HIPPOPHOTOMUSTS

The hippo photos that everyone wants are the fight and the yawn. Hippos spend most of the day sunbathing in the fierce African sun (against which they secrete their own hippo suntan lotion, incidentally). To get the shots, you'll want to be watching them at dawn or dusk. Which is when the light is at its best, anyway.

Hippos fight mostly over territory. Full-on battles are relatively uncommon - hippos live at close quarters to each other, often in numbers, and since each hippo has a pair of twelve inch long lower incisors at its disposal, regular serious aggression would be counterproductive. But skirmishes are quite common. They happen fast and with little warning, though, and most will be over before you've reacted. Look for big male beachmasters squaring up to each other as a prelude.

At dawn, the hippos return to the safety of the water after a night spent grazing, and gather in their pods. Re-entry into the water tends to be along favoured routes, and as such, males may have to pass in close proximity to beachmasters who are already in position. This 'running of the gauntlet' can allow the photographer to anticipate the skirmishes, so keep your lens trained on the beachmaster as other hippos enter the water.

Which brings us to the yawn. Hippos yawn as a threat display, so watch the males in particular when other animals from outside the pod approach too close. 

The other reason- I've heard - is that it actually is a yawn, for the same reason that we do it. In that they've lain around all day, and as evening approaches and the time comes to leave the water, the hippo needs to reoxygenate its muscles in order to drag its vast carcass onto land and walk around. It makes sense; certainly, the time to observe yawning (non-threat variety) is close to sunset.