The pinkness of a flamingo is a sign to potential mates about how healthy they are. They make pink feathers (with pigment derived from their diet), but those feathers bleach in the sun. So they ALSO lather themselves with a pink coloured oil. This oil is from their uropygial gland (preening gland) that all birds have (used to clean feathers). Theirs is pink! They do this more right before they try to find a mate.

The matriarch of the elephant herd will make a specific rumble that tells the herd that it's time to move on. It has also been found that in tight-knit male groups (which is funky because male elephant groups are usually considered quite loose/not very steady). 

Hippos are very noisy and territorial. They will make loud calls that echo down rivers. If they hear a hippo that isn't familiar, they react strongly. 

Their teeth are normal sized, except the roots; the parts of the teeth that are inside the gums are smaller than other cats of similar size. This is a way for them to increase their nasal cavity which helps them breathe more efficiently and therefore run just that much faster. It also means they aren't great at fighting because their teeth are more likely to fall out. 

Hyenas are very social animals and a lot of their communication with each other is actually through facial expression.