Surprising new detail about koalas

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Scientists are one step closer to understanding how koalas drink after a new study of the iconic marsupial.

Previously it was thought koalas get most of the water they need from the eucalyptus leaves that form the bulk of their diet.

Koalas don’t drink much but they do eat around half a kilo of eucalyptus leaves daily, and the moisture in these leaves account for about three-quarters of the liquid they need.

Due to years of evolution, koalas have adapted to their native climate.

Compared to other similar sized mammals koalas have evolved to urinate and sweat less, retaining more water.

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Koalas are mostly active at night meaning some of their behaviour is rarely witnessed.
media_cameraKoalas are mostly active at night meaning some of their behaviour is rarely witnessed.
Koalas might get more of their water from licking trees than initially thought.
media_cameraKoalas might get more of their water from licking trees than initially thought.

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Koalas have famously been seen drinking from water bottles held by firefighters and cyclists, but this is considered rare and something koalas only engage in during extreme situations such as bushfires and prolonged drought.

They’ve also been reported drinking from waterholes in the wild as well as things like bird feeders in people’s yards.

But a new analysis of koala behaviour in national parks in Victoria and New South Wales have shown another way the marsupials hydrate: by licking the trunks of trees.

University of Sydney’s school of Life and Environmental Sciences Dr Valentina Mella studied 46 observations of koalas licking water off tree trunks, collected by citizen scientists in Victoria’s You Yangs Regional Park and Liverpool Plains in NSW between 2006 and 2019.

Some of the observations include one adult male koala steadily drinking off a tree for more than half an hour.

Koalas likely drink more off tree trunks after rain as water flows down.
media_cameraKoalas likely drink more off tree trunks after rain as water flows down.
Sometimes koalas will pass up other water sources in favour of tree trunks.
media_cameraSometimes koalas will pass up other water sources in favour of tree trunks.

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Koalas were also seen opting to lick water off trees even when there was freestanding water nearby.

Dr Mella thinks the licking behaviour has gone unnoticed until now because of their sleep patterns.

“As koalas are nocturnal animals and observation of their behaviour rarely occurs during heavy rainfall, it is likely that their drinking behaviour has gone largely unnoticed and has therefore been underestimated in the past,” Dr Mella said.

“Our observations probably only represent a minority of the drinking that normally takes place in trees during rainfall.”

Dr Mella said the observations were “very exciting”.

“This significantly alters our understanding of how koalas gain water in the wild,” she said.

A koala in Belair National Park drinks rain off the road following bushfires in South Australia. Picture: Brad Fleet
media_cameraA koala in Belair National Park drinks rain off the road following bushfires in South Australia. Picture: Brad Fleet
A koala drinks from a bird bath in Lorne, Victoria.
media_cameraA koala drinks from a bird bath in Lorne, Victoria.

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The study was recently published in peer-reviewed behavioural biology journal Ethology.

Dr Mella said the research showed the importance of preserving koala habitats to protect the vulnerable species, but more work needed to be done to investigate whether water should be supplemented in koala habitats.

“This type of drinking behaviour – licking tree trunks – relies on koalas being able to experience regular rainfall to access free water and indicates that they may suffer serious detrimental effects if lack of rain compromises their ability to access free water,” Dr Mella said.

“We know koalas use trees for all their main needs, including feeding, sheltering and resting. This study shows that koalas rely on trees also to access free water and highlights the importance of retaining trees for the conservation of the species,” she added.

As many as ten thousand koalas, a third of the total population in NSW, are thought to have died during the devastating summer bushfires.

Some koalas that survived are now suffering long deaths through dehydration and starvation after fires burned through their habitats, destroying the trees that provided their shelter, food, and as we now know, their water too.

Originally published as Surprising new detail about koalas