Science & Technology
6:00 am
Mon June 9, 2014

CMU Spin-Off Technology Allows Research of Hippo-Infested Waters

Hippos in Kenya's Mara River give chase to a Platypus robotic boat that is disguised as a crocodile. The boat was able to out-swim the hippos.
Credit Platypus LLC / http://crw-cmu.blogspot.com/2014/03/hakuna-matata.html

Technology from Carnegie Mellon University Robotics Institute spin-off Platypus LLC has gone where no man has gone before. Small, autonomous airboats were sent to Kenya to monitor water quality in hippo pools on the hippo-heavy Mara River. Researchers want to know how the animals are affecting water quality, but they couldn’t get into the pools to collect samples.

“Hippos are extremely dangerous animals, and that’s ignoring the crocodiles that are hanging out in the same river,” said Paul Scerri, Platypus president, “so when they [researchers] saw our technology they asked us if we could come down and run robots around.”

The boats were disguised to look like crocodiles, which the hippos tolerate, and were sent onto the water.

“We outfitted them with oxygen sensors that we can raise and lower and some depth-measuring equipment that would measure the softness of the bottom of the river,” said Scerri. “There was at least one day that the researchers counted 140 hippopotamus in the river where we had the boat.”

At issue is the fact that the river is used, essentially, as the hippos’ toilet. They leave the river to eat, then return and deposit their waste as they wallow throughout the day. An estimated 4,000 hippos use the river, and researchers are concerned that this is contributing to water quality problems, especially in periods of low flow.

Researchers launch one of the crocodile-disguised boats onto the Mara River.
Credit Platypus LLC / http://crw-cmu.blogspot.com/2014/03/hakuna-matata.html

Researchers said each hippo produces about 22 pounds of wet dung each day. When the river is running high, the dung moves down the river, but during low flow periods, the dung settles to the bottom of hippo pools. There, bacteria feed on it and consume oxygen; then during high flows, when the water is flushed downriver, it causes oxygen levels to crash and fish kills can result. That’s the hypothesis, but until now, scientists haven’t been able to go get into the water to collect samples; the robotic boats could.

“The Robotics Institute at Carnegie Mellon, from which we spun out, used to have a motto that ‘robots do dull, dirty and dangerous things,’” said Scerri, “and taking hundreds and hundreds of samples from a river full of hippopotamuses and hippo dung seems to fit that motto almost perfectly.”

The boats were deployed in 10 different hippo pools. The data are still being analyzed and are unpublished, but researchers were able to measure several pools both before and after a flushing event, so they said they are hopeful the results will be comprehensive.

Beyond hippos, this technology could potentially change what is known about some bodies of water.

“It’s really difficult to get information about live bodies of water or of large areas over long periods of time,” said Scerri. “Our technology, we think, lowers the cost of collecting this information. So something that cost $10,000, we can now do for $100.”

The boats supported the work of researchers Amanda Subalusky, Christopher Dutton and David Post of Yale University and Emma Rosi-Marshall from the Cary Institute of Ecosystem Studies. They have been studying water quality on the Mara since 2008.