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The definition of a carnivore is simple enough.
Any animal that eats other animals gets to wear that title.
And many of these creatures are part of the order Carnivora:
a group of mammals with a shared lineage that mainly hunt their food.
Carnivora literally means meat eaters.
But… despite their name, not all Carnivora eat meat!
For instance, pandas are in this order,
even though they basically eat bamboo all day.
But as weird as it sounds, pandas actually have a lot in common
with their meat-eating carnivore cousins.
And scientists only recently figured out why.
Now, all creatures in the order Carnivora share a few key traits:
sharp teeth, claws, and a gut full of bacteria that can digest meat.
Pandas clearly have the teeth and the claws.
And surprisingly enough, researchers recently found
that they have the gut bacteria of a meat-eater too.
In fact, their guts look way more like those of meat-eaters than vegetarians.
Plant-eaters often have enlarged small intestines to slow the passage of food,
giving their gut bacteria more time to digest all the fibrous material they eat.
Meat is less fibrous, so meat-eaters don’t need
as complex of a gut to break down their food.
And despite the fact that pandas eat up to a third of their weight in bamboo
each day, panda guts are short, similar to those of meat-eaters.
Pandas did evolve from meat-eating ancestors.
And even now, giant pandas will occasionally deviate from their vegetarian habits,
snacking on things like insects, bird eggs, and even small mammals.
But at most, this makes up about 1% of a panda’s diet.
So, scientists were curious why these animals
didn’t evolve digestive systems better suited to eating plants.
Finally, in a study published in 2019, researchers found that the answer
has to do with bamboo, which pandas started eating when they split off
from their carnivore ancestors millions of years ago.
The authors of the study took a look at the nutrient profile of this plant.
And they discovered that the parts of bamboo preferred by pandas
are high in protein and low in easily digestible carbohydrates…
more like meat than other plants.
So pandas’ ancestral gut microbes were actually pretty useful
for digesting this particular plant.
And it turns out that, while most plant-eaters’ diets are relatively low in protein,
pandas seek out a high-protein diet, much like meat-eaters.
The same team of researchers figured this out
by tracking wild giant pandas as they ate.
They noticed that these animals migrate long distances to munch on shoots
and leaves of two different bamboo species that grow at different elevations.
Every year, the pandas start out by eating the leaves on the bamboo
at the lower elevation.
Then they eat the shoots of the same plants,
which started growing later in the spring.
From there, they move upward to the higher-altitude species,
eating first the shoots, then the leaves.
Then they head back down again to start all over.
By analyzing what the pandas were eating, the researchers determined that the
pandas were selectively eating the parts of bamboo that had the most protein…
and also the least fiber.
Plant-eating animals are typically good at digesting fiber,
thanks to their gut microbes and long small intestines,
but since pandas have the guts of meat eaters, it’s much harder for them.
They can’t easily digest the more fibrous,
cellulose-rich parts of bamboo, so they seek out the shoots and the leaves.
Pandas’ diet can help explain how they evolved
from meat-eaters to vegetarians millions of years ago.
By selectively eating the high-protein parts of the bamboo, ancestral pandas could
transition to being almost solely vegetarians without a drastic anatomical overhaul.
And that’s why today we are left with this surprising member of the order Carnivora,
munching bamboo despite being built like a carnivore.
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