Do all animals yawn?

Not all animals yawn, if only because many large groups of animals lack the basic anatomy necessary for yawning. Tapeworms, for example, are parasitic animals that absorb nutrients through their skin, according to HowStuffWorks, and therefore lack a mouth. read more

Many insects do not yawn because their breathing mechanism is very different from that of other animals. Instead of having a central oxygen collection device — the lungs — most insects absorb oxygen from every cell in their body, which then is dissolved into fluid to carry to all the body’s tissues. read more

Not all of them yawn equally frequently, and not all in the same way or circumstances, but I have seen many mammals, some birds and a few reptiles yawning. I don't remember having seen any amphibians yawning. read more