Koalas Hug Trees to Regulate Heat, Study Finds

Koalas hug trees in order to cope with extreme heat, a new study reveals.

The tree-dwelling herbivorous marsupial is one of Australia's best known animals. Sadly, these koalas are in trouble as their numbers are declining alarmingly. The drastic change in the climate is a major factor contributing to their decline as heat waves and rising temperatures hit the koala population hard.

"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 latest study by researchers at the University of Melbourne can help in conservation of the koalas that are listed as threatened species by the Australian government. The study also helps understand the impact of climate change on animals.

In this study the researchers found that koalas cope with extreme heat by resting against the cooler tree trunks. This finding was based on the analysis of thermal images.

The researchers looked at the behavior of 30 koalas in hot conditions at French Island, towards the east of the city.  The behavior of the marsupials, who sleep 18-20 hours a day, was monitored using radio collars.

Koalas are wrapped in thick fur and this not just helps them keep warm but also prevents loss of body heat. The researchers had earlier assumed that the koalas expose their front that is layered with less insulating thinner fur to the air to lose heat. But surprisingly in this study the researchers found the reverse of it, reports abc news.

They noticed that the Koalas wrap their bodies around the cooler lower regions of the trunks, where the temperature is estimated to be below 9°C below air temperature.

Koalas lick their fur and pant due to the heat, which further lowers their body temperature, and also increases the risk of dehydration. But the researchers found that tree hugging behavior helps the koalas release the heat without getting dehydrated. 

"We found trunks of some tree species can be over 5°C cooler than the air during hot weather," lead researcher Natalie Briscoe, from the University's School of Botany, said. "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."

Measuring the temperatures of the Koalas and the trees using portable equipment, the researchers  realized that tree hugging was a cooling behavior during extreme heat. The marsupials transferred the heat to the tree.

Accessibility to cooler trees should be a factor while assessing habitat for the Koalas under current and future climate scenarios.

The finding was documented in Biology Letters.