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Hippos keep the Lower Zambezi in check ©Heinrich van den Berg, Chongwe River Camp

RIVER DOCTORS

Hippos play a vital role in our ecosystems, as they help the ecology of rivers and dams. Given the number of hours that a hippo family spends in the water, it is understandable that a lot of dung is deposited on a daily basis. And this dung is filled with nutrients that benefit the other inhabitants of the river - namely the fish, insects and terrapins, which coexist with the hippos.

   Mzima Springs in Kenya is a case in point. These are crystal-clear natural springs, which are naturally lacking any nutrients as the water is filtered through volcanic lava. But luckily, over 60 hippos are giving life to the springs. They literally pump hundreds of kilogrammes of dung back into the water, which in turn lays the foundation for other lifeforms to thrive. The hippo basically creates a compost heap. When the dung is deposited, thanks to its consistency and temperature, much of the goodness in the grass remains. Snails can feed on it, then birds feed on the snails, and crocodiles feed on the birds.

   Hippos also create regularly used paths that slope into the river. When the rains come, the mud and dirt washes into the catchment, and more nutrients end up in the waters thanks to these walkways.

   Furthermore, they help to maintain ecosystems by cropping grass to a very short height when they graze. As a result, they act as nature’s firemen, creating fire breaks by cutting swathes of grass in areas and stopping annual fires from obliterating all the vegetation.

   The hippo's large size and continuous movements also help to open up thickly reeded sections in rivers and wetlands, which helps the channels to flow better. This is best illustrated as you fly over Botswana’s Okavango Delta, where the hippo (and elephant) paths create channels for the annual floodwaters from the Angolan highlands to spread far and wide. If it were not for these two ecosystem engineers, many floodplains would shrink in size as channels silt up and don’t permit water to flow through.

   So from composting to fire prevention, it is clear that a hippo has many important roles in the wild.