Koalas rarely drink water because eucalyptus leaves provide nearly all the hydration they need.

The term 'koala' is thought to originate from the Dharug language, an Australian Aboriginal language, where the word 'gula' or similar variations translate to 'no water.' This reflects the animal's remarkable physiological adaptation to its specialized diet. Eucalyptus leaves consist of approximately 50% to 55% water, which is sufficient for the koala's daily needs under normal climatic conditions.Koalas have an exceptionally low metabolic rate—roughly half that of most other mammals. This slow metabolism allows them to retain water for longer periods and reduces the need for frequent replenishment. They also possess specialized kidneys that are highly efficient at concentrating urine, further minimizing water loss from their bodies.Research published in the journal PLOS ONE in 2020 highlighted a previously overlooked behavior called 'stem-licking.' During rainfall, koalas lick water running down smooth tree trunks, which supplements their intake without requiring them to descend to the ground. This behavior is critical for survival during the increasingly frequent heatwaves in Australia.When temperatures exceed 35°C (95°F), the water content in eucalyptus leaves can drop significantly. During these periods, or during prolonged droughts, koalas are forced to seek out standing water sources. This vulnerability was notably documented during the 2019–2020 'Black Summer' bushfires, when dehydrated koalas were frequently seen accepting water from humans.