cases, scientists think  insects ate the dinosaur bones long after they were buried under sediment. Paleontologists have found evidence  that insects bored into dinosaur bones around 190 million years ago. But they generally don’t know what kinds  of insects were involved back then, let alone how and why they  were eating dinosaur bones.

One hypothesis is that the insects  were hungry for the nitrogen in the decaying carcasses, because  nitrogen is scarce in a lot of places. But there’s not much evidence for that yet, so we’ll need more research to know for sure. Thankfully, scientists are  dedicated to their research, as you’ll see in what may be the  quirkiest item on this list.   Right about now, you might be asking the question:.

Can humans digest whole bones? Well, in 1991, two anthropologists  set out to answer that question in a study that gives new meaning to  the phrase “the taming of the shrew.” First, they captured a shrew — a mammal  that looks like a long-nosed mouse. They skinned it, disemboweled it,  and cut it into large segments.

Then they lightly boiled it for two minutes. Next, one of the scientists  ate it without chewing. Over the next three days, he  collected all of his poop.

Then he stirred the feces in a pan of warm water and decanted it through a cheesecloth. As you do. Finally, he examined it in an electron microscope.

While some of the bones  did come out the other end, many were apparently totally  digested, including a major jawbone, many leg bones, almost all of the  toe bones, and most of the vertebrae. So there you have it. Humans can digest small bones — sort of.

To be clear, though, they’re  still a choking hazard, and they can puncture your digestive system. So it’s best to leave osteophagia to  the experts in the animal kingdom. Thanks for watching this episode of SciShow!

If you’re in the mood for  more bone-related content, you can also check out our episode about  why otters have bones in their hearts. [♩OUTRO].