Almost all vertebrate animals, including mammals, birds, reptiles, amphibians, and even fish, experience yawning. The study of yawning is called chasmology. Yawning (oscitation) most often occurs in adults immediately before and after sleep, during tedious activities and as a result of its contagious quality.

Dogs can catch yawns from other dogs, and from humans. Like us, they can catch a yawn in person or just from seeing or hearing one. And like humans, dogs are more likely to catch yawns from people or other dogs they know, suggesting that empathy plays a role in contagious yawning for dogs too.

The mouth of a hippopotamus is scary not because of how it looks but because of what it can do. These animals are known for their wide yawns where their jaws can open to almost a full 180 degrees. The yawns are primarily used for intimidation, which makes sense considering the large animal's territorial nature.

There is evidence that yawning can help stimulate the body in ways similar to caffeine intake. Also, studies show that yawning can help reduce brain temperatures, and yawning appears to increase after abnormal thermoregulation (how the body manages temperature).