This episode is brought to you by the Music for Scientists album,
now available on all streaming services.
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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.
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