Koalas and Hot Weather: How to Help on a Hot Adelaide Day
Adelaide summers are hard on koalas. When temperatures climb above 37 degrees, koalas begin to experience genuine heat stress and when the mercury approaches 40 degrees or beyond, the situation can become life-threatening.
Koalas are less resilient to prolonged heat than most other marsupials, and the combination of hot weather and dry conditions reduces the moisture content in eucalyptus leaves, meaning their primary water source fails them at exactly the wrong time. Knowing what you are seeing and what to do can make the difference for a koala struggling through an Adelaide summer.
Koalas are less resilient to prolonged heat than most other marsupials, and the combination of hot weather and dry conditions reduces the moisture content in eucalyptus leaves, meaning their primary water source fails them at exactly the wrong time. Knowing what you are seeing and what to do can make the difference for a koala struggling through an Adelaide summer.
What does it mean if a koala is on the ground?
Koalas spend almost their entire lives in trees. When a koala comes to the ground on a hot day, it is telling you something important. It needs water and it is struggling.
In hot dry conditions the moisture content in eucalyptus leaves drops significantly.
Koalas rely on their food for most of their daily water intake, so when the leaves dry out, they can become severely dehydrated quickly.
Research from the University of Sydney has confirmed that koalas actively seek free water during heat events, coming to the ground to drink from bowls, puddles and any available source they can find. You can read more about what science says about koalas and water here.
- If you see a koala on the ground on a hot day, place a bowl of water nearby and step well back. Never offer water in a bottle. Water from an upturned bottle can enter the koala's airways and cause further harm. A bowl on the ground is always the right approach.
- Keep dogs and children away and give the koala space to drink without being disturbed. A koala that drinks and then climbs back up a tree is doing exactly what it should. One that stays on the ground for an extended period, or that appears to be drinking excessively, needs more than water. It needs a rescue call.
Excessive drinking in a koala can be a sign of disease or another serious health issue, not just thirst. Read more about oxalate nephrosis and why prolonged drinking is a major clinical concern.
Not sure if the koala is thirsty or needs more help? Read What to Do if you Find a Koala on the Ground - this will give you important advice.
Why do koalas hug tree trunks in the heat?
If you see a koala pressed low against a tree trunk with all four limbs wrapped tightly around it, this is not distress. It is a sophisticated cooling strategy.
Research published in Biology Letters (Briscoe et al., 2014) found that tree trunks can be up to 9 degrees cooler than the surrounding air temperature on a hot day. By hugging the trunk, koalas conduct heat directly out of their bodies into the cooler wood, reducing how much water they need to lose through panting and evaporative cooling by up to half.
Large established trees are not just habitat for koalas. On a 40 degree Adelaide day they are survival infrastructure. A koala hugging a trunk low to the ground is managing its temperature and generally does not need intervention.
A bowl of water at the base of the tree is always welcome.
You can lightly mist the trunk above the koala so water trickles down slowly, but do not mist the koala directly unless instructed by a wildlife rescuer.
If you see a koala pressed low against a tree trunk with all four limbs wrapped tightly around it, this is not distress. It is a sophisticated cooling strategy.
Research published in Biology Letters (Briscoe et al., 2014) found that tree trunks can be up to 9 degrees cooler than the surrounding air temperature on a hot day. By hugging the trunk, koalas conduct heat directly out of their bodies into the cooler wood, reducing how much water they need to lose through panting and evaporative cooling by up to half.
Large established trees are not just habitat for koalas. On a 40 degree Adelaide day they are survival infrastructure. A koala hugging a trunk low to the ground is managing its temperature and generally does not need intervention.
A bowl of water at the base of the tree is always welcome.
You can lightly mist the trunk above the koala so water trickles down slowly, but do not mist the koala directly unless instructed by a wildlife rescuer.
How to help koalas on a hot day
The most effective thing any Adelaide resident can do during a heatwave is put out bowls of fresh water. Keep them topped up, keep them clean, and place them somewhere shaded where animals can reach them without being exposed to more heat in the process.
Always use a bowl, never an upturned bottle. Water from a bottle can enter a koala's airways.
If you have a swimming pool and there are koalas in your area, secure a flotation device to a rope attached to something solid outside the pool. A pool noodle, a plank of wood or a large plastic container will do. Koalas can fall into pools and will drown if they cannot find something to grip and climb out on.
Keep dogs secured on extreme heat days. Dogs do not need to attack a koala to cause serious harm. A chase alone is enough to fatally overheat an animal that is already heat stressed.
The most important thing after putting out water is to stay back. A stressed koala produces high levels of cortisol, which raises its heart rate and makes recovery harder. Even well meaning human presence adds stress. Give them space and let them drink in peace.
When to call for help — the signs a koala needs a vet
Not every koala on the ground needs rescuing. But some do, and knowing the difference matters.
Call a wildlife rescue organisation if the koala has not climbed back up a tree after a reasonable period and the temperature is still high.
Call if the koala appears to be drinking excessively or has been on the ground for an unusually long time. Excessive water consumption is a significant clinical warning sign and can indicate serious kidney disease rather than straightforward dehydration.
Call if the koala appears disoriented, lethargic or unresponsive. And call immediately if the koala approaches you or allows you to get close without moving away. A koala that has lost its natural wariness of people is in serious distress. Their fear of humans is protective and when it disappears, the animal is in crisis.
Do not attempt to handle, capture or move the koala yourself. Koalas have strong arms, sharp claws and a powerful grip, and handling adds significant additional stress to an already compromised animal. Note the exact location and call your local wildlife rescue group.
Our clinic provides free veterinary treatment for koalas brought in by rescue groups across South Australia. We rely on the rescue network to get animals to us safely.
If you do have concerns about any koala at any time or any season, please call a koala rescue organisation (or wildlife rescue group) in your area. The list of South Australian koala rescue groups can be found on our contact us page
Heatwaves bring a surge of koalas needing urgent care
During Adelaide's hottest days our clinic sees a dramatic increase in heat-stressed and dehydrated koalas. Every one of them receives free veterinary treatment — funded entirely by donations from people like you.
Help a Heat-Stressed Koala TodayTax deductible · DGR registered charity · ABN 74 834 255 299
References:
Briscoe et al. (2014) Tree-hugging koalas demonstrate a novel thermoregulatory mechanism for arboreal mammals. Biology Letters. Mella et al. (2024) Hot climate, hot koalas: the role of weather, behaviour and disease on thermoregulation. Conservation Physiology.
Briscoe et al. (2014) Tree-hugging koalas demonstrate a novel thermoregulatory mechanism for arboreal mammals. Biology Letters. Mella et al. (2024) Hot climate, hot koalas: the role of weather, behaviour and disease on thermoregulation. Conservation Physiology.