Can a robotic boat tell us what's at the bottom of a hippo pool?

What happens inside of a hippo pool? Is it deep with a hard bottom, because the hippos are always wallowing out the mud and sediment? Or is it shallow with a soft bottom, because there are lots of hippos defecting inside of it all the time? How do the pools compare to the river reaches up and downstream? Wouldn't you love to know what is happening at the bottom of a hippo pool? So would we! But it's hard to study a place you can't get into, and it's hard to get into a place inhabited by a number of 1,500 kg animals widely considered to be the most dangerous animal in Africa. 

We posed this problem to a group of robotics engineers from Carnegie Mellon University who have started an innovative company called Platypus. They design robotic boats that can autonomously create detailed spatiotemporal maps of water quality parameters. There are lots of uses for these boats, such as sampling in otherwise difficult-to-sample areas. Well, we have some difficult-to-sample areas! 

After lots of discussions, the folks from Platypus agreed to come to the Mara to spend two weeks with us in the field, using some of their robotic boats to map the insides and bottoms of hippo pools in the river. We warned them that some of their boats may not survive the trip, but they were up for the challenge! 

John and Chris from Platypus rigging up their robotic boat

To help the odds of boat survival, on the advice of a Maasai fellow, they decided to disguise the boat as a crocodile. They found this amazing foam croc head, which we attached to the front of the boat, and we covered the body of the boat with a camouflaged tarp. Other than the depth sensor and camera mounted on the back, it looked pretty convincing cruising through the water!

Robotic crocodile cruising the Mara

The first day they were here, we took the boats out for a test run on a stretch of river without any hippos. The boat looked great and worked well, but the real question is, will it survive encounters with hippos and crocodiles?

Deploying the boat for a test run

 I have to admit, I have no idea if this will work, and I'm both nervous and excited about it. If all their boats get eaten right away, this will be a long and awkward two weeks together. But if they work, we're going to discover some of the hidden secrets of the bottom of the Mara River, and gain invaluable knowledge about how hippos influence river ecosystems. Fingers crossed for the latter!