Do Fish Sleep? And Other Questions on Animal Sleep Answered

Sleep is fundamental to our survival, and that goes for animals, too. If you’ve ever wondered: ‘when do fish sleep’, ‘what animal sleeps the most’, and even ‘if animals sleep at all’ – then you’re not alone.

Without the night-time comforts we take for granted, animals have to work with their surroundings and their anatomy to get the rest they need.

Interestingly, the way animals sleep varies hugely across species with some showing similar traits to our own habits and others not so much.

Let’s find out more…

Which animals sleep a lot?

On average, humans need around 8 hours of sleep a night, and while some of us need more sleep than others, we’ll never be able to compete with a few of the longest sleepers of the animal kingdom.

Koalas love their sleep! Snoozing up to 22 hours a day, they need all that sleep to help them digest the toxins found in eucalyptus leaves.

They’re not the only ones who sleep long hours to preserve energy either. Brown bats can sleep around 19 hours a day, allowing them to come out at night full of energy for hunting insects.

The giant armadillo, North American opossum and python are also amongst some of the longest sleepers, with your cat or dog following closely behind.

Which animals sleep standing up?

Sleeping whilst standing up may not seem appealing to most of us, but this is exactly what horses, zebras, elephants, and even cows do. But why?

Larger animals are slower to get to their feet in a hurry, so in the case of an unwanted guest, these guys need to be ready to go.

The legs of these animals have what is known as ‘stay apparatus’. This is where the ligaments and tendons lock the joints with minimal effort from their muscles, enabling them to doze whilst standing.

Whilst animals with this handy natural tool can sleep lightly when standing up, they’re not able to achieve deep sleep (REM sleep) in this position. Lying down enables them to get some quality sleep, but doing so in the wild has its risks.

Sometimes a stand-up snooze is far safer.

Which animals sleep underwater?

Do fish sleep? If the film, ‘Finding Nemo’, is anything to go by, then it’s a yes – albeit fish sleep is very different from how the rest of the animal kingdom do it.

Unlike humans who completely switch off whilst sleeping, fish and marine mammals only switch off half of their brains when asleep, allowing them to stay alert at all times.

A sleeping fish is fairly hard to spot as they’ve got no eyelids to close and they still need to move to ensure they get the oxygen they need. Some types of fish, like the clownfish, hide in coral reefs, whilst the slightly more peculiar parrot fish creates a mucus bubble around themselves as a form of protection.

Larger marine life such as whales and dolphins have been known to rest in the water vertically or horizontally, or to catch their 40 winks whilst swimming slowly next to another.

Which animals sleep the least?

We’ve had the longest sleepers, now it’s time for the animals that don’t sleep, or hardly at all.

Giraffe’s, most notably, get by on only a few hours of sleep a day. For similar reasons to other large animals, they’re at risk from predators when they lie down. Instead, they opt for multiple short naps throughout the day.

Horses, deer, elephants, and dolphins are also known for needing very little sleep, too – perhaps an inherent trait for all animals weary of predators.

Even more impressive are birds like the alpine swift, who can fly continuously for up to 6 months at a time when they’re migrating. This means no stopping for sleep!

These types of birds are thought to glide through the air for short periods of time to preserve their energy and even nap.

Want to know more about sleeping animals? Here are some more fascinating facts about how animals