For most of the day and night, koalas barely move. They nap curled into tree forks, or chew carefree on eucalyptus leaves. But for a few fleeting minutes, usually just 10 out of 1,440, they come down to the ground. And that’s when they’re most likely to die.
New research reveals that these brief terrestrial forays account for two-thirds of all recorded koala deaths, mostly from dog attacks and car strikes. The findings offer an unusually detailed look into a long-overlooked sliver of the koala’s daily life, but also insights into how conservationists might keep the beloved marsupial from slipping further toward extinction.
“Koalas are mostly tree-dwelling, but due to extensive land clearing, they’re increasingly forced to travel on the ground, which puts them at serious risk of injury and death,” said Gabriella Sparkes, a Ph.D. student at the University of Queensland.
A Dangerous Descent
Koalas, often perceived as slow-moving tree-huggers, are not built for the ground. Their curved claws are perfect for climbing, not walking. And yet, as their forest homes are carved into paddocks and suburbs, the ground becomes unavoidable.
Sparkes wanted to understand what really happens when a koala leaves the canopy. How far do they travel? How quickly do they move? And how often do they descend?
“These are critical knowledge gaps if we want to identify high-risk areas or times and develop strategies to reduce threats during these vulnerable moments,” she said
To answer these questions, her team fitted wild koalas with GPS collars and motion sensors. Every five minutes, the GPS would log a location. When a koala was on the ground, that rate jumped to a location every five seconds, so the marsupial’s movements could be more finely tracked during this very short but vulnerable time.
Alongside GPS, the team used six-axis accelerometers that can detect subtle changes in motion and orientation. This allowed them to differentiate between walking, climbing, and sitting. When paired with GPS, the result was an unusually fine-grained portrait of koala behavior.
“This gives us an incredibly detailed view of how koalas move through their habitat,” said Sparkes.
Less Than One Percent of Their Day on the Ground
The data revealed something both expected and startling.
Yes, koalas spend most of their lives in trees. But they use the ground far less than anyone anticipated.
“What surprised us was how infrequently and briefly they use the ground—just 2–3 times per night, averaging around 10 minutes in total, or less than 1% of their day,” said Sparkes.
And when they are down, they don’t move quickly. Most of the time, they pause, sit, and slowly assess their surroundings. Only a tiny fraction (around 7%) of their time on the ground is spent bounding, a rapid movement that resembles a gallop.
“They spent nearly as much time sitting and pausing as they did walking,” said Sparkes. “This may indicate that koalas are carefully assessing their environment as they move, possibly evaluating trees before selecting one to climb, or it may reflect the energetic costs of bounding.”
Those pauses, though, may make them vulnerable. The longer they spend hesitating between trees, the more likely they are to encounter a dog or cross a road with traffic.
Designing Safer Landscapes
This study, presented at the Society for Experimental Biology Annual Conference on July 9, is the first to closely document the ground-based behavior of wild koalas in such detail. But it opens broader questions.
If researchers can pinpoint what makes koalas stay in trees longer, whether it’s the species of tree, the shape of the canopy, or the structure of the landscape, they might be able to design habitats that reduce dangerous ground crossings.
“We’re now looking at environmental features that influence how long koalas stay in trees,” said Sparkes. “If we can identify the kinds of trees or habitat conditions that encourage koalas to remain in trees for longer, we may be able to design or manage landscapes in ways that reduce the need for ground travel.”
That could mean planting specific types of trees, bridging gaps in the canopy, or protecting corridors that allow koalas to move from tree to tree without touching the ground. These interventions could save many koalas, especially since the iconic species has already been declared endangered in many parts of Australia.
“This research is just one piece of the puzzle, but it adds an important layer to our understanding of how koalas interact with increasingly human-altered environments,” said Sparkes.
