As anyone who’s ever prowled Instagram for updates on Fiona the very famous hippo knows, there are a million and one reasons to love the common hippopotamus. They are mammals, but semi-aquatic ones, so they can submerge themselves for as long as five minutes without coming up for air. Accordingly, the ancient Greeks named them “river horse.” And, a new study published Wednesday in Science Advances found, hippos “play a key role in Si cycling as a terrestrial-aquatic pump.”
Hippos may look like smiley, slimy 4,000-pound friends just waiting to be made. But they’re among the most ferocious creatures on Earth, attacking crocodiles, lions, humans, and anything else that gets in their way. Despite this ferocity, the common hippopotamus is mostly a herbivorous species. In addition to some light cannibalism, individuals munch on approximately 80 pounds of plants every day, most of which they defecate into the waterways they spend their day wading around in.
As a result, hippo poop is a plentiful resource. So plentiful, in fact, that groups of hippos have been known to kill all of the fish in their immediate environment with their abundant feces. But according to this latest study, these prodigious bowel movements aren’t all bad. Rather, hippo intestines may be a crucial pipeline for the element silicon (Si), which they consume in their earthly diets and excrete through their underwater doo-doo.
To study silicon cycling, University of Antwerp biologist Jonas Schoelynck and his colleagues analyzed samples from the Mara River, which runs through the Maasai Mara National Reserve, a savannah in Kenya. The authors compared the chemical composition of the water with the local hippo population’s daily habits. They concluded that this poop introduces 0.4 metric tons, or roughly 800 pounds, of silicon into the Mara River every day. That’s about 76 percent of the river’s entire downstream silica flow. Other sources include soil erosion (the hippos themselves get their silicon by eating the roots and dusty leaves of plants) and the contributions of other, less legendary poopers.
Silicon may be famous as an iPhone ingredient, but its role in nature is just as important as its position in a microchip. The element feeds the growth of a microalgal species called the diatom. Together these single-celled organisms extract carbon dioxide from the atmosphere and convert it into oxygen. While estimates vary, diatoms are responsible for fixing at least 20 percent of the oxygen available on Earth. Without this microalgae—and the silicon shells it lives inside—you’d have a much harder time taking your next breath. Diatoms also form the base of the food chain, feeding small animals like mussels, crabs, and snails, which in turn feed bigger animals like otters, turtles, and even humans.
The silicon emanating from Mara River hippos eventually makes its way to Lake Victoria, the world’s largest tropical lake. There one finds a rich and varied ecosystem, populated by swamp-loving sitatunga antelopes, Nile crocodiles, rainbow-colored cichlid fish, and shoebill storks—all of them depending, in ways big and small, on some periodic table product pumped out of an almost-hairless and totally murderous giant’s butt.
What a wonderful world.