– Fact no. 1:
Animals that don’t have eyelids, such as snakes and fish (including sharks), will sleep with their eyes wide open – as such, due to the absence of eyelids, it’s very difficult (if not impossible) for the inexperienced eye to know if a snake or a fish is genuinely sleeping.
– Fact no. 2:
A hibernating animal will spend the entire winter sleeping unabated, never bothered by any noise (however loud) happening in the outside world – one can almost call this a “constant state of unconscious sleep”, which only stops at the arrival of spring. This category includes animals that either have zero tolerance of the cold – such is the case with cold-blooded reptiles (snakes and lizards), insects (bees, earthworms, wasps and the like) and some mammals like bats and rats –, or simply wish to avoid struggle and starvation amidst food shortage in the snowy environment – such is the case with hedgehogs, badgers, dormice, ground squirrels, etc…
Bears are an exception to this rule. Sure, when winter is here, they cease all activities and sleep until the warm spring arrives – in the process, these animals slow down their metabolism and survive on their fat reserves, which they gathered from eating incessantly during the previous summer –; and yet, nothing prevents a bear from waking up and becoming active while its territory is still covered in snow, particularly whenever it’s picked up the scent of approaching creatures or a nearby animal carcass, or it’s been awaken by unwelcome noise (so bears are pretty much light sleepers).
– Fact no. 3:
Unlike humans, dogs don’t follow a binary sleeping pattern. Instead, their everyday pattern is spent as follows: 20% awake and active, 30% awake and inactive (just lying around without necessarily sleeping), and 50% asleep both during the day and at night (up to 12–14 hours).
– Fact no. 4:
In contrast with us humans who sleep for 6–9 hours at night, many animals like lions, sloths and koalas may rack up enough sleep for around 18–20 hours! Indeed, the best thing these creatures do is doing nothing for most of the day, all for the purpose of conserving energy – worthy of making some of us lazy humans look active in comparison…
– Fact no. 5:
A lot of animals engage in something called “unihemispheric slow-wave sleep” – meaning the practice of dozing off with one brain hemisphere at a time, while simultaneously leaving one half of the brain active and on the lookout for potential danger (in other words, literally keeping an eye out while sleeping). Dolphins and whales are the primary examples, but other creatures like crocodiles, bats and some birds do it as well.
– Fact no. 6:
Elephants spend 20 hours a day eating, and only 4 hours at night sleeping! Talk about a lot of time spent eating…
