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. 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]
