--- title: "Koala (Phascolarctos cinereus) | AnimalTracks.wiki" description: "A slow-motion marsupial that sleeps up to 22 hours a day and leans on gut bacteria to live on eucalyptus leaves most herbivores can't tolerate." image: "https://animaltracks.wiki/images/animals/koala-1.webp" published: "2026-09-01" updated: "2026-09-13" --- # Koala (*Phascolarctos cinereus*) > **Status**: Checked against 6 sources, listed under Sources below. > **Tagline**: A slow-motion marsupial that sleeps up to 22 hours a day and leans on gut bacteria to live on eucalyptus leaves most herbivores can't tolerate. > **Soundtrack Vibe**: Psychedelic Rock & Neo-Psych // Ocean Alley, "Confidence" > **Soundtrack Links**: [Spotify](https://open.spotify.com/track/3PwiD0JaTDiBMWDUW2hXNX) | [YouTube](https://www.youtube.com/watch?v=PGGjXdlbW58) > **Vibe Match**: Sun-drenched reverbed guitars over a deep, laid-back bassline, the register of a male koala's mating bellow: a novel vocal organ drops each inhalation to an average 27.1 Hz, 20 times lower than expected for an 8 kg animal. ## Biological Superpowers & Stats - **Taxonomy**: *Phascolarctos cinereus* - **Danger Level**: Low - **Conservation Status**: Vulnerable ([IUCN Red List](https://doi.org/10.2305/iucn.uk.2020-1.rlts.t16892a166496779.en)) - **Superpower**: A huge caecum, and gut bacteria that break down the eucalyptus toxins most herbivores can't tolerate. - **Habitat**: Eucalyptus forests below 600 meters, from northern Queensland to southwestern Victoria in eastern Australia - **Diet**: Almost exclusively eucalyptus leaves, preferring about three dozen of the more than 600 kinds of eucalypt; an adult can eat 500 grams a day - **Tags**: marsupial, woodland, herbivore ## Natural History & Behavior ## Running on Low Power The koala (*Phascolarctos cinereus*) has built its lifestyle around a bad diet. Eucalyptus leaves are tough and low in calories, so koalas save energy by moving only occasionally and sleeping 18 to 22 hours a day. Average weights run from 5.1 kilograms for northern females to 11.8 kilograms for southern males, with males running up to 50% heavier than females. In the south of their range, where koalas are generally larger, males average 78 centimeters in head-body length to females' 72. Koalas usually live 10 to 15 years. ## A Gut Built to Handle Poison Eucalyptus leaves carry chemical defenses, including tannins, phenolic compounds and terpenes, that most herbivores can't tolerate. Koalas manage on almost nothing else: an adult can eat 500 grams of leaves a day, and koalas prefer about three dozen of the more than 600 kinds of eucalypt. The trick is a supersized gut and the bacteria inside it. A koala's caecum is huge, and one of the bacteria living in the mucus around it is *Lonepinella koalarum*. > **A Tannin-Busting Bacterium** *Lonepinella koalarum* was > first isolated from the mucus around a koala's caecum, and it has been shown > to break down the tannin-protein complexes in eucalyptus leaves, complexes > that koalas cannot digest. ## Life Up a Tree Koalas live in eucalyptus forests below 600 meters in elevation, spread from northern Queensland to southwestern Victoria in eastern Australia. Two opposable thumbs on each hand and sharp claws give them their grip, and strong arm and shoulder muscles help them climb up to 46 meters to the top of a tree. Koalas cool off by licking their arms and stretching out while they rest. ## A Species Under Real Pressure Koalas were hunted hard for their fur: eight million were killed between 1919 and 1924 alone. Public outcry won them legal protection after 1927, but today they face other threats: dog attacks, cars that hit some of them, disappearing habitat, and chlamydia, a common infection whose primary culprit, *Chlamydia pecorum*, causes eye infections, reproductive disease and even death. The IUCN now lists the species as Vulnerable. ## Frequently Asked Questions ### How can koalas survive on a diet of toxic eucalyptus leaves? Every eucalyptus species contains chemical defenses against plant-eaters, including tannins, phenolic compounds and terpenes. Koalas carry gut bacteria that have been studied for breaking those defenses down. One of them, Lonepinella koalarum, first isolated from the mucus around a koala's caecum, has been shown to break down the tannin-protein complexes in eucalyptus leaves, complexes that koalas cannot digest. *(Source: [Dahlhausen et al. 2020]())* ### Why do koalas sleep up to 22 hours a day? Eucalyptus leaves don't give koalas many calories, so they save energy by moving only occasionally. Koalas sleep 18 to 22 hours a day. *(Source: [San Diego Zoo Wildlife Alliance]())* ### How small is a newborn koala? A newborn koala, called a joey, is about the size of a large jelly bean and weighs 0.4 to 1 gram. It's born blind and deaf, but it can still use its strong forelimbs and hands to crawl from the birth canal into its mother's pouch, where it attaches to a nipple and grows for the next six months. Once it's too big for the pouch, it rides on her back. *(Source: [San Diego Zoo Wildlife Alliance]())* ## Sources 1. [Phascolarctos cinereus (koala). Animal Diversity Web, University of Michigan.]() 2. [Koala. San Diego Zoo Wildlife Alliance.]() 3. [Woinarski & Burbidge (2020). Phascolarctos cinereus. The IUCN Red List of Threatened Species 2020: e.T16892A166496779.]() 4. [Charlton et al. (2013). Koalas use a novel vocal organ to produce unusually low-pitched mating calls. Current Biology.]() 5. [Dahlhausen et al. (2020). Isolation and sequence-based characterization of a koala symbiont: Lonepinella koalarum. PeerJ.]() 6. [Waugh et al. (2017). Infection with koala retrovirus subgroup B (KoRV-B), but not KoRV-A, is associated with chlamydial disease in free-ranging koalas (Phascolarctos cinereus). Scientific Reports.]() *Published September 1, 2026. 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