WEBVTT - Do Koalas Smell Like Cough Drops? 0:00:01.920 --> 0:00:04.320 Welcome to brain Stuff, a production of I Heart Radio, 0:00:06.200 --> 0:00:11.160 Hey brain Stuff, Lauren Vogelbaum. Here in the eucalyptus forests 0:00:11.200 --> 0:00:15.120 of Australia, you'll find the world's remaining wild koalas eating 0:00:15.200 --> 0:00:18.880 leaves and sleeping. That's pretty much all these marsupials do. 0:00:19.480 --> 0:00:22.080 They sleep for up to twenty hours a day, cradled 0:00:22.079 --> 0:00:25.120 in eucalyptus branches, wake up to eat some leaves, and 0:00:25.320 --> 0:00:28.400 go back to snoozing on a full stomach. It's a 0:00:28.480 --> 0:00:32.440 lazy life that revolves around a monotonous diet, and koalas 0:00:32.479 --> 0:00:37.000 are perfectly adapted to it. Eucalyptus leaves have very little 0:00:37.080 --> 0:00:40.760 nutritional value, provide almost no energy in the form of calories, 0:00:41.000 --> 0:00:44.440 are hard to digest, and are poisonous to almost every 0:00:44.440 --> 0:00:49.280 mammal besides the koala. Perhaps, needless to say, kuala's face 0:00:49.360 --> 0:00:53.000 little competition for their favorite food source. They consume up 0:00:53.000 --> 0:00:55.040 to one and a half pounds or six hundred and 0:00:55.040 --> 0:00:57.800 eighty grams of leaves in a single day. That's about 0:00:57.800 --> 0:01:00.880 a thousand leaves. They spend pretty much all of the 0:01:00.960 --> 0:01:04.200 energy they get from the leaves on chewing and digesting them. 0:01:04.720 --> 0:01:07.880 Eucalyptus leaves are so fibrous that most animals wouldn't go 0:01:07.920 --> 0:01:11.280 near them even if they were safe to eat. So 0:01:11.520 --> 0:01:16.480 how can koala's eat eucalyptus. Koalas have cheek teeth that 0:01:16.640 --> 0:01:19.399 grind up the tough leaves, and their other teeth are 0:01:19.440 --> 0:01:22.800 spaced specifically to slice the leaves into smaller pieces that 0:01:22.880 --> 0:01:26.880 they can swallow. But the most important part happens inside 0:01:26.880 --> 0:01:30.600 their bodies when their eucalyptus friendly digestive system takes over. 0:01:32.120 --> 0:01:35.280 Just as we humans all have a microbiome inside our 0:01:35.319 --> 0:01:39.039 guts to help us digest our food, Aquala's digestive tract 0:01:39.200 --> 0:01:42.640 is full of different types of bacteria that make eucalyptus 0:01:42.720 --> 0:01:46.959 both safe and somewhat digestible. A koala has an organ 0:01:47.080 --> 0:01:49.920 called a secum. Humans actually have it too, but a 0:01:50.000 --> 0:01:54.200 koala is much bigger. The secum contains bacteria that break 0:01:54.280 --> 0:01:57.520 down the eucalyptus fibers. This makes it so that at 0:01:57.560 --> 0:02:01.360 least some of the leaf about can be digested that 0:02:01.520 --> 0:02:05.480 is converted into calories for nutrition and energy. There are 0:02:05.480 --> 0:02:09.160 other digestive trick is bacterium that neutralizes the toxins in 0:02:09.200 --> 0:02:13.560 eucalyptus oil mostly sine, all the poisonous component that makes 0:02:13.600 --> 0:02:18.119 the leaves unsafe for most mammals. Of the roughly five 0:02:18.200 --> 0:02:21.680 hundred types of eucalyptus trees out there, kualas only go 0:02:21.800 --> 0:02:25.400 for a couple dozen types, and of those, any particular 0:02:25.440 --> 0:02:28.800 group of koalas will have a few favorites. Eating the 0:02:28.840 --> 0:02:32.120 same few types of eucalyptus all the time probably helps 0:02:32.160 --> 0:02:34.480 kuala's learn the scent of a leaf that has a 0:02:34.520 --> 0:02:38.760 different toxic substance in it, called prussic acid. Prussic acid 0:02:38.840 --> 0:02:41.200 is toxic even to koala's, so they have to be 0:02:41.320 --> 0:02:45.959 very careful not to eat those leaves. It's not hard 0:02:46.000 --> 0:02:49.079 to see why a koala might smell like eucalyptus, since 0:02:49.120 --> 0:02:51.600 it's pretty much all they eat, and this means that 0:02:51.680 --> 0:02:54.519 koalas hardly ever have to leave the trees, so they're 0:02:54.520 --> 0:02:56.919 out of reach from the countless predators who would find 0:02:56.960 --> 0:03:00.160 the twenty five pound or about eleven kilo slow moveing 0:03:00.160 --> 0:03:03.960 marsupial and easy target. It also means they can sometimes 0:03:04.120 --> 0:03:07.880 smell like cough drops only sometimes, though it's mostly the 0:03:07.919 --> 0:03:11.800 young koalas that give off a slight eucalyptus scent. Adult 0:03:11.840 --> 0:03:14.840 kuala is apparently smell more like a mixture of urine 0:03:14.840 --> 0:03:19.160 and kuala mating musk, according to the Australian Kuala Foundation. 0:03:21.160 --> 0:03:25.200 But here we come to an interesting question. If eucalyptus 0:03:25.200 --> 0:03:28.080 oil is toxic, how can it be used in cough drops. 0:03:28.800 --> 0:03:32.760 As with most substances, it's all about moderation. What's toxic 0:03:32.760 --> 0:03:36.360 at high doses can be neutral or beneficial in small amounts. 0:03:36.600 --> 0:03:39.960 Kualas eat lots of different types of eucalyptus leaves, some 0:03:40.080 --> 0:03:44.160 of which contain tremendous amounts of toxins like seniol. Oil 0:03:44.160 --> 0:03:48.280 from eucalyptus leaves can be up to seni al. Most 0:03:48.320 --> 0:03:52.000 herbal remedies containing eucalyptus, which date back at least hundreds 0:03:52.040 --> 0:03:55.200 of years in the aboriginal cultures of Australia, come from 0:03:55.240 --> 0:03:58.720 the blue gum species. The oil in blue gum leaves 0:03:58.720 --> 0:04:02.760 contains much less senniol, as little as four percent by volume. 0:04:04.320 --> 0:04:07.560 Eucalyptus oil finds its way into cough drops mostly because 0:04:07.560 --> 0:04:11.520 of its anti inflammatory properties, which are attributed to the seniol. 0:04:12.160 --> 0:04:17.440 Eucalyptus also has both antimicrobial and antibacterial properties. It's used 0:04:17.440 --> 0:04:20.279 in herbal medicine to treat everything from the common cold 0:04:20.360 --> 0:04:25.400 to fungal infections to bronchitis. With all of eucalyptus oils 0:04:25.400 --> 0:04:29.280 medicinal applications, you'd think koalas would be protected against just 0:04:29.320 --> 0:04:32.839 about every nuisance out there, but no, they're still subject 0:04:32.880 --> 0:04:37.200 to their own health concerns. Eucalyptus oils may protect eucalyptus 0:04:37.240 --> 0:04:40.720 trees from bugs and parasites, but kualas have as many 0:04:40.800 --> 0:04:43.800 ticks as the next marsupial and they also have the 0:04:43.839 --> 0:04:49.239 sexually transmitted disease chlamydia in strangely large numbers. Aside from that, though, 0:04:49.520 --> 0:04:52.960 the biggest threads to koalas are domestic dogs, speeding cars, 0:04:53.120 --> 0:04:57.719 and of course, greenhouse gases and increasing carbon dioxide maybe 0:04:57.720 --> 0:05:00.839 sapping what few nutrients Eucalyptus ly eaves have to offer, 0:05:02.040 --> 0:05:05.160 and in the early nineteen hundreds, kouala fur was all 0:05:05.160 --> 0:05:09.200 the rage. Eight million kualas were killed between nineteen nineteen 0:05:09.200 --> 0:05:13.040 and nineteen twenty four alone. In the late nineteen twenties, 0:05:13.120 --> 0:05:17.520 countries started protecting koalas, which are now considered a vulnerable species. 0:05:17.920 --> 0:05:20.760 There are only about a hundred thousand left in the wild. 0:05:26.200 --> 0:05:29.039 Today's episode is based on the article du Kouala smell 0:05:29.040 --> 0:05:31.560 at Cough drops on house to works dot com, written 0:05:31.600 --> 0:05:34.599 by Julia Layton. Brainstuff is production of by Heart Radio 0:05:34.760 --> 0:05:36.920 in partnership with how stuff works dot Com and is 0:05:36.920 --> 0:05:40.320 produced by Tyler Play four more podcasts from my heart Radio. 0:05:40.520 --> 0:05:43.279 Visit the I heart Radio app, Apple Podcasts, or wherever 0:05:43.320 --> 0:05:44.760 you listen to your favorite shows.