This is what it is like to be charged by a hippopotamus.

This is a post from the field on a National Geographic supported expedition to explore the Okavango River system from source to sand. 90 days, 1,000 miles, 3 countries, 2 rivers, 31 adventurers, 100% open data. Join us in real-time as we explore the beating heart of our planet.

You’re low to the water, in a flat-bottom canoe called a mekoro. Three metres away, a bow wave is moving toward the boat. It’s the only visible sign that an enormous bull hippo is running underwater, along the narrow river bed towards you. He’s bent on protecting the four females that make up his pod– three minutes ago, when your boat edged into this particular elbow of the river, he lifted his whole body of the water in a breach, a spectacular, unmissable warning. Just before he went under the water, he opened his massive jaws wide and roared, a sound that reminds you not just a little bit of Jurassic Park. You’ve entered his territory and he wants you out.

Photo by @shahselbe

This will end in one of two ways: the hippo will come up under the boat, jaws open, and will crush the thin fiberglass hull below you like paper. You and every piece of gear will be in the water, with an angry hippo and unknown number of Nile crocodiles and things will very likely end with a medivac. Or, this could be a very convincing bluff.

You’ve been on the river for thirteen straight days, sometimes drifting through dreamlike stands of emerald papyrus, sometimes pulling fully-laden boats through knee deep, leech-infested mud. The sweet smell of decomposing vegetation, of elephant dung and water lilies. It’s true that you started the expedition with a vaguely Disney-related fondness for the hippo, but things have changed. The stated purpose of your expedition is to assess biodiversity in the Delta. In reality this trip has been an exercise in hippo management.

Hippos are without a doubt the most dangerous animal in Africa, doubly so when you are on the water with them. A male can be twelve feet long and weigh more than three and a half tons — think of an angry minivan. The hippo has evolved to be perhaps the meanest grass-eater on the planet: their ferocity comes from a perfect combination of territoriality and teeth. Hippos use their gums to pull up the 88 pounds of grass they eat each night, so those teeth are there only to defend; against other hippos, and against anything else that might be stupid enough to encroach on their domain. You can recognize older hippos by the deep scarring on their backs from countless violent battles.

Hippopotamus amphibeus is often described in literature as mostly herbivorous. Mostly. This is the word that is ringing in your head as that wave approaches.

This is what it sounds like to be charged by a hippopotamus; or rather this is what my heartbeat sounded like when I was charged by a hippopotamus:

Heartrate data gathered during #Okavango14

In 2014, I and three other team members wore heart rate monitors, which collected biometric data every minute of every day on the river. This data, along with wildlife sightings, photographs, and GPS data were uploaded from the field in realtime and were available to anyone through a public API. The goal was to share as much as we could about the environment that we were in, as well as the human story of expedition life.

This year we’re publishing five heart rate streams, along with 14,000 habitat photographs, hi-res video and hundreds of field recordings. We also have a sensor-enabled Data Boat, which will take water & air quality measurements every five minutes along the entire length of the river system, giving us an unparalleled picture of one of the last nearly pristine wetlands on the planet.

This data is 100% open and is available for scientists and researchers, teachers and students, artists and the generally curious. Much of it will be uploaded within five minutes of it being recorded, and displayed on the map at Through this radical approach to sharing our experiences, we aim to bring as many of you into these extremely remote and tremendously important ecosystems.

Screen capture of the 2014 website, showing wildlife sightings, photos and GPS paths for four expedition team members.

Less than 200,000 hippos remain in Africa, clustered in a desperately small patches most of their former territory. There are hippos in South Africa, in Botswana, in Zambia, in Malawi, Zimbabe, Kenya, Uganda and Tanzania. They live in Namibia, Mozambique, Nigeria, Ethiopia and in the Congo. As I experienced in #Okavango14, the biggest populations on the continent are found in the Okavango Delta. But what about up North, where the river begins? What about Angola?

Hippopotamus distribution, historical (red) and current (green). Very little is known about populations in the interior of Angola.

We know that a small population of hippos live near the Southern border, but we don’t know if there are any in the upper reaches of the Cuito river, where the Okavango delta is born in the Angolan highlands. The civil war which raged across the country for nearly thirty years left much of the wildlife in this area decimated and hundreds of kilometres of terrain strewn with land mines. Have the hippos come back?

Next Thursday we’ll find out. We’ll launch our mekoros at the source of the Cuito River, and for the first two weeks of #Okavango15 we’ll explore one of the least studied wilderness areas on the planet. All of the wildlife sightings we’ll be making — hippos, elephants, birds, fish, reptiles, amphibians and plants — will add to our extraordinarily sparse understanding of the area.

This link lists all of the hippos that have been spotted so far:

Click that link right now, and you’ll see an empty map. But that will change as soon when we see our first hippo, as we edge our fragile boats carefully through its territory, and hope that it doesn’t charge.

Jer Thorp is an artist, writer and educator living in Brooklyn. He is the co-founder of The Office For Creative Research and a National Geographic Emerging Explorer.