Sleep is essential for life, but some animals spend most of their lives snoozing.

Adult humans need seven hours of sleep per night, according to the American Academy of Sleep Medicine and National Sleep Foundation. We can go 11 days without it.

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According to research, that’s on the light side. Mammals tend to sleep between three and 20 hours per day.

What regulates daily sleep requirement is unknown, but some researchers have put forth the idea that animals with larger bodies and brains need more hours of feeding per day, which is incompatible with a large sleep requirement.

For these 12 animals, life is but a dream.

Cats – 12 to 16 hours

Sloths in captivity – 15+ hours

Tree shrews – 15.8 hours

Owl Monkeys – 17 hours

Pythons – 18 hours

North American Opossums - 18 hours

Tigers – 18 hours

Brown bats – 19.9 hours

Male lions – 20 hours

Pocket mice – 20.1 hours

Large hairy armadillos – 20. 4 hours

Koalas – 22 hours