After a night of foraging, a lone hippo heads back to his pool.
But hunters have spotted him.
Despite his size, he's vulnerable on land.
Water is his sanctuary.
He owns this bend in the river.
It's where his pod gathers to breed and bring up their young.
Key to the hippos' survival is communication throughout their watery domain.
Eighty percent of hippo calls happen underwater.
It's the glue that holds the pod together.
Their fatty necks act like resonators, amplifying their grunts so they can be heard up to a kilometer away.
