Researchers from Carnegie Mellon University used robots designed to look like crocodiles to study the effects of feces on the water in the Mara River Basin in Kenya.
The researchers said that the river is used as a toilet by an estimated 4,000 hippos, according to VentureBeat.
Hippos statistically kill more people in Africa every year than crocodiles do.
There was one incident in the research when a hippopotamus started to chase the robot, NBC News reported.
"Just seeing that 2 1/2-ton animal going after the boat- everyone was holding their breath," said Paul Scerri, president of Platypus LLC and associate research professor at the university's Robotics Institute. "It was definitely the most amazing thing I've seen."
The Mara River's water quality was studied for three weeks in March. The scientists believe the hippos' use of the river is responsible for the occasional deaths of fish.
They said that during periods of low flow, the hippo feces accumulate at the bottom of pools in the river. When the river rises, the feces is flushed down the Mara, leading to a decrease in oxygen levels downstream and the death of the fish, NBC News reported.
The research team looked to confirm this hypothesis by sampling water from where the hippos relaxed. To be safe, they used three remote-controlled airboats equipped with tools to collect the samples.
A local guide suggested that disguising the boats as crocodiles would help the hippos tolerate them. The team used a foam crocodile head and green fabric to disguise one of the boats. With the exception of the one hippo giving chase, the boats were tolerated most of the time, NBC News reported.
Researchers from Yale University and the Cary Institute of Ecosystem Studies were part of the team, VentureBeat reported.
The team has spent the last six years studying the Mara's water quality.
The researchers also managed to collect data on the depth of the river, the depth of the fecal deposits, and the river's quality of river before and after flushing events, NBC News reported.
If the feces is determined to be the issue, then strategies can be developed by conservationists to reduce its effect on fish downstream.
"What we can give them is one more data point," Scerri said.
