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  • This episode is brought to you by  the Music for Scientists album,

  • now available on all streaming services.

  • [♪ INTRO]

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

  • Butany prowess we have is learned.

  • Most other mammals don't need lessonsFor them, swimming is instinctual.

  • And that includes the mammals you'd least expect

  • to be at home in the waterlikemoose.

  • 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 fallthey'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 longflappy 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  saltlike 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 mosquitosOr 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 islandthings 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 Kharaithe only  camel breed that regularly swims,

  • though others are perfectly capable.

  • Like moose, they paddle more thankilometers 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  kickskind 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 incoordinated way, they can apparently swim

  • at a speed of about a meter a secondroughly 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 themso 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 somepowerful 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 buoyancykind  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  waterat 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 submergedfor 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 bigenough 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 toeswhich 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  prowesseswhether 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]

This episode is brought to you by  the Music for Scientists album,

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