A neat story often repeated on the internet (thus not to sure who to attribute it to): Long time ago Hippos were land dwelling animals but the hot African sun meant they were subject to sunburn on their delicate pink ears. So they called a meeting with god. At the meeting they asked god if they could spend their days in the cool water of rivers and ponds so they could cool their hot bodies and prevent their delicate pink ears from sunburn. God, at first, was not sure about this. He was worried that the Hippos wanted to feast on the numerous fish in the rivers and ponds. The hippos protested at this assumption. So they decided to make a deal with god. If he would let them spend their days in the cool water they would several times a day open their mouths toward the heavens and show god they did not have any fish in their mouths. God thought about this proposal, after some time he agreed. So the hippos entered the water and several times a day opened their mouths to show god that they did not have any fish in their mouths. And all this time you thought hippos were yawning!
Yawns are probably a territorial and threat display
...and apparently they don't just eat cabbages as the Katzenjammer Kids of my youth...
...their canines and incisors make them at least opportunistic carnivores!
Try not to yawn while watching those images !
"What do you mean ? Only a 7 ???"
Nice rugae on my palate !
And a little splashing...
"Not only I have TMJ to die for, but how about my cervical vertebrae ?"
"Ha, can't beat that one huh ?"
"Idiot paparazzi !!! Don't cut my nose !!"
"I can do with a water lily in my mouth !"
"I lost footing !!"
"Yes !! My dental assistants also congratulates me on my clean gums !"
Hard to keep your footing when showing off
"...and my applause ??"