Thursday, October 1, 2015

Huge wildebeest drowning in the Serengeti

Chris and I are currently back at Yale, but Geemi has been doing an outstanding job documenting wildebeest river crossings and drowning events this year in the Mara River. So far, there have been over 70 river crossings and just one drowning with 1,200 individuals. This is much fewer what we have documented over the past four years (an average of 5 drownings and ~7,000 individuals per year). All of our research thus far is on the Kenyan side of the border, but we just saw a report online of a huge wildebeest drowning that just happened on Sept. 29 in the Mara River on the Tanzanian side. From speaking with Mara Conservancy rangers, Geemi has learned the drowning happened fairly far downstream in the Serengeti, but we are still trying to find out more information. The original article was posted on Africa Geographic, and here's a photo from their story...

Wildebeest drowning in Mara River, Serengeti (photo from Africa Geographic)

Wednesday, August 12, 2015

ESA 2015

Amanda, Lily and I are at the Ecological Society of America meeting in Baltimore this year.  Amanda co-hosted a session called "Danse Macabre: The Role of Migrations and Mortality in Shaping our Planet" and presented on the "Causes and consequences of wildebeest mass drownings in the Mara River, Kenya".

I gave a poster on "Tracking flood pulses and their impacts on water quality using a low-cost, open-source monitoring network in East Africa."  Data from the network is available on Thingspeak.  If you're interested in the base code that I use in the water level stations and the weather stations (take a measurement and then upload to Thingspeak via a GPRS connection), you can get it here -

Saturday, April 25, 2015

Geemi in Action

Some photos of Geemi documenting hippo aggregation numbers during extremely low flows (Thanks to Angela @ The Mara Conservancy for the photos!).

Friday, March 20, 2015

Non-seasonal wildebeest crossings and cholera outbreaks

A herd of zebra and wildebeest just crossed the Mara River, North of Serena.  Geemi got a few good pictures of it.  Here is one of them...

The Mara is amazing low right now.  We estimate the flows at around 1 m3/s at Purungat Bridge (see here for the water level data).  The zebra and wildebeest had no trouble crossing the river.

Unfortunately, the low flows are probably contributing to the cholera outbreak in the upper catchment.  Read more here - Bomet hotels closed over cholera outbreak and here - Two die of Cholera in Bomet.  

Thursday, March 20, 2014


So here's how Tuesday unfolded...

2:50 pm - Alternator bearing froze in the middle of the Mara. We had already been suspicious of the new sound coming from our engine, and a friend's mechanic had checked it out, diagnosed the problem, and determined we could safely drive the 2 hours to the nearest town. We broke down a few hundred meters later.

2:53 pm - We had already ordered a new bearing from Nairobi as soon as we heard the diagnosis. Determined we couldn't get the part from Nairobi until the next day. Called our mechanic in Narok, 2 hours away, to source a more local alternative.

3:07 pm - Called our field assistant in Mulot, 1 hour away, to look for a back-up option.

3:11 pm - Called our friend whose family owns a shop in Aitong, 30 minutes away, to look for a back-up, back-up option. The closer the towns, the smaller they were, and the less likely we could find the part we needed, but it was worth the try.

3:49 pm - Determined a used alternator from Narok was the best/only option. Sent all the money we could (not enough) via cell phone to our mechanic to purchase the alternator.

4:05 pm - Our mechanic left Narok on a motorbike with the used alternator, heading for the Mara. The roboticists and I went to hang out with our friends we had been visiting. Chris, like a true sea captain, wouldn't leave the vessel, and insisted on sitting outside the gates in the afternoon sun with the Land Rover.

6:49 pm - Our mechanic arrived at our Land Rover in the Mara. She (the Land Rover) and Chris are outside the gate, and it's starting to get dark.

7:30 pm - Chris rolled into our friend's place, new (used) alternator in place and the Land Rover purring like her normal self again. Decided it was too late to drive, and a great opportunity to spend more time catching up with friends, so set up our tents for the night.

4 hours and 40 minutes from breakdown to repair in the middle of the Mara-- not bad! Of course, we have some great friends to thank for their help in getting things running again so quickly, and having a comfortable place to camp for the night. In Kenya, logistics are all about who you know, and how easily you can contact them. I can't imagine having worked here before cell phones!

Tuesday, March 18, 2014

True safari experience

Wouldn't be a true safari experience without a breakdown! Alternator bearing froze approximately 500 meters after a mechanic told us we could make the 2 hour drive to town. Fortunately we're near some friends who can help out, and we're pulling out all our logistics tricks to sort this out... wonder where we'll end up tonight...

Wednesday, March 12, 2014

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!

Saturday, March 8, 2014

Closing the streams

After about a month of running our experimental streams, it was time to finish out the experiment. The main thing we wanted to measure was how much biofilm and of what different types grew in the streams under different treatments. Biofilms are groups of microorganisms which grow on a surface. We usually think of biofilms as being comprised of algae, but they can also have a lot of bacteria in them as well.

I have to admit, I was a little worried nothing would grow, which would make it difficult to measure any effects of the treatments. Fortunately, that was an unnecessary fear! After 4 weeks of running, it was incredible how much biofilm our streams had grown! You could clearly see it on both the tiles and gravel we had placed in all the streams.

Biofilm growth in tiles in the streams 
Biofilm growth on rocks in the streams
 A lot of the biofilms were green and looked like algae, like this rock below, but we took measurements that will help us determine the quantity and composition of the biofilms in each stream.

A rock covered with algae
 We will have to analyze all our samples and run statistical tests on the data before we will know if the experiment "worked" scientifically speaking-- that is, did the treatments have significantly different effects on biofilm development that we could measure? However, after running smoothly for one month and growing lots of great biofilms, I can happily say the experiment was a success! When we started this process, we didn't even know if we could get these things to hold water, much less act like small streams. Truly, we owe all the success of this experiment to Paul Geemi, our tireless field assistant.

Geemi changing water in the streams
Geemi camped next to the streams for one and half months, just to help maintain them and keep them running. He changed out 50% of the water in each stream every day-- that's a lot of pumping water and filling and carrying buckets! He monitored the power that kept the paddlewheels turning and switched things over to battery when there were power outages, even in the middle of the night. He also did a great job doing outreach and education for the many people who came by and wanted to learn about the experiment. And through it all, he kept the most thorough and well-written field notes I have ever seen!

Geemi doing outreach about the streams
Field biology is full of unsung heroes-- the people actually out there in the heat and the rain and the dark, doing the work, carrying the heavy weight, monitoring the results, keeping things working. Often times, these are not the same people who end up analyzing and writing up the data, so they don't always get a lot of credit for the work they do. Geemi is definitely the reason these streams worked as well as they did (or even at all!), and we are super grateful to be able to work with him. Thanks Geemi!

Geemi, the unsung hero of the experimental streams

It all comes back to silica

After Emma and David left, we hosted two colleagues from Antwerp University, Belgium, in the Mara. Jonas Schoelynck and Eric Struyf study silica cycling and are particularly interested in the role animals might play in the silica cycle. 

What is silica? It's commonly found in nature as quartz, but it can also be found in living organisms like grass (it gives grass the sharpness that can cut you). Silica is taken up by diatoms in the ocean, that are at the base of the food web, and it is often limiting to their growth. That it, the more silica there is, the more diatoms there are, and the more overall productivity in that region of the ocean. A lot of the silica in the ocean is brought in by rivers, and it has generally been assumed that all of that silica originated from weathering of rocks. But recent advances in the last decade have shown that animals can actually contribute a great deal of silica by eating grass and defecating it out, and the silica defecated by animals is more reactive than that simply eroded form rocks. If it involves animals eating and defecating grass, we have the perfect animal to study...

Hippos basking in the Mara River

Jonas and Eric came to the Mara to work with us to investigate the role hippos might be playing in the silica cycle. To study this, they collected water and sediment samples from multiple reaches of the river with varying densities of hippos.

Eric collecting a pore water sample from the Mara

Jonas and Eric collecting a sediment core from the riverbank
We did this throughout a 100 km reach of the Mara, which was a great opportunity to see some beautiful places, and to learn a lot about silica.

Jonas and Eric on the banks of the Mara

They also took sediment samples in the middle of the grasslands for comparison.

Jonas and Eric collecting a sediment core in the savanna
These guys are super passionate about their subject and a lot of fun to work with, and after a week in the field together, they pretty much convinced me that everything comes back to silica cycling! Best of all, they took a system and an animal about which we have thought a lot, and introduced a whole new component to think about that we hadn't considered before. It will be really exciting to see what these new analyses can teach us about the Mara.