Uncovering the Secrets of Koalas: Facts You’ve Likely Never Heard

A remarkable discovery has been made in the Australian region of Newcastle, published in the journal of Biological Conservation. Through a survey led by the University of Newcastle, thermal drone-mounted cameras were able to locate roughly 4,357 koalas throughout a territory spanning over 160,000 acres. Most notably, a thriving colony consisting of roughly 300 koalas was found in the fringe forests of Sugarloaf Conservation Area, a region previously unknown to the species. The technology was able to confirm the existence of joeys, indicating the population is successfully breeding. This “secret’ koala colony will aid in conservation research and is wonderful news for koalas as a whole.

Everyone’s favorite Australian marsupials are full of interesting surprises. Slightly resembling teddy bears, these tree-climbing mammals are typically found on the coast of Australia. From gender gaps in size to genetic quirks and current health threats, here are 10 facts that might change how you view these cuddly-looking marsupials.

This post was updated on July 13, 2025 to include the recent discovery of koala colonies near Newcastle.

1. Male Koalas are About 50% Bigger Than Females

Setting aside their fluffy ears and teddy bear looks for a second, you might be surprised to know male koalas are significantly larger than their female counterparts. Often, male koalas can weigh up to 50% more than females. Males on the larger end can reach about 30 pounds, while females are around 15 to 20 pounds.

This characteristic is often referred to as sexual dimorphism, or distinct, observable differences between the sexes of an organism. These differences help males compete for mates and establish dominance in their territories. Males also usually have a wider face compared to females, and they possess scent glands on their chest, which females lack. The scent gland on male koalas is used to communicate with other koalas. Using these scent glands, male koalas can mark their territory to establish dominance and attract mates. This is similar to how deer mark their territories during the breeding season, referred to as the deer rut.

2. Koalas are Crepuscular and Nocturnal

Koalas are considered to be crepuscular and nocturnal creatures. This means that they spend most of their daylight hours resting and are most energetic at night and twilight (dawn and dusk). Their diet of choice, eucalyptus, is pretty low in calories and filled with toxins, so it is useful for them to conserve energy by sleeping approximately 18-20 hours a day. Under the cover of darkness or low light is when they usually awake to climb, forage, and feed. Doing these necessary activities during twilight hours helps minimize heat stress and vulnerability.

3. Chlamydia is a Common Koala Infection

The sexually transmitted disease, chlamydia, can affect many species, but when koalas contract this infection, it can be devastating. The spread of this disease can be through direct contact with infected individuals. Direct contact not only includes mating; chlamydia can also be spread through bodily fluids or feces. Some infections are even spread from mother to her offspring through birth or feeding.

In koalas, this disease can cause blindness, infertility, urinary disease, and even death. Chlamydia is prevalent in some areas, with areas ranging from 0 to 89% affected in different populations. The probability of prevalence depends on the region and stress factors, including habitat fragmentation. Fortunately, recovery programs are exploring vaccines and targeted treatment to help combat this threat.

4. Koalas Split from Wombats 30-40 Million Years Ago

As much as they look like teddy bears, they are not bear cousins. These marsupials are more closely related to wombats. Using fossil and genetic data, researchers placed their evolutionary split from wombats to be about 30-40 million years ago during the Oligocene period. Both of these animals belong to the suborder Vombatiformes. Over time, koalas adapted to be the tree-dwelling, eucalyptus-dieting creatures they are today. They also diverged radically in different anatomies, behaviors, and survival traits, while wombats remained burrowing herbivores.

5. The Koala is the Last of its Kind

The koala is an extant species; this means it is the only living species in its genus, Phascolarctos, which was once richer in diversity. One extinct relative is Phascolarctos stirtoni, otherwise known as the giant koala. Dating back about 24 million years ago, this lineage evolved alongside the changing Australian ecosystems.

6. Their Main Resource is Under Threat

These marsupials almost exclusively eat eucalyptus trees. These trees provide not only nutrients but also water, allowing koalas to go days without drinking. Unfortunately, eucalyptus habitats critical to koalas are increasingly threatened by wildfires, agriculture, mining, urban expansion, and logging. Since European settlement, more than 80% of the koalas’ original habitat has been destroyed. Though koalas are found in a range of habitats, eucalyptus trees are critical for their survival.

The remaining habitats are mostly fragmented or broken into smaller segments. Fragmentation into these smaller segments makes them more likely to be hit by vehicles. Factors like habitat fragmentation and road construction have resulted in significant numbers of koala road deaths, with some regions reporting hundreds of fatalities along major highways each year. This further impacts the koalas by making it more difficult for them to move between habitats, find mates, food, and shelter.

7. Koalas Could be Extinct in New South Wales by 2050

The warning is clear. New South Wales reported that koalas could be gone from the wild by 2050 without immediate government intervention. In 2022, eastern Australian subspecies were listed as endangered. The main threats to koalas include fires, habitat loss, disease, and climate change.

Different programs, such as the World Wildlife Fund (WWF) have implored urgent protection, with scientists warning that protecting their habitats (eucalyptus trees) is just as critical as tackling disease.

8. Koalas Have Fingerprints that Resemble Humans’

It may surprise you to know these wombat relatives have actual fingerprints. These patterns are believed to help koalas grip bark and leaves while feeding and are thought to have evolved independently through convergent evolution with primates. To put it simply, there were similar pressures that koalas and primates faced to have evolved the fingerprint trait.

9. They Get it from Their Mama (gut microbes, that is)

Koalas do not develop their gut enzymes on their own; they require the right gut microbiome. They acquire this from their mother’s pap, a nutrient-rich fecal matter fed to joeys, which provides them with microbes essential for detoxifying eucalyptus. Studies show that these microbiomes are unique to each group of koalas and are maternally transmitted.

10. They Have Superior Taste Buds

Probably one of the most interesting facts about koalas is their taste buds. Out of the 600 eucalyptus species, koalas only choose to munch on about 20. They are able to detect edible leaves thanks to their extra bitter taste receptors (TAS2R). Having more of these taste receptors helps them to detect bitter tastes better than many other marsupials. This genetic edge, if you will, enables them to choose eucalyptus with lower toxins, making their taste buds a delicious key to their survival.

Why Do These Facts Matter?

From genetic adaptations to historical context, we are revealing how koalas continue to survive in an increasingly hostile world. This unique evolutionary marvel of a species also has an ecological vulnerability due to its threatened habitats and disease. Fingerprints, maternal microbiological wisdom, and specialized taste buds reflect their silent resilience, centuries in the making.

At the same time, these threats are not just biological footnotes; they are existential threats that require attention. We cannot just enjoy them as their teddy bear look-alikes; we have to act.

How Can We Help?

• Support habitat protection legislation that is centered around eucalyptus forests
• If you can, donate to koala hospitals and vaccination programs
• Plant native trees in areas with koalas or contribute to seedling projects.
• Advocate for climate action, cooler nights help koalas conserve their energy.

Final Thoughts

Koalas are much more than a cuddly symbol of Australia. These living examples of adaptation require our attention as their future is uncertain. The next time you encounter a koala, whether it is the sticker on your laptop, or in a zoo or other wildlife area, take a moment to appreciate the fingerprints that link us. Then ask yourself: How can we ensure they have a protected place in this world?