Koalas have developed one of the most extreme sleep patterns in the animal kingdom as an adaptation to their specialized diet.
These Australian marsupials sleep between 20-22 hours a day, dedicating only 2-4 hours to activities such as feeding, socializing, and moving between trees.
Their extreme lethargy is due to eucalyptus leaves, their only food, being extremely low in nutrients and hard to digest. The leaves contain toxic compounds that require a lot of energy to be processed by their specialized digestive system.
A koala's digestive process can take up to 200 hours, during which its metabolism slows down considerably. Its brain, one of the smallest in proportion to the body among mammals, also consumes less energy. Sleeping so much allows them to conserve the vital energy needed to survive on such a nutrient-poor diet.
Source: Australian Wildlife Research
