Hippos are surprisingly fast on land - they can run at about 30 kilometres per hour over a short distance, faster than most people can sprint. Despite their huge size, they are plant-eaters. At night, they leave the water to graze on grass, sometimes walking several kilometres to find enough food, then returning to the river before dawn.
A hippo's skin releases a reddish, oily liquid that acts as a natural sunscreen and moisturiser. Scientists once thought it was blood, but it is actually a special skin secretion that protects hippos from the fierce African sun and helps heal small cuts. You could say hippos invented sunscreen long before people did.
The Sélingué reservoir in southern Mali - created by a dam on the Sankarani River - has become an important sanctuary for hippos. Local guides take visitors out in small boats to watch hippos bobbing in the water, yawning, splashing and occasionally honking at each other. The pool is a peaceful place full of birdsong and the rumble of hippo calls.