Koalas Hug Trees to Keep Cool

University of Melbourne researchers have found that Koalas try to cool their bodies by hugging trees.

Recent heat waves in Australia have led to a decline in koala population. "About a quarter of the koalas in one population died during a heat-wave of 2009, so understanding the types of factors that can make some populations more resilient is important," said Professor Andrew Krockenberger from James Cook University, one of the study authors.

The study explains why some types of the furry animals are better equipped to deal with the heat than others.

Koalas sleep for about 18 to 20 hours a day. They have a thick coat of fur that traps heat. Researchers had assumed that the animal would want to expose the front part of its body to the air during summer as it has a thinner insulating fur layer there. To their surprise, they found that koalas hugged tree trunks during summer to transfer heat from their body to the tree, abc news reported.  

"They'd just flop over the [lower] tree trunks," Dr Michael Kearney from the University of Melbourne told BBC. "It looked like they were spread-eagled and uncomfortable; it seemed like the wrong thing to do."

Researchers used cameras and portable weather station to closely monitor koalas' behavior during summer.

The team found that the animals transferred body temperature by staying close to the tree trunks.

Thermal images showed that the animals were "dumping heat into the tree," BBC reported.

Hugging trees is a more efficient way of staying cool because it doesn't lead to loss of water. Other methods of reducing body temperature such as licking and panting result in dehydration, researchers said.

"We found trunks of some tree species can be over 5°C cooler than the air during hot weather," she said, "Natalie Briscoe, from the University's School of Botany, "Access to these trees can save about half the water a koala would need to keep cool on a hot day. This significantly reduces the amount of heat stress for koalas."

Previous research has shown that the furry little animals are already stressed-out due to human activities. University of Melbourne researchers had recently shown that noise and popular tourist attractions such as "koala encounters," are damaging the animals' health.

The present study results will help scientists understand how koalas will cope with global warming. Researchers found that the coolest tree for koalas was acacia, abc news reported.

"The availability of cooler trees should be considered when assessing habitat suitability under current and future climate scenarios," Dr Michael Kearney said in a news release.

The study is published in the journal Royal Society journal Biology Letters.