Quirks & Quarks

Now we know how koalas drink (we didn't before)

Koalas have been observed licking rainwater as it cascades down the smooth trunks of eucalyptus trees

Koalas have been observed licking rainwater as it cascades down the smooth trunks of eucalyptus trees

An adult female koala quenches her thirst on water cascading down a tree trunk. Researchers used hoses to duplicate the effects of rain and observe koalas drinking. (Valentina Mella)
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One of the great mysteries surrounding one of Australia's  most iconic creatures - the koala - has been solved. Scientists now know how the charismatic marsupial is able to access enough water to survive.

Researchers had long been puzzled about how koalas acquired enough water. A certain proportion of their water needs must have been satisfied by the moisture in the eucalyptus leaves they feed on. 

But koalas didn't seem to exploit any other source of waters. They were only rarely observed descending from their trees in search of water in waterholes, streams or puddles.

A recent study led by Valentina Mella, a researcher in the School of Life and Environmental Sciences at the University of Sydney has revealed that koalas drink by licking water running down smooth tree trunks as it rains. 

Thirsty marsupials

Solving this mystery has not been easy because koalas are nocturnal and spend most of their time high up in tree tops. 

But from 2006 to last year, a total of 44 observations of koalas licking trees during rain, mostly by citizen scientists in two locations: the You Yangs Regional Park in Victoria and the Liverpool Plains in New South Wales. 

A thirsty koala eagerly licks the trunk of a eucalyptus tree in the rain. (Valentina Mella)

One adult female, with a joey, was observed drinking profusely and uninterruptedly for 15 minutes. An adult male drank at a steady pace for 34 minutes. Because other sources of water were readily available in nearby locations, Mella believes that this method of licking tree trunks is how koalas prefer to drink naturally. It saves the Koalas the trouble — and risk — of descending from their trees.

Surviving drought and wildfire

Recently, during Australia's severe drought, record temperatures and consequent wildfires, koalas have been approaching humans to drink out of water bottles in desperation. This is considered very unusual behaviour, and reflective of just how desperate for moisture the animals are. 

Mella is concerned that the lack of regular precipitation, as well as the loss of habitat, will have serious consequences for the koala in the future. 

Video of koala drinking from the University of Sydney

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