While humans typically need 7–9 hours of sleep per night, some creatures in the animal kingdom take rest to an extreme level, sleeping for up to 90% of the day.
But why do some animals need so much sleep, and what can we learn from these extreme sleepers? This article explores the species with the longest sleep durations and the science behind their extraordinary habits.
Animals That Sleep 90% of the Day
Several animals are known for their extreme sleep durations, often exceeding 20 hours per day:
1. Koalas
- Sleep up to 22 hours per day
- Diet consists mainly of eucalyptus leaves, which are low in calories and hard to digest
- Extra rest conserves energy and aids in digestion
2. Sloths
- Sleep 15–20 hours per day, with some reports up to 22 hours
- Slow metabolism and low-calorie diet require prolonged rest
- Minimal movement reduces energy expenditure
3. Bats (Especially Little Brown Bats)
- Can sleep 19–20 hours daily
- High-energy nighttime activity means daytime rest is essential for recovery
- Sleep conserves energy and maintains body functions
4. Opossums
- Sleep 18–19 hours per day
- Nocturnal lifestyle with long daytime sleep helps avoid predators and conserve energy
Why Do Some Animals Sleep So Much?
Several factors influence extreme sleep habits:
1. Metabolism
Animals with low-calorie diets or slow metabolisms need more rest to conserve energy.
2. Predator Avoidance
Sleeping during vulnerable times can help avoid predators.
3. Brain Function and Memory
Sleep supports memory consolidation, energy restoration, and immune function — even in animals.
4. Energy Conservation
For species like sloths and koalas, movement is minimal, and resting maximizes survival efficiency.
Do Any Humans Sleep This Much?
No. Humans do not naturally sleep for 90% of the day. Excessive sleep in humans may indicate:
- Severe illness or infection
- Sleep disorders such as hypersomnia
- Effects of certain medications or neurological conditions
Normal human sleep rarely exceeds 10–12 hours per day, even in exceptional cases like recovery from illness.
Calculate your ideal sleep duration with the Sleep Times Calculator.
Fun Facts About Extreme Sleepers
- Koalas rarely drink water; most hydration comes from eucalyptus leaves.
- Bats sleep upside down to protect themselves from predators.
- Sloths can survive in trees despite sleeping most of the day.
These adaptations show how sleep is not just about rest — it’s about survival.
FAQs: People Also Ask
Which animal sleeps the most?
Koalas are among the top sleepers, resting up to 22 hours per day.
Why do sloths sleep so much?
Their low-calorie diet and slow metabolism require extended rest to conserve energy.
Do any humans sleep 20 hours a day?
Only in extreme cases of medical conditions like hypersomnia. Normal human sleep is much shorter.
Why do bats sleep so long?
Bats are nocturnal, so they sleep during the day to recover energy for nighttime activity.
Can sleeping too much be harmful to humans?
Yes. Chronic oversleeping may be linked to diabetes, heart disease, or depression.
Conclusion
Sleeping for 90% of the day may sound unbelievable, but in nature, it’s a survival strategy for certain species like koalas, sloths, bats, and opossums. Their extreme sleep helps conserve energy, aid digestion, and avoid predators.
For humans, the lesson is not to sleep 22 hours a day — but to respect your sleep needs, aim for consistent restorative sleep, and maintain healthy sleep hygiene.
Discover your ideal sleep duration and timing using the Sleep Times Calculator to optimize your rest and daily energy.