Why Koalas Smell Like Cough Drops When They’re Young

You are what you eat. Chowing down on a giant bowl of garlic cloves will make you smell like garlic. The same goes for onions. For younger koalas, however, their odor is usually a little more pleasant. Thanks to a diet consisting almost entirely of eucalyptus leaves, koalas emit the unmistakable smell of cough drops. Koalas are one of the most recognizable animals in the world and an enduring symbol of Australian wildlife. They spend most of their lives in groves of eucalyptus trees, munching on leaves when they aren’t sleeping. This singular diet gives some of them a unique scent. How does this happen? Let’s learn more about koalas and how their toxic diet affects their smell.

Koala Basics

Koalas (Phascolarctos cinereus) are the only extant member of the family Phascolarctidae. They may look like teddy bears, but wombats are their closest living relatives. Koalas are characterized by short, stout bodies, large heads, and fluffy ears. As marsupials, koalas give birth to underdeveloped joeys, who crawl into their mothers’ pouches and grow for another six months. Despite having almost no natural predators, koala numbers have steadily dwindled over the last few decades due to habitat destruction, disease (such as chlamydia), climate change, and other threats.

It’s hard to deny that koalas are strange little creatures. They make unique sounds and can catch sexually transmitted diseases. What’s more, baby koalas or joeys eat their mother’s poop. Koalas are nocturnal, solitary, and slow-moving animals. They also sleep nearly twenty hours a day and feed almost entirely on poisonous eucalyptus leaves. This likely contributes to their name, which means “no drink” in the Australian Aboriginal language Dharug. Their diet also gives them a unique cough drop smell.

Eucalyptus Tree

Eucalyptus leaves may not have much nutritional value, but koalas make do with them. What’s more, they are poisonous to most animals. To get enough calories and nutrition, koalas typically eat between 200 to 500 grams (about 0.44 to 1.1 pounds) of eucalyptus leaves per day. Very few animals, such as some possums and gliders, can eat eucalyptus leaves, but koalas are the only large mammal to subsist almost exclusively on them. It’s taxing, however. Koalas use all of their energy in the few hours they are awake per day to find, eat, and digest eucalyptus leaves.

Koalas can manage this unsavory meal thanks to special features of their physiology. They have teeth in their cheeks to mash up tough leaves, and their other teeth are spaced in such a way that they can perfectly slice them into smaller, easy-to-swallow bits. Once the tough eucalyptus leaves have been sufficiently chewed, they move into the koala’s digestive tract.

Like other mammals, koalas have a caecum, a pouch at the beginning of the large intestine. However, koalas have much larger ceca than other mammals, and these contain bacteria that help break down the tough eucalyptus fibers. Koalas are able to digest and convert about 25% of an eucalyptus leaf into energy. Koalas’ stomachs contain bacteria that help neutralize the toxic components of eucalyptus oil. Additionally, koalas select specific types of eucalyptus trees (a few dozen out of the 500 species) that have lower levels of cineole. Cineole is poisonous, yet under the right conditions, medically beneficial.

Koala Cough Drops

Unsurprisingly, all that eucalyptus oil makes for a cough drop-scented koala. These marsupials spend their lives in eucalyptus and eat it for every meal, so it’s bound to secrete through their pores. That said, not all koalas smell like cough drops. It’s usually the younger ones that emit a characteristic eucalyptus smell, a kind of earthy mint or menthol. Mature koalas typically have a more unpleasant odor; they smell like a mixture of urine and musk.

The difference between medicine and poison is the dose, and eucalyptus oil embodies this adage. In high enough doses it can be fatal. When moderated, however, eucalyptus oil has incredible anti-inflammatory, antibacterial, and antimicrobial properties. Eucalyptus oil is often used in herbal remedies to treat a variety of ailments, from ear infections to the common cold.

While some eucalyptus varieties have leaves with oil comprised of nearly 95% cineole (the poisonous compound), others are safer. If you see eucalyptus oil in a medicinal ingredient list, it’s likely taken from E. globulus, or blue gum eucalyptus.

While a diet of eucalyptus leaves protects koalas from some bugs and parasites, it also exposes them to other risks. Besides suffering from an inordinate number of chlamydia infections, the dwindling eucalyptus habitats in Australia threaten koala populations. To make matters worse, increases in atmospheric carbon dioxide are depleting eucalyptus leaves’ scarce nutrients. Koalas are strange but fascinating creatures, and serious changes to environmental policies are needed to prevent further decline of koala populations and to ensure their long-term survival.