Koalas are always sleepy because they eat eucalyptus leaves which contain a natural sedative that makes them drowsy.
Eucalyptus leaves are low in nutrition and high in fibre, requiring enormous energy to digest. Koalas spend 18-22 hours a day resting to conserve energy for this digestive process. While eucalyptus contains compounds that can be toxic, koalas have evolved special liver enzymes to detoxify them. The sleepiness results from energy conservation, not sedation.
Reception
Sources
- National Geographic: Koala Sleep REFERENCE
- PLOS One: Koala Digestive Ecology PRIMARY