A new study on vulnerable koala populations has found the Australian icon could struggle to survive rising temperatures.

Research by a team at The University of Sydney has found the popular notion that koalas feed on and live in eucalyptus trees is a misconception.

The researchers say throughout the day koalas choose trees to forage for food and different trees with a more dense foliage to survive high daytime temperatures.

Dr Mathew Crowther, who led the study, says koalas need a combination of both the right kind of shelter trees and food trees to survive.

"Our research confirmed koalas shelter during the day in different types of trees to the eucalypts they feed on at night," he said.

"We found the hotter it is during the day the more koalas will tend to seek out bigger trees with denser foliage to try to escape those temperatures."

Dr Crowther says making sure a habitat has enough trees for koalas to feed from and protecting them from predators is not enough to ensure their survival.

The University of Sydney study tracked 40 koalas on farmland around Gunnedah in north-western New South Wales, over a three year period.

Dr Crowther says the results of the research call for a change in the management and conservation of koalas.

"One quarter of the koalas we studied perished in a heatwave in 2009 and Australia has just experienced the hottest year since climate records began," he said.

With temperatures increasing, without more help koalas could really start to feel the heat.

"The lack of understanding of the importance of shelter trees for koalas is particularly concerning given the increasing frequency of extreme weather events," Dr Crowther said.

"Exposure to prolonged high temperatures can result in heat stress, dehydration and eventually death."