Nothing is as refreshing as a good night’s sleep. But have you ever wondered if animals really sleep? Do they too, like us, need a full night of sleep? Or are they evolutionary equipped to go on and on without sleeping?
Do Animals Need Sleep?
All animals need sleep. No animal can survive long without sleep. Sleep is an evolutionary mechanism to restore and recharge brain and body. However, animal sleep patterns are largely influenced by defence mechanism and food availability.
Animals who face predator danger tend to sleep less than those who are safe from predation. Similarly, animals who eat low calorie dense food and are larger in size, sleep less to spend more time eating and make up for their energy requirements. Two interesting conclusions emerge from these facts:
- On a general level, large herbivores sleep lesser than smaller herbivores.
- Carnivores tend to sleep more than herbivores as they don’t face predation and also their food is calorie rich.
These two factors govern the sleeping patterns and duration of animals across the animal kingdom.
Do All Animals Sleep at Night?
No. While all animals need to sleep, not all animals sleep at night. Some animals sleep during the day while others at night. The animals that sleep during the day and are awake at night are called Nocturnal Animals. These animals are active at night and rest during the day. Animals who, like us, rest at night and are active during the day are called Diurnal animals.
There is a reason why some animals are active during the day and some at night. Availability and competition for food, safety from predators and temperature are some of the factors that influence the day and night sleep patterns of animals.
Evolution over course of time has helped animals find suitable time during the day to stay active and search for food while avoiding predators. Lions are mostly inactive during the daylight, making daylight hours suitable for herbivores to stay active and graze.
What is Hibernation?
Some animals sleep for longer duration of time, spanning months, to save energy and survive climate change. This elongated sleep is called Hibernation. You must have heard a lot of stories about bear going off for a long snooze. That is actually what hibernation is – a long, deep sleep!
Many animals hibernate; some of the popular ones are desert snails, snakes, frogs, bats, hedgehogs, box turtles and chipmunks.
How/When do Different Categories of Animals Sleep?
Different classes of animals sleep differently though almost all sleep multiple times a day to meet their snooze requirements. This is influenced by their habitat, danger from predators, safety and of-course food choices.
Large herbivorous mammals like buffalo, elephants sleep for short, multiple intervals during the night. This helps them to keep safe from prey and utilise daytime for eating while their predators are mostly inactive.
Other smaller mammals, like Koala bears, sleep for much longer hours upto 18 to 20 hours a day. Prey animals like Deer, Sheep sleep lesser than their predators and are mostly found in herds or groups to increase their chances of survival, as there is safety in numbers. All these animals sleep multiple times during the night and do not take one long nap to avoid being hunted.
Apes on the other hand have a singular, longer sleep cycle much like humans. Dolphins, which are aquatic mammals, sleep with their one eye open and a part of their brain working.
Reptiles have interesting sleep pattern like humans and are believed to dream, like us, in their sleep. Most reptiles like snakes sleep while lying still and eyes open while crocodiles and lizards sleep with one eye open to watch out for safety.
Most birds sleep with their one eye open to keep them on guard from predator danger. Another interesting thing about their sleep pattern is that only a part of their brain sleeps at a time. This increases their chances of survival and is another exceptional evolutionary trick to keep them alive.
The sleep pattern for fish depends on their environment and activity level. Most fish sleep nearly motionless near the bottom or the surface of water. On the other hand, sharks sleep while swimming slowly.
Insects sleep by lying inactive. Since they don’t have eyelids, they appear to sleep with their eyes open. Many insects curl up into a ball when resting and sleeping, while others simply stay motionless.
Do Animals Dream?
It is believed that many animals like cats, dogs dream. Big dogs tend to haven longer dream cycles than smaller dogs. Rats are known to dream while sleeping and so are reptiles. Zebra Finches, the popular songbirds, are known to recite their songs while asleep. All these animals exhibit Rapid Eye Movement (REM) while sleeping which is suggestive of dreaming. Interesting Facts About Sleeping Animals
Animal’s Sleep Facts
1. Large hairy armadillos sleep unto 21 hours a day making them one of the sleepiest animals.
2. Brown bats sleep upside down and spend almost 20 hours a day sleeping.
3. Pocket mouse, the small lightweight rodents, snooze most of the day spending up to 20 hours sleeping.
4. North American opossum and pythons spend nearly 18 hours each day sleeping.
5. Pet animals like dogs and cats sleep half of the day.
6. Lions spend nearly 18-20 hours snoozing.
7. Elephants and Giraffes sleep least with just 2 hours of shuteye every day.
8. Tigers can sleep unto 16 hours a day.
9. Chimpanzee, Squirrel, monkey and baboon sleep nearly 10 hours each day.
10. Cow and sheep are light sleepers, sleeping only up to 4 hours a day.
11. Jackrabbits, Chinchillas, Ferrets are crepuscular that means they sleep both during daytime and nighttime and are most active during twilight hours.
12. Walruses can sleep both on land and on water. While sleeping on water, they stay afloat by blowing air pouches within their body.
13. Guinea baboons sleep on treetops and on their heels so they can quickly make a run if danger approaches.
14. Male malachite sunbirds puff up their bright yellow pectoral tufts as they sleep to give an impression of big eyes to a possible predator, thus scaring it away.
15. Swifts, songbirds, seabirds, and sandpipers can sleep while flying.
Animals Who Sleep With Their Eyes Open
Many animals like fishes, insects and reptiles like snakes do not have eyelids. So in that case, how do they sleep? Well! They sleep with their eyes open! It is difficult to make out if these animals are sleeping by merely looking at their eyes. So instead, look for other clues like activity level and position.
1. Snakes lie still when they are sleeping. Also they have a thin film called ‘Spectacle’ which stretches over their eyes while they catch on some sleep.
2. Honey Bees sleep by laying still and often falling sideways. Their eyes stay open, as they don’t have eyelids.
3. South American Sea Lions sleep much like Dolphins with their one eye open.
4. Blackbirds sleep with one eye open to watch out for danger.
5. Penguins sleep standing up with one eye open.
6. Fruits bats sleep with one eye open and part of their brain working like whales and dolphins. This makes them unique as a non-marine mammal to display uni-hemispheric sleep.
7. Fishes sleep with their eyes open, as they don’t have eyelids.
Funny Ways Animals Sleep
1. Ducks often sleep while afloat with one eye open to watch out for predators.
2. Sea otters float on their backs while sleeping and wrap themselves in seaweed to keep them from floating away.
3. Albatross sleep while flying.
4. Whales and Dolphins sleep with part of their brain awake to keep guard against predators and to prevent themselves from drowning. This way of napping is called uni-hemispheric sleep meaning sleeping with a part of the brain awake.
5. Horses and Giraffe catch on their naps while standing.
6. Bats and Sloths sleep upside down.
7. Gorillas make nests to sleep in.
8. Flamingos sleep while balancing themselves on one leg.
9. Many large mammals like cows, horses, and zebras can sleep while standing.
10. Desert snails can sleep (hibernate) for years before waking up for a stroll.
Whatever ways animals choose to sleep, one thing is for certain that they are super equipped to handle their snooze time and look adorably cute while napping.