Wild koalas have adapted a bizarrely cute method of staying hydrated by licking rainwater as it runs down smooth tree trunks and foliage during rainfall. Footage of the novel behavior has been analyzed for the first time in an attempt to better understand the unique life history of one of Australia’s most charismatic creatures.
Koalas often live in dry environments that make gathering water a particularly dangerous task for the tree-climbing marsupials, particularly as 2019 was the hottest and driest year in Australian history. Extreme temperatures fueled devastating bushfires that swept the continent, believed to be responsible for the destruction of more than one-fifth of the nation’s forest, and the deaths of over 1 billion animals. Among those injured include dozens of wild koalas, at least 49 of whom spent months in recovery before being released into the wild in April.
Many parts of Australia are still seeing below-average rainfall that may pose a threat to the heat-sensitive marsupials. Over the years, conservationists have set up artificial water stations during periods of water scarcity, and scientists note that understanding how koalas adapt during periods of intense heat and drought could inform future conservation efforts.
"For a long time, we thought koalas didn't need to drink much at all because they gained the majority of the water they need to survive in the gum leaves they feed on," said study author Dr Valentina Mella in a statement. "But now we have observed them licking water from tree trunks. This significantly alters our understanding of how koalas gain water in the wild. It is very exciting."
Researchers from the University of Sydney collected video footage from citizen scientists and independent ecologists between 2006 and 2019 from two regions in Australia. A total of 44 observations were recorded of wild koalas licking water as it runs down a tree trunk immediately after rainfall for long periods of time. One observation of an adult female with a joey drank for 15 minutes straight while another adult male drank for more than half an hour, according to findings published in the journal Ethology.
"This type of drinking behavior – 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," said Mella.
"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."
Koalas were seen licking the wet surfaces of branches and tree trunks even when pooling water was available, suggesting that it is likely koalas use this method to drink water naturally. Given their unique way of life, such behavior has been difficult to capture in the past.
"As koalas are nocturnal animals and observation of their behavior rarely occurs during heavy rainfall, it is likely that their drinking behavior has gone largely unnoticed and has therefore been underestimated in the past," said Mella. "Our observations probably only represent a minority of the drinking that normally takes place in trees during rainfall."