15. Budgies catch each other’s yawns.
Budgerigars, or budgies, a common parakeet, are the only known bird species susceptible to contagious yawning. While humans, dogs, chimps, lab rats, and a few other creatures have all been known to catch each other’s yawns, budgies are the first non-mammal species observed exhibiting the behavior. Many scientists believe the unconscious, instinctual response may be a primitive way of showing empathy, or it might be a sign of group alertness.
A version of this story ran in 2016; it has been updated for 2023.