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[♪ INTRO]

We humans like to think  we're pretty good swimmers.

But… any prowess we have is learned.

Most other mammals don't need lessons!  For them, swimming is instinctual.

And that includes the mammals you'd least expect

to be at home in the water… like… moose.

Moose are massive deer —

we're talking up to 600 kilos sitting  atop four comically thin legs.

So, you might not think they'd be great swimmers.

But in summer and fall,  they're often found in water.

And they're not just dipping their hooves.

Moose will fully submerge themselves  and paddle up to 20 kilometers.

During this, their heads bob  in and out of the water —

which you might think would  lead to some serious nasal burn.

Luckily for them, their long,  flappy snoots act like a valve

to keep water from getting in their nostrils.

Now, at first, some biologists thought that

these aquatic exploits were a way of cooling off.

After all, that thick fur jacket  they wear is better for keeping cozy

in those minus -30 degree winters  than it is keeping cool in summer.

But then, they realized the animals  had an even better reason to swim.

Studies of their diets revealed that they  pick plants based on how salty they are.

And the plants that have the most  salt — like pondweed and bur-reed —

are often found in or under water!

One moose that researchers  observed even had a nifty trick

for feeding in the shallows: it used its  powerful nose to blow away the water first.

Though, they'll also dive several  meters down, if they have to.

They're so keen on salt because  it's an essential nutrient

that's somewhat lacking in land plants.

And without it, they can't  grow those impressive antlers.

There might also be other reasons  they spend so much time in water,

like avoiding mosquitos.  Or escaping hungry wolves.

But whatever the motivation for  swimming, they sure seem to enjoy it!

Moose aren't the only large  animals who are good at paddling.

Elephants can swim long distances  with a kind of lunging-style,

sticking their trunks out above the  water and using them like snorkels.

Now, at first glance you might think  that elephants are too big to float.

So did scientists.

But, it turns out their size actually helps them.

See, objects float because the downward  pressure from the weight of the object

is less than the pressure of the water  pushing upwards. That's buoyancy.

And although elephants are  heavy, they're also wide.

So, their bodies displace enough  water to counteract their weight —

and voila, they float.

They also have sizable lungs, so swimming  probably doesn't tire them out much.

And all those plants they eat  make gas in their stomachs,

kind of inflating them like a big balloon.

Oh, and their skull bones have lots of  holes in them, kind of like a sponge—

which is probably to make them slightly  less heavy, but it also gives them buoyancy.

Researchers think that  elephants' swimming abilities

might have helped their ancestors  colonize offshore islands.

And fossil evidence shows that  ancient island-dwelling elephants

are related to mainland ones.

So swimming could have helped  elephants find new food sources

and reduce competition between individuals.

Nowadays, elephants might swim  to keep their huge bodies cool —

although no one has tested  this idea scientifically yet.

Armadillos look more like living  tanks than agile water-babies.

Still, they're innately  better swimmers than we are.

They'll doggy-paddle their way through  the water, with their ears lying flat,

poking their little noses out  every now and again for air.

Actually, it's kind of a big  part of their whole swim game.

They're naturally negatively  buoyant, meaning they sink in water.

And it seems like they sometimes roll with that,

and just run their way along the  bottom if it's shallow enough.

At least, that's what one armadillo did

when a researcher kept throwing into the water.

But for deeper crossings, nine-banded armadillos

have been seen gulping large amounts of air.

And researchers think that's to inflate  their stomach and small intestine

to make them more buoyant.

Some of the first observations of  armadillos swimming date back to the 1930s,

where biologists saw that they  could swim about 50 meters

after being tossed out from shore.

And in 1994, Brazilian fishers  found a female yellow armadillo

swimming along about 50 meters  off the island of Cajual.

The animal might have been making  the 500-meter swim from the mainland

to reach the rich food resources on  the island—things like crabs, tubers,

or even garbage from the local lodge.

Or, she may have been seeking refuge

from the mainland predators  that don't exist there.

The same theory might explain how armadillos  made it from Missouri to Illinois —

by paddling between chunks of land  to cross the Mississippi River.

Right now though, scientists only  have a few observations to go by,

so it's hard to know how or why  armadillos started swimming,

or whether it's a really common behavior.

But they definitely seem to  know how to, if they need to!

In north-western parts of India, you can witness

an unexpected sight: herds of camels swimming.

These are the Kharai — the only  camel breed that regularly swims,

though others are perfectly capable.

Like moose, they paddle more than 3  kilometers in search of their favorite fare.

In fact, it's been reported that their  name comes from the local word for salty or

saline, since they love eating  salty plants like mangroves.

Nowadays, these special camels persist

because locals breed them as  draft animals and for their milk.

But around 2,000 years ago swimming  camels may have been a lot more common.

According to fossil and DNA evidence, it  may have been our domestication efforts

that made camels into the  desert creatures we know today.

Before that, camels were probably  isolated to mangrove regions

on the coast of Arabia, where  swimming would have come in handy.

Sadly, the Kharai camel's mangrove  habitat is now being depleted.

Camel numbers have dropped from  around 10,000 to less than half that.

And experts say that if their  habitat isn't protected,

they may be the last truly  swimming camels we ever see.

A kangaroo's powerful legs are great  for hopping around the outback.

But they also seem to be quite useful  underwater, in a totally different way.

Even though they make the  animals quite bottom-heavy,

those chunky hind legs allow them  to tread water and stay buoyant.

And they do that by alternating their  kicks — kind of how we humans do.

Which is notable mostly because, on  land, they move their legs together.

They seem to just naturally know to switch  that up when they get in over their heads!

We know all this because some researchers  thought “I wonder what happens when I

throw this in a pool.” Which  is super rude, if you ask me.

But, this experiment also showed  they can get forward drive

from a combination of their front  limbs doing a kind of powerstroke,

and their tails swishing from  side to side like a fish.

With all those parts working together in a  coordinated way, they can apparently swim

at a speed of about a meter a second,  roughly half the pace of the fastest humans.

Which, considering their lack of  training, is pretty impressive.

Now, no one is really sure why kangaroos  have this innate swimming ability.

Aside from one research report from the 1970s,

there haven't been many  scientific studies on the matter.

Researchers have spotted kangaroos  swimming in flooded rivers

to escape dogs chasing them — so it  could be a way to flee from predators.

Or, like the armadillos, kangaroos  may have relied on swimming

to cross rivers or reach offshore islands.

They've been spotted swimming  up to 3 kilometers at a time,

so they could cross decently  large bodies of water.

There's a fascinating account  by naturalists in the 1920s

of an animal swimming across rivers in  Guyana, driven by some “powerful instinct”.

This animal? An unassuming three-toed sloth.

Yes, despite their reputation for  living the slow life in trees,

sloths are adept swimmers.

Both two- and three-toed sloths can swim

and they seem to be better at moving  through water than across land.

They can swim three times  faster than they can walk!

That's mostly thanks to their long arms.

You see, once in the water, the  animals spread their back legs out

for balance and buoyancy — kind  of like a stabilizer on a canoe.

Though, it's not just their  legs helping them float.

Sloths are also slow digesters, so  gas builds up in their stomachs,

turning their bodies into makeshift life vests.

Ultimately, this means that, most of the  time, they swim with their heads above water.

Though, they're more than capable  of holding their breath if needed.

Experiments done in the lab found that

sloths can go without oxygen  for more than 20 minutes.

Which, for the record, is longer  than a bottlenose dolphin!

They might have inherited these excellent  water skills from their ancestors.

Some ancient sloths were actually semi-aquatic!

Instead of feeding on leaves  in trees, they ate seagrass.

But now, sloths likely use their  swimming abilities to get around.

After all, their jungle habitats  are full of rivers and lagoons

that they may need to navigate  to get to food or other sloths.

And if your mate was on the other side of a river,

you'd probably swim like you're being  'driven by a powerful instinct', too!

If you've ever checked out primates at a zoo,

you might have noticed their enclosures  tend to have a common feature: a moat.

That's because, whether we're talking  lemurs or chimpanzees, primates generally

aren't known for navigating deep  water… at least, not without training.

All that time spent in trees probably  meant there was little reason

for our evolutionary cousins  to be naturally good swimmers.

But there's at least one major exception  to this...the proboscis monkey.

They've been seen diving into  rivers from high up in the trees,

and swimming, totally submerged,  for nearly half an hour!

Their fondness for water is likely a clever way

to dodge predators like clouded  leopards that hunt them in the trees.

One study even suggested that proboscis monkeys

set up their sleeping sites near narrow  parts of the river so they can leap in

and escape more quickly if they need to.

And they have a strategy for water-dwelling  dangers like crocodiles, too.

They basically do cannonballs into the water!

Experts think that makes sure their  splash is loud and big — enough so that it

temporarily scares off anyone lurking  below while they swim to safety.

They actually have several features  that facilitate their aquatic exploits.

For example, they have a bit  of webbing at the base of

some of their fingers and toes,  which adds power to their strokes.

Though, this also likely helps them  wade through muddy mangrove soil,

which may explain how it arose.

Some primatologists think that  proboscis monkeys ended up

confined to habitats close to  the water because inland plants

don't always give them enough  salt or other nutrients.

And, hey, when you're that close to  water, it pays to know how to swim!

So yeah, weird as it might seem,

basically all other mammals put our  innate swimming ability to shame.

Of course, they need their swimming  prowesses — whether it's to escape predators,

seek out food or friends, or  find totally new places to live.

So next time you're showing off your front  crawl or butterfly stroke in the pool,

maybe channel your inner  moose, camel, or even sloth.

And I know the perfect music  to blast while you paddle about

pondering the elegance of swimming  sloths: the Music for Scientists album,

written and recorded by Patrick Olson!

For instance, one song on the  album is called 'The Idea',

and it touches on how difficult  it is to form correct ideas —

because for every right answer, there  are an infinite number of wrong ones.

And the music video for it is breathtaking.

It was created by taking over  15,000 photos of three paintings,

which were then brought to  life using machine learning!

If you think you'd enjoy this, you can click  the link in the description to check it out.

[♪ OUTRO]