1 00:00:01,920 --> 00:00:04,320 Speaker 1: Welcome to brain Stuff, a production of I Heart Radio, 2 00:00:06,200 --> 00:00:11,160 Speaker 1: Hey brain Stuff, Lauren Vogelbaum. Here in the eucalyptus forests 3 00:00:11,200 --> 00:00:15,120 Speaker 1: of Australia, you'll find the world's remaining wild koalas eating 4 00:00:15,200 --> 00:00:18,880 Speaker 1: leaves and sleeping. That's pretty much all these marsupials do. 5 00:00:19,480 --> 00:00:22,080 Speaker 1: They sleep for up to twenty hours a day, cradled 6 00:00:22,079 --> 00:00:25,120 Speaker 1: in eucalyptus branches, wake up to eat some leaves, and 7 00:00:25,320 --> 00:00:28,400 Speaker 1: go back to snoozing on a full stomach. It's a 8 00:00:28,480 --> 00:00:32,440 Speaker 1: lazy life that revolves around a monotonous diet, and koalas 9 00:00:32,479 --> 00:00:37,000 Speaker 1: are perfectly adapted to it. Eucalyptus leaves have very little 10 00:00:37,080 --> 00:00:40,760 Speaker 1: nutritional value, provide almost no energy in the form of calories, 11 00:00:41,000 --> 00:00:44,440 Speaker 1: are hard to digest, and are poisonous to almost every 12 00:00:44,440 --> 00:00:49,280 Speaker 1: mammal besides the koala. Perhaps, needless to say, kuala's face 13 00:00:49,360 --> 00:00:53,000 Speaker 1: little competition for their favorite food source. They consume up 14 00:00:53,000 --> 00:00:55,040 Speaker 1: to one and a half pounds or six hundred and 15 00:00:55,040 --> 00:00:57,800 Speaker 1: eighty grams of leaves in a single day. That's about 16 00:00:57,800 --> 00:01:00,880 Speaker 1: a thousand leaves. They spend pretty much all of the 17 00:01:00,960 --> 00:01:04,200 Speaker 1: energy they get from the leaves on chewing and digesting them. 18 00:01:04,720 --> 00:01:07,880 Speaker 1: Eucalyptus leaves are so fibrous that most animals wouldn't go 19 00:01:07,920 --> 00:01:11,280 Speaker 1: near them even if they were safe to eat. So 20 00:01:11,520 --> 00:01:16,480 Speaker 1: how can koala's eat eucalyptus. Koalas have cheek teeth that 21 00:01:16,640 --> 00:01:19,399 Speaker 1: grind up the tough leaves, and their other teeth are 22 00:01:19,440 --> 00:01:22,800 Speaker 1: spaced specifically to slice the leaves into smaller pieces that 23 00:01:22,880 --> 00:01:26,880 Speaker 1: they can swallow. But the most important part happens inside 24 00:01:26,880 --> 00:01:30,600 Speaker 1: their bodies when their eucalyptus friendly digestive system takes over. 25 00:01:32,120 --> 00:01:35,280 Speaker 1: Just as we humans all have a microbiome inside our 26 00:01:35,319 --> 00:01:39,039 Speaker 1: guts to help us digest our food, Aquala's digestive tract 27 00:01:39,200 --> 00:01:42,640 Speaker 1: is full of different types of bacteria that make eucalyptus 28 00:01:42,720 --> 00:01:46,959 Speaker 1: both safe and somewhat digestible. A koala has an organ 29 00:01:47,080 --> 00:01:49,920 Speaker 1: called a secum. Humans actually have it too, but a 30 00:01:50,000 --> 00:01:54,200 Speaker 1: koala is much bigger. The secum contains bacteria that break 31 00:01:54,280 --> 00:01:57,520 Speaker 1: down the eucalyptus fibers. This makes it so that at 32 00:01:57,560 --> 00:02:01,360 Speaker 1: least some of the leaf about can be digested that 33 00:02:01,520 --> 00:02:05,480 Speaker 1: is converted into calories for nutrition and energy. There are 34 00:02:05,480 --> 00:02:09,160 Speaker 1: other digestive trick is bacterium that neutralizes the toxins in 35 00:02:09,200 --> 00:02:13,560 Speaker 1: eucalyptus oil mostly sine, all the poisonous component that makes 36 00:02:13,600 --> 00:02:18,119 Speaker 1: the leaves unsafe for most mammals. Of the roughly five 37 00:02:18,200 --> 00:02:21,680 Speaker 1: hundred types of eucalyptus trees out there, kualas only go 38 00:02:21,800 --> 00:02:25,400 Speaker 1: for a couple dozen types, and of those, any particular 39 00:02:25,440 --> 00:02:28,800 Speaker 1: group of koalas will have a few favorites. Eating the 40 00:02:28,840 --> 00:02:32,120 Speaker 1: same few types of eucalyptus all the time probably helps 41 00:02:32,160 --> 00:02:34,480 Speaker 1: kuala's learn the scent of a leaf that has a 42 00:02:34,520 --> 00:02:38,760 Speaker 1: different toxic substance in it, called prussic acid. Prussic acid 43 00:02:38,840 --> 00:02:41,200 Speaker 1: is toxic even to koala's, so they have to be 44 00:02:41,320 --> 00:02:45,959 Speaker 1: very careful not to eat those leaves. It's not hard 45 00:02:46,000 --> 00:02:49,079 Speaker 1: to see why a koala might smell like eucalyptus, since 46 00:02:49,120 --> 00:02:51,600 Speaker 1: it's pretty much all they eat, and this means that 47 00:02:51,680 --> 00:02:54,519 Speaker 1: koalas hardly ever have to leave the trees, so they're 48 00:02:54,520 --> 00:02:56,919 Speaker 1: out of reach from the countless predators who would find 49 00:02:56,960 --> 00:03:00,160 Speaker 1: the twenty five pound or about eleven kilo slow moveing 50 00:03:00,160 --> 00:03:03,960 Speaker 1: marsupial and easy target. It also means they can sometimes 51 00:03:04,120 --> 00:03:07,880 Speaker 1: smell like cough drops only sometimes, though it's mostly the 52 00:03:07,919 --> 00:03:11,800 Speaker 1: young koalas that give off a slight eucalyptus scent. Adult 53 00:03:11,840 --> 00:03:14,840 Speaker 1: kuala is apparently smell more like a mixture of urine 54 00:03:14,840 --> 00:03:19,160 Speaker 1: and kuala mating musk, according to the Australian Kuala Foundation. 55 00:03:21,160 --> 00:03:25,200 Speaker 1: But here we come to an interesting question. If eucalyptus 56 00:03:25,200 --> 00:03:28,080 Speaker 1: oil is toxic, how can it be used in cough drops. 57 00:03:28,800 --> 00:03:32,760 Speaker 1: As with most substances, it's all about moderation. What's toxic 58 00:03:32,760 --> 00:03:36,360 Speaker 1: at high doses can be neutral or beneficial in small amounts. 59 00:03:36,600 --> 00:03:39,960 Speaker 1: Kualas eat lots of different types of eucalyptus leaves, some 60 00:03:40,080 --> 00:03:44,160 Speaker 1: of which contain tremendous amounts of toxins like seniol. Oil 61 00:03:44,160 --> 00:03:48,280 Speaker 1: from eucalyptus leaves can be up to seni al. Most 62 00:03:48,320 --> 00:03:52,000 Speaker 1: herbal remedies containing eucalyptus, which date back at least hundreds 63 00:03:52,040 --> 00:03:55,200 Speaker 1: of years in the aboriginal cultures of Australia, come from 64 00:03:55,240 --> 00:03:58,720 Speaker 1: the blue gum species. The oil in blue gum leaves 65 00:03:58,720 --> 00:04:02,760 Speaker 1: contains much less senniol, as little as four percent by volume. 66 00:04:04,320 --> 00:04:07,560 Speaker 1: Eucalyptus oil finds its way into cough drops mostly because 67 00:04:07,560 --> 00:04:11,520 Speaker 1: of its anti inflammatory properties, which are attributed to the seniol. 68 00:04:12,160 --> 00:04:17,440 Speaker 1: Eucalyptus also has both antimicrobial and antibacterial properties. It's used 69 00:04:17,440 --> 00:04:20,279 Speaker 1: in herbal medicine to treat everything from the common cold 70 00:04:20,360 --> 00:04:25,400 Speaker 1: to fungal infections to bronchitis. With all of eucalyptus oils 71 00:04:25,400 --> 00:04:29,280 Speaker 1: medicinal applications, you'd think koalas would be protected against just 72 00:04:29,320 --> 00:04:32,839 Speaker 1: about every nuisance out there, but no, they're still subject 73 00:04:32,880 --> 00:04:37,200 Speaker 1: to their own health concerns. Eucalyptus oils may protect eucalyptus 74 00:04:37,240 --> 00:04:40,720 Speaker 1: trees from bugs and parasites, but kualas have as many 75 00:04:40,800 --> 00:04:43,800 Speaker 1: ticks as the next marsupial and they also have the 76 00:04:43,839 --> 00:04:49,239 Speaker 1: sexually transmitted disease chlamydia in strangely large numbers. Aside from that, though, 77 00:04:49,520 --> 00:04:52,960 Speaker 1: the biggest threads to koalas are domestic dogs, speeding cars, 78 00:04:53,120 --> 00:04:57,719 Speaker 1: and of course, greenhouse gases and increasing carbon dioxide maybe 79 00:04:57,720 --> 00:05:00,839 Speaker 1: sapping what few nutrients Eucalyptus ly eaves have to offer, 80 00:05:02,040 --> 00:05:05,160 Speaker 1: and in the early nineteen hundreds, kouala fur was all 81 00:05:05,160 --> 00:05:09,200 Speaker 1: the rage. Eight million kualas were killed between nineteen nineteen 82 00:05:09,200 --> 00:05:13,040 Speaker 1: and nineteen twenty four alone. In the late nineteen twenties, 83 00:05:13,120 --> 00:05:17,520 Speaker 1: countries started protecting koalas, which are now considered a vulnerable species. 84 00:05:17,920 --> 00:05:20,760 Speaker 1: There are only about a hundred thousand left in the wild. 85 00:05:26,200 --> 00:05:29,039 Speaker 1: Today's episode is based on the article du Kouala smell 86 00:05:29,040 --> 00:05:31,560 Speaker 1: at Cough drops on house to works dot com, written 87 00:05:31,600 --> 00:05:34,599 Speaker 1: by Julia Layton. Brainstuff is production of by Heart Radio 88 00:05:34,760 --> 00:05:36,920 Speaker 1: in partnership with how stuff works dot Com and is 89 00:05:36,920 --> 00:05:40,320 Speaker 1: produced by Tyler Play four more podcasts from my heart Radio. 90 00:05:40,520 --> 00:05:43,279 Speaker 1: Visit the I heart Radio app, Apple Podcasts, or wherever 91 00:05:43,320 --> 00:05:44,760 Speaker 1: you listen to your favorite shows.