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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]