Scientists have just learned that koalas lick tree trunks to quench their thirst when it rains. What biologists have long thought about koalas is changing: that they get almost all the water they need from the eucalyptus leaves they eat.
But koalas, like many animals, are likely to leak water – except from trees, as the results published today in the journal Ethology show. With fires, heat waves, and droughts affecting animals more and more, scientists have been paying close attention to how koalas stay hydrated.
“This changes our understanding of how koalas gain water in the wild. It is very exciting, ”said the lead author of the Ethology Paper and Sydney University researcher Valentina Mella in a statement.
Picture: University of Sydney
The surprising discovery was made by involving citizen scientists and independent ecologists who had observed the behavior of the koala in the wild between 2006 and 2019 at two licks per second. In total, they documented 46 cases of koalas that drank in trees during and after the rain. Koalas were recorded drinking every time observations were made in the rain. One of the reasons why scientists hadn't noticed this before is, according to Mella, that people are less likely to look for them in bad weather. The marsupials seem to prefer smooth parts of the trees, where it is easier to collect the dripping water.
Koalas are classified as endangered by the International Union for Nature Conservation, which keeps an eye on endangered species. They were devastated by massive bush fires that swept through Australia at the end of last year. Almost a third of all koalas are said to have been extinguished in the state of New South Wales, which was hit hardest by the fires.
The same hot and dry conditions that fueled the flames left koalas dry. Photos and videos of koalas approaching people to drink became viral when forest fires raged across Australia last year.
Even before the recent fires, Mella's previous research showed that climate change is making koalas thirsty. In 2017, koalas were caught on camera as they stood at artificial water stations set up by researchers – a very unusual behavior for animals that spend most of their lives in eucalyptus trees.
A koala drinking from a bird bath
At the time, Mella and her colleagues thought the behavior was due to hotter temperatures and changing rainfall patterns drying out the leaves that eat koalas. Now she and her fellow authors of the new paper think that less rainfall could be another, more direct factor that leaves koalas with less rainwater to jump off the tree trunks they call home.
Mella is currently collecting money to continue her research and set up additional drinking stations for koalas. She hopes that the drinking stations, which stand in trees, offer the koalas a safe way to cool off even if the world around them continues to warm up.