Roaring or yawning? Incredible sleepy wildlife moments
Why do some animals yawn?
Yawning occurs in just about every vertebrate animal. And yawning in many animals, including birds, is frequently associated with drowsiness. But not exclusively.
For example, while most species of birds open their beaks in a fair impression of a mammalian yawn, no one has yet proven whether or not this "jaw stretching" also regularly includes the inhalation and exhalation of air. Some species of penguin employ yawning as part of their courtship ritual. And for other noisy and gregarious birds like parrots, yawning serves as a social signal.
With primates, yawning is a sign of sleepiness. But a yawn can also convey complex social messages, for example, to demonstrate friendliness and aggression. Furthermore, yawning can be contagious.
In humans, yawning is demonstrably contagious, as it is easily triggered by seeing, hearing, reading, or simply thinking about another individual yawning. Similarly, with primates, and especially monkeys, yawning is contagious between individuals.
Anyone who owns a pet dog will know that canines often yawn after seeing people yawn. Cats also demonstrate this kind of empathy towards their owners. Cats and dogs, however, also advertise their need for sleep, and will yawn simply because they are genuinely tired and in need of rest.
In the animal kingdom, many animals yawn, even creatures as diverse as fish and reptiles. Indeed, some snakes yawn after a good meal (in fact, it’s a way of realigning their jaws after eating). Siamese fighting fish yawn to show aggression.
A 2014 study suggested that the reason humans yawn has nothing to do with tiredness of boredom. Instead, we yawn in order to cool down our brains, thus enabling us to think more clearly. In hot temperatures, yawning increases both the heart rate and blood flow while delivering a sizable shot of air to the head, cooling the blood in that area.
But does that have the same effect on animals?
Well, science can’t agree.
Cooling the brain is one theory. Another is that when oxygen levels are low or carbon dioxide builds up in the body, an animal will yawn to recharge its lungs with a super-capacity intake of breath.
The truth is that no one really knows why some animals yawn, or appear to do so. But one thing is certain: when it's time to snooze, there are certain members of the animal kingdom that look absolutely stunning in their state of semi-slumber.
Click through this gallery for some wonderful sleepy wildlife moments.