It's not hard to see why a koala might smell like eucalyptus. It's pretty much all they eat. This means koalas hardly ever have to leave the trees, so they're out of reach from the countless predators who would find the little 25-pound (about 11 kg), slow-moving marsupial an 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 koalas smell more like a mixture of urine and koala-mating musk, according to the Australian Koala Foundation.
And 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 beneficial in small amounts. Koalas eat lots of different types of eucalyptus leaves, some of which contain tremendous amounts of toxins like cineole. Oil from eucalyptus leaves can be up to 95 percent cineole. Most herbal remedies containing eucalyptus, which date back at least hundreds of years in the Aboriginal tribes of Australia, come from the species E. globulusis, or blue gum. The oil in blue gum leaves contains much less cineole, as little as 4 percent by volume [source: Cornell].
Eucalyptus oil finds its way into cough drops mostly because of its anti-inflammatory properties, which are attributed to the cineole. But it doesn't stop there: Eucalyptus is something of an "alternative medicine" cure-all. It's an antiseptic and a sedative, and it has both antimicrobial (kills viruses) and antibacterial properties. It's used in herbal medicine to treat everything from the common cold to fungal infections to bronchitis. It may even help with ear infections [source: UMMC].
With all of eucalyptus oil's 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 koalas have as many ticks as the next marsupial. They also have the sexually transmitted disease chlamydia in strangely large numbers [source: Science Daily]. Aside from that, though, the biggest threats to koalas are domestic dogs, speeding cars and, of course, greenhouse gasses: An increase in carbon dioxide may be sapping what few nutrients eucalyptus leaves have to offer.
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