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