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Study Says Australia’s Koalas Hug Tree Can Keep Cool

 According to the latest study hosted by Dr Michael Kearney from the University of Melbourne’s Department of Zoology, Koalas (Phascolarctos cinereus) choose to take rest against cooler tree trunks to manage heat wave events, which can greatly affect koala populations In Australia.


Thermal image of a koala hugging the cool lower limb of a tree, illustrating a posture typically observed during hot weather. Image credit: Natalie J. Briscoe et al.

As Prof Andrew Krockenberger from James Cook University, the co-author of the paper published in the newest edition of the journal Biology Letters said, it was commonly known that nearly a quarter of the koalas in one population in New South Wales died during a heat wave in 2009. Therefore, it is vital to better understand the types of factors helping allow some populations to become more resilient.

Dr Kearney and Prof Krockenberger together with their team were engaged in close observation of the behavior of 30 koalas during hot weather at French Island, Victoria.

With help of a portable weather station installed on a long pole, they were able to measure what experiences the koalas had in the places where they were intended to stay in comparison of the places available to them.

From their observation, it was found that koalas preferred to hug certain trunks of special tree species, which could be over 5 degrees Celsius cooler than the air during hot weather. If the koalas chose to sit on such trees, it would save about half the water necessary to keep them cool, thus greatly decreasing the amount of heat stress koalas had to face.

In their study, the researchers also found that the coolest trees were acacias, which were not regarded as the food tree for koalas. However, such cool trees were obviously fundamental for koalas to fight against the heat.

Apart from koalas, cool tree trunks are also considered as important microhabitat under the hot wave for other tree dwelling species such as birds, leopards, primates as well as invertebrates.

It was strongly suggested by the scientists that the availability of cooler trees should be taken into account when habitat suitability were assessed under current and future climate situations.

From the team’s finding, koalas also liked to pant and lick their fur to keep cool, but it could cause dehydration as well.

 Journal reference: Natalie J. Briscoe et al. 2014. Tree-hugging koalas demonstrate a novel thermoregulatory mechanism for arboreal mammals. Biol. Lett., vol. 10, no. 6; doi: 10.1098/rsbl.2014.0235