Why do koalas sleep so much?

Answer: Low-energy eucalyptus diet

Low-energy eucalyptus diet ✓ — Correct! Energy conservation! Koalas sleep 18-22 hrs/day due to diet. Eucalyptus leaves: (1) Low nutritional value—little protein/energy. (2) Toxic compounds require energy to detoxify. (3) Tough, fibrous—slow digestion (takes days). Slow metabolism compensates—conserve every calorie. Also: small brain (saves energy—unusual for mammals). Mostly nocturnal feeding. Trade-off: safe niche (eucalyptus toxic to most animals—little competition). Specialized gut bacteria detoxify leaves. Energy budget so tight that activity limited!

Their brains need extra rest — Wrong. Koala brains are actually quite small for their body size—they don't need extra rest for brain function. They sleep so much because their eucalyptus diet provides minimal energy.

They hibernate year-round — Wrong. Koalas don't hibernate—they're active daily, just for very short periods. Their extended sleep is due to their low-calorie eucalyptus diet, not seasonal dormancy.