Have you ever read the children’s book Everyone Poops? Of course you have. It’s a seminal book that inverts your concept of pooping as a child. But even if you’ve read the book, you’ll be shocked to learn the pooping habits of African hippos.
Two American scientists recently published a study via Nature Communications titled “Organic matter loading by hippopotami causes subsidy overload resulting in downstream hypoxia and fish kills.” Translation: These hippos be pooping so much it’s suffocating and murdering the fishies.
Within the vicinity of Tanzania and Kenya’s Mara River, hippopotami graze in the grasslands at nights and return to the river during the day to stay cool and avoid sunburn. “As they wallow, they constantly urinate and defecate,” science journalist Ed Yong so eloquently wrote in The Atlantic.
If that makes you giggle, you should read the scientific study, initially highlighted by Gizmodo:
The hippopotamus (Hippopotamus amphibius), which has long been recognized as an ecosystem engineer through its grazing and wallowing activities, transports massive amounts of organic matter and nutrients from terrestrial grazing lands into aquatic ecosystems through egestion and excretion in East Africa, there are an estimated 70,000 hippopotami, potentially loading 52,800 metric tons year−1 of organic matter directly into aquatic ecosystems. Laboratory and field studies suggest that these inputs may strongly influence aquatic biogeochemistry and food webs.
As noted, you weren’t prepared for the amount of pooping involved in this story, were you?
When the hippos “constantly defecate” it collects at the river bottom, speeding up the decomposition process and robbing the river of its oxygen. Heavy rains can cause what scientists describe as “flushing flows,” causing the oxygen-deprived river water to rage downstream. That water pooling downstream is what suffocates and kills the fish.
You have to appreciate just how out of their way scientists went to ensure this hypothesis.
The duo went out of their way to confirm this idea. They added hippo poop to bottles of water and demonstrated that oxygen levels fall. They added poopy water to “experimental streams”—long trays designed to simulate a flowing river. But they still craved a more realistic experiment. “We were talking about ways of how we could create a flood through a pool, and some other researchers said: Why don’t you build a small dam?”
Inspired, the duo used sandbags to block off the water supply to a nearby pool that’s in hippo territory but not frequented by the animals. A Maasai fixer connected them to a guy who had a large truck, another guy who owned two huge 4,000-liter tanks, and a third guy who owned a large wastewater pump. With all of that, the team transferred 16,000 liters of soiled hippo water into their artificial pool. And when they released the sandbags, they found that oxygen levels did indeed plummet in the water downstream.
Again, You were not prepared for the poop levels of this story, were you?
Here’s what may surprise your human brain: All of this could be the functioning of a healthy ecosystem. In fact, scientists discouraged any human intervention in this process. This poopy circle of life “challenges our notions of the reference state of rivers in the absence of human influence.” Look, sometimes fishies need to suffocate from massive amounts of crap. Our puny human brains need to learn to accept that.