How Do Whales Sleep?
Unlike humans who can breathe automatically while sleeping, whales must consciously breathe. This raises an interesting question: how can they sleep without drowning?
Unihemispheric Sleep
Whales have evolved a remarkable solution called unihemispheric slow-wave sleep (USWS):
- One half of the brain sleeps at a time
- The other half stays awake
- They switch sides periodically
- This allows them to surface and breathe
Different Whale Sleep Patterns
Sperm Whales
- Sleep vertically near the surface
- Sometimes in groups, floating like logs
- Sleep in short bursts of 10-15 minutes
Humpback Whales
- Rest horizontally near surface
- Slow their metabolism dramatically
- Can hold breath for 30+ minutes while resting
Orcas
- Swim slowly while sleeping
- Often rest in groups
- Mother orcas don't sleep for first month after birth
How Long Do Whales Sleep?
| Species | Daily Sleep | Method |
|---|---|---|
| Sperm Whale | 7% of day | Vertical floating |
| Humpback | 6-8 hours | Near-surface rest |
| Orca | ~5 hours | Slow swimming |
| Beluga | 4-6 hours | Various positions |
Why Half-Brain Sleeping?
This adaptation serves multiple purposes:
- Breathing: Must surface consciously
- Predator awareness: Stay alert to threats
- Thermoregulation: Keep moving in cold water
- Calf protection: Watch over young
- Social maintenance: Stay with pod
Do Baby Whales Sleep?
Remarkably, newborn whales and their mothers barely sleep for the first month:
- Calves must keep moving for warmth
- Mothers stay vigilant for predators
- They gradually develop normal sleep patterns