If there's one thing you know about sloths,
it's that they're,
well,
slow.
But that doesn't mean they're boring.
In fact, sloths are one of the most
extreme animals on the planet,
and not just because they poop only once a week.
First of all, sloths really are extremely slow.
Their top speeds clock in at just 0.25 kph,
making them the slowest mammal on the planet.
According to zoologist Becky Cliffe,
that's because, well, sloths can't really see.
Becky Cliffe: 60 million years ago, they lost
the ability to see.
They went almost completely blind.
So, in the daytime, a sloth actually
can't see anything 'cause it's too bright.
If you can't see where you're going, you can't run around
because you're going to fall out the tree.
Narrator: Moving slowly may sound like a liability,
especially if you're nearly blind,
but being sluggish actually
comes with all kinds of benefits.
For one, they save an enormous amount of energy.
In fact, sloths use about 90%
less energy than the average mammal, which is vital,
considering their diet is a low-energy snack
consisting of leaves...with a side of leaves.
And as it turns out, being slow
also helps sloths avoid detection.
You see, sloths are so slow that predators
like jaguars and eagles,
which use movement to hunt,
can't even find them.
But some sloths take predator avoidance
to the next level.
Thanks to rare extra vertebrae in its neck,
the three-fingered sloth can turn its head 270 degrees,
which allows it to smell incoming predators
from almost any direction,
and that's especially useful when you spend
nearly all of your time motionless in a tree.
In fact, sloths sleep, mate,
and even give birth
all while hanging upside down on a branch.
And, as you might expect,
that requires some pretty extreme adaptations.
Cliffe: They've got special tendons in their hands,
which lock into place.
Narrator: And, along with their long,
hooklike fingernails, allow them to hang easily.
Cliffe: They're like a giant coat hanger.
Narrator: And to combat a rush of blood to the head,
which might be familiar if you've ever hung upside down...
Cliffe: They have special sort of valves
in their circulatory system that does actually
stop the pooling of blood in the head.
Narrator: But if you think that's extreme, consider this:
Once a week, sloths risk their lives on a daring journey
from the protective forest canopy to the ground.
Their mission?
To poop.
And it really is risky.
Cliffe: We suspect about 60% of predator-based
sloth deaths happen while they're pooping.
They literally risk their life to come down to the ground.
Narrator: So they have to make it count.
And, boy, they really do.
Sloths can lose an astonishing 30%
of their body weight each time they go.
Plus, they might get a mate out of it.
Cliffe: How do you find a mate if you're solitary
and you can't move very far?
Well, they're gonna have to use
pheromones and scent markers.
I think that coming down and leaving a little pile
at the base of your favorite trees
is sort of like a little signpost.
Narrator: But if there's one thing that really pushes
sloths over the top, it's their rough fur.
Sloth fur has its very own ecosystem.
Because they live in the rainforest,
it's often wet,
which creates the perfect environment for algae to grow
and provide sloths with green camouflage.
But it isn't just algae that calls a sloth's fur home.
You can also find beetles, cockroaches,
and a species of moth that's found nowhere else
in the world except for on a sloth.
And the sloths don't seem to mind one bit.
But that's not all.
Their fur might actually save lives.
Fungi in their fur have been shown
to fight breast cancer cells,
and they may also have properties for fighting malaria.
So, despite their slow pace,
sloths are far from boring,
and in some environments, they aren't even slow.
I mean, look at that daredevil go.