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Here Come the Autonomous Hippo Poop Drones

Disguised as crocodiles, they test river water quality. Obviously.
A hippo out of water. Image via Gusjer.

Autonomous airboats designed by Carnegie Mellon roboticists were deployed in Kenya's Mara River this spring. Their mission? To find out just how badly hippopotamus dung is contaminating the water. Each hippo in the region dumps about 22 pounds of wet dung into the water daily, and there's about 4,000 of them using the river as a latrine. Freshwater ecologists have long suspected that hippo poop has been influencing mass fish die-outs downstream, but have been unable to get close enough to the animals to find out.

As if this story isn't weird enough, the team's three airboats were cleverly disguised as crocodiles at the suggestion of a local Maasai guide. For the most part, the camouflage worked, though there was one exciting exception in which an enormous hippo took umbrage at the off-putting “crocodile” gliding through its territory. The animal gave chase for a short while, but was forced to halt once it reached deeper water, allowing the spy boat to pull off a narrow escape.

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"Just seeing that 2½-ton animal going after the boat—everyone was holding their breath," Paul Scerri, a participant in the CMU study, told NBC News. "It was definitely the most amazing thing I've seen." Thankfully, the tense confrontation was caught on video, then further enhanced with the Jaws score (the action gets good around minute 1:30).

The climactic chase via YouTube.

Indeed, the reason these autonomous spies were deployed instead of manned boats is because hippos are such testy creatures. Despite their rolly poly appearance, they kill more people than any other large animal in Africa.

“Hippos are very territorial and aggressive and have been known to attack boats," Yale researcher Anna Subalusky explained in the team's press release. "We have to work with armed rangers when we get in the river anywhere, but we would never be able to get into a hippo pool."

The airboats, on the other hand, were able to access 10 different pools without much interference from the animals. They were deployed over a three week period this past March, and collected a sizable chunk of data about the hippo hangouts. In addition to having cameras mounted on them, the boats were equipped with sonar sensors, thermometers, and devices for reading oxygen levels and electrical conductivity.

The team's data has yet to be analyzed, but their hypothesis is that hippo waste ends up accumulating in large clumps when water levels are low. Dung-eaters chow down on those sediments, which leaches oxygen out of the water. When the river runs high again, the dung is “flushed” out of the hippo pools, causing oxygen levels to crash downriver. This disruption may be responsible for killing off fish further along the Mara.

Fortunately, the CMU team was able to measure these pools both before and after one of these flushing events, which should provide valuable insight into the poop/fish dynamics of the river. Though there's still plenty of work to be done, the researchers should pat themselves on the back for now. After all, they successfully infiltrated the ranks of one of the most deadly animals in Africa using poop-hunting spy boats. That is an accomplishment for the ages.