Speaker 1: Welcome to brain Stuff, a production of I Heart Radio,
Speaker 1: Hey brain Stuff, Lauren Vogelbaum. Here in the eucalyptus forests
Speaker 1: of Australia, you'll find the world's remaining wild koalas eating
Speaker 1: leaves and sleeping. That's pretty much all these marsupials do.
Speaker 1: They sleep for up to twenty hours a day, cradled
Speaker 1: in eucalyptus branches, wake up to eat some leaves, and
Speaker 1: go back to snoozing on a full stomach. It's a
Speaker 1: lazy life that revolves around a monotonous diet, and koalas
Speaker 1: are perfectly adapted to it. Eucalyptus leaves have very little
Speaker 1: nutritional value, provide almost no energy in the form of calories,
Speaker 1: are hard to digest, and are poisonous to almost every
Speaker 1: mammal besides the koala. Perhaps, needless to say, kuala's face
Speaker 1: little competition for their favorite food source. They consume up
Speaker 1: to one and a half pounds or six hundred and
Speaker 1: eighty grams of leaves in a single day. That's about
Speaker 1: a thousand leaves. They spend pretty much all of the
Speaker 1: energy they get from the leaves on chewing and digesting them.
Speaker 1: Eucalyptus leaves are so fibrous that most animals wouldn't go
Speaker 1: near them even if they were safe to eat. So
Speaker 1: how can koala's eat eucalyptus. Koalas have cheek teeth that
Speaker 1: grind up the tough leaves, and their other teeth are
Speaker 1: spaced specifically to slice the leaves into smaller pieces that
Speaker 1: they can swallow. But the most important part happens inside
Speaker 1: their bodies when their eucalyptus friendly digestive system takes over.
Speaker 1: Just as we humans all have a microbiome inside our
Speaker 1: guts to help us digest our food, Aquala's digestive tract
Speaker 1: is full of different types of bacteria that make eucalyptus
Speaker 1: both safe and somewhat digestible. A koala has an organ
Speaker 1: called a secum. Humans actually have it too, but a
Speaker 1: koala is much bigger. The secum contains bacteria that break
Speaker 1: down the eucalyptus fibers. This makes it so that at
Speaker 1: least some of the leaf about can be digested that
Speaker 1: is converted into calories for nutrition and energy. There are
Speaker 1: other digestive trick is bacterium that neutralizes the toxins in
Speaker 1: eucalyptus oil mostly sine, all the poisonous component that makes
Speaker 1: the leaves unsafe for most mammals. Of the roughly five
Speaker 1: hundred types of eucalyptus trees out there, kualas only go
Speaker 1: for a couple dozen types, and of those, any particular
Speaker 1: group of koalas will have a few favorites. Eating the
Speaker 1: same few types of eucalyptus all the time probably helps
Speaker 1: kuala's learn the scent of a leaf that has a
Speaker 1: different toxic substance in it, called prussic acid. Prussic acid
Speaker 1: is toxic even to koala's, so they have to be
Speaker 1: very careful not to eat those leaves. It's not hard
Speaker 1: to see why a koala might smell like eucalyptus, since
Speaker 1: it's pretty much all they eat, and this means that
Speaker 1: koalas hardly ever have to leave the trees, so they're
Speaker 1: out of reach from the countless predators who would find
Speaker 1: the twenty five pound or about eleven kilo slow moveing
Speaker 1: marsupial and easy target. It also means they can sometimes
Speaker 1: smell like cough drops only sometimes, though it's mostly the
Speaker 1: young koalas that give off a slight eucalyptus scent. Adult
Speaker 1: kuala is apparently smell more like a mixture of urine
Speaker 1: and kuala mating musk, according to the Australian Kuala Foundation.
Speaker 1: But here we come to an interesting question. If eucalyptus
Speaker 1: oil is toxic, how can it be used in cough drops.
Speaker 1: As with most substances, it's all about moderation. What's toxic
Speaker 1: at high doses can be neutral or beneficial in small amounts.
Speaker 1: Kualas eat lots of different types of eucalyptus leaves, some
Speaker 1: of which contain tremendous amounts of toxins like seniol. Oil
Speaker 1: from eucalyptus leaves can be up to seni al. Most
Speaker 1: herbal remedies containing eucalyptus, which date back at least hundreds
Speaker 1: of years in the aboriginal cultures of Australia, come from
Speaker 1: the blue gum species. The oil in blue gum leaves
Speaker 1: contains much less senniol, as little as four percent by volume.
Speaker 1: Eucalyptus oil finds its way into cough drops mostly because
Speaker 1: of its anti inflammatory properties, which are attributed to the seniol.
Speaker 1: Eucalyptus also has both antimicrobial and antibacterial properties. It's used
Speaker 1: in herbal medicine to treat everything from the common cold
Speaker 1: to fungal infections to bronchitis. With all of eucalyptus oils
Speaker 1: medicinal applications, you'd think koalas would be protected against just
Speaker 1: about every nuisance out there, but no, they're still subject
Speaker 1: to their own health concerns. Eucalyptus oils may protect eucalyptus
Speaker 1: trees from bugs and parasites, but kualas have as many
Speaker 1: ticks as the next marsupial and they also have the
Speaker 1: sexually transmitted disease chlamydia in strangely large numbers. Aside from that, though,
Speaker 1: the biggest threads to koalas are domestic dogs, speeding cars,
Speaker 1: and of course, greenhouse gases and increasing carbon dioxide maybe
Speaker 1: sapping what few nutrients Eucalyptus ly eaves have to offer,
Speaker 1: and in the early nineteen hundreds, kouala fur was all
Speaker 1: the rage. Eight million kualas were killed between nineteen nineteen
Speaker 1: and nineteen twenty four alone. In the late nineteen twenties,
Speaker 1: countries started protecting koalas, which are now considered a vulnerable species.
Speaker 1: There are only about a hundred thousand left in the wild.
Speaker 1: Today's episode is based on the article du Kouala smell
Speaker 1: at Cough drops on house to works dot com, written
Speaker 1: by Julia Layton. Brainstuff is production of by Heart Radio
Speaker 1: in partnership with how stuff works dot Com and is
Speaker 1: produced by Tyler Play four more podcasts from my heart Radio.
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