The koala population is facing a "massive decline" as hotter and more extreme weather increases due to climate change.
Researchers from the University of Sydney have said the effect of hotter weather could have a "disastrous" effect on koala populations as they are unable to seek shelter from the scorching temperatures.
Published in the online journal Ecography, the team said koalas are a good subject to study the effect of shifting weather patterns as they have a specialised diet of eucalyptus leaves: "[They] need to balance nutrient and water intake against toxins in the leaves, all of which can change with soil type and climate."
Over three years, the authors looked at tree selection between day and night in relation to daily maximum temperatures - koalas sleep during the day, so choose trees that are good for shelter and thermoregulation.
They found koalas selected taller trees with more shelter during the day and that as temperatures increased, koalas picked taller trees at lower elevations: "Our results demonstrate that koalas need taller trees, and non-feed species with shadier/denser foliage, to provide shelter from heat."
They said the findings show the need to plant more trees to offer protection from extreme weather in the future: "Retaining and planting trees that provide optimum habitat will help arboreal folivores cope with the more frequent droughts and heatwaves expected with climate change."
Lead researcher Mathew Crowther told Australia's Associated Press that climate change is a major problem facing koalas.
"Koalas are actually down at the bottom of trees dying," he said. "We could see massive declines ... it would be disastrous."
Crowther said he could not predict a time frame for how quickly populations will fall, but said more must be done to protect koalas.
"The implication is that longstanding land management practices of retaining and planting feed trees for koalas needs to be expanded to include shelter trees within the home range of each koala," he said.