What animal does not yawn?

It's not true that any animal *doesn't* yawn. Yawning is a very common behavior across many species, including mammals, birds, reptiles, and even fish!

While the exact reasons for yawning are still debated, it's likely related to:

* Regulating brain temperature: Yawning helps to cool the brain by increasing blood flow.

* Increasing alertness: Yawning can help to wake up the brain and improve alertness.

* Social signaling: Yawning can be a way for animals to communicate their boredom, tiredness, or even stress.

So, while the specific reasons for yawning vary across species, it's a behavior that's shared by a wide range of animals.