Koalas sleep for around 18 to 20 hours every day, making them some of the sleepiest mammals on Earth.
This unusual lifestyle is mainly linked to their diet. Eucalyptus leaves contain very little energy, are difficult to digest, and contain compounds that are toxic to most other animals.
Koalas have evolved a specialised digestive system to process these leaves, but extracting enough nutrients takes considerable time and energy.
When they are awake, they spend much of their time feeding, grooming, moving between trees, and interacting with other koalas.
They are mostly solitary animals and usually come together during the breeding season.
Male koalas become more active during this period, travelling between trees and searching for females.
They also produce remarkably deep, loud bellows that can travel hundreds of metres through the forest. These calls help attract females and warn rival males.
