Crocodile City


 

Crocodile City

 

2 August 2013:  Watsi Kengo, Salonga River, DR Congo.  Yesterday we returned from Lotulu, a ranger outpost on the Yenge River, which took us about 7 hours to reach from Watsi Kengo.  After heading a couple hours east along the Salonga River from Watsi Kengo, a small branch (the Yenge) diverted to the southeast, and as we descended the river, just inside the western boundary of Salonga National Park, I noticed a subtle change in scenery.  The river was much smaller, only about 50 feet wide in some places, and innumerable trees had fallen into the river, creating a challenge for our captain to navigate around them.   We had seen fallen trees on the Salonga too, but it was easy to go around them because they were close to the riverbank.  But on the Yenge, there wasn’t much room to maneuver, so we had to move slowly and carefully to avoid colliding with trees hidden just under the surface of the water.  More than once we felt jarring vibrations as the bottom of our boat scraped across logs under the surface of the water.  Below is a photo of the landscape on the Yenge River.

We saw a few lightning-quick monitor lizards (Varanus) basking on logs in the river, but I was disappointed that we didn’t see any trace of crocodiles—I had heard so much about them and was puzzled by their failure to appear.

 

Salonga is famous for the slender-snouted crocodile (Mecistops cataphractus), which has an unusually long and narrow snout compared to most of the other 25 species of crocodiles known from the world.  Like all the other crocodiles in Africa, they are considered to be an endangered species for numerous reasons, including over exploitation from hunting and habitat loss.  They occur across most of the remote, forested regions of Central Africa in lakes and rivers.  The second species that might occur in Salonga is the Nile Crocodile, which is one of the larger species of crocodile known from the world.  Until recently, it was thought that there was only one very widespread species in Africa (Crocodylus niloticus), but a recent study that examined their genetics split them into two species.  Thousands of years ago, the Sahara Desert was a much wetter place, and crocodiles were much more common and widespread than they are now.  The ancient Egyptians occasionally mummified animals, and it turns out that one of the crocodiles they immortalized provided some DNA that helped scientists from the recent study identify the two species of Nile Crocodile.  Nowadays, only one species seems to occur on the Nile River, and a few populations have become isolated in oases in the Sahara as it became increasingly arid over the last several millennia.  According to a map of genetic samples used in the study, Nile Crocodiles from the area around Salonga probably belong to Crocodylus suchus, the recently recognized species.  I wondered which species of crocodile would occur in the area I was entering, but I would have to wait several days for the answer.

 

As explained in my post below, we set up a camera trap to see what mammals might be active in the area, and we used drift fences with pitfall traps to help us survey the amphibians and reptiles of the forest.  Although we found at least three species of Hyperolius treefrogs we hadn’t seen before, most of the animals we trapped or found were the same species we had already collected at Watsi Kengo.  This is good and bad news.  The bad news is that we spent a large amount of time and money with very little payoff to get to Salonga.  The camera trap took some blurry footage of insects as they crawled across the lens, triggering the camera to record, but nothing else showed up.  The good news is that we can use the very large and diverse list of species we found at Watsi Kengo (some of which are extremely rare) to extrapolate what is likely to occur in Salonga, which will help with future conservation planning, and for general knowledge about the park’s fauna.  Some of the toads and Leptopelis treefrogs that we found at Watsi Kengo and Salonga seem to be new species, and that is good news too—we can now document that at least some of these new species are protected by the park. 

 

Perhaps our luck would have changed if we had been able to stay longer, but the slim pickings for animals and miserable conditions at Lotulu encouraged us to leave after the better part of a week.  In addition to the ever-present mosquitoes, Lotulu was unusually endowed with biting and stinging insects, including potentially disease-ridden tsetse flies, small black flies, and a sizable population of bees.  The bees showed up every morning just after dawn, and swarmed over anything with interesting colors or smells, including us.  Although one intrepid bee somehow found its way inside my pants, I avoided being stung, but the incessant buzzing and fear of being stung created very difficult working conditions.  Other members of the team were not so fortunate.  Aristote, who was stung twice, said the sting was unusually painful and lingering.  Our poor cook du Gaul was stung multiple times on the face and neck as he tried to cook our meals every day.  It was difficult for me to understand how the park rangers at Lotulu could stand to live there for a year at a time, but I imagine eventually one just gets used to it.

 

After a couple of days at Lotulu, I began to understand why we hadn’t seen any crocodiles in the late afternoon when we had arrived.  The crocs are most active at night, as evidenced by the presence of a sizeable individual who showed up at the river at our camp every evening without fail.  Although I was pretty sure it was a fish-eating Mecistops crocodile, I couldn’t see it well enough to exclude the possibility of it being a Nile Crocodile, which are infamous for preying on people at the edge of rivers. At such places they are especially good at ambushing, capturing, and dragging their prey into the water, where they can be eaten at leisure.  Because most of the interesting treefrogs were in reeds close to the river, one of us watched the frogs while the others stood guard to warn everybody else if a crocodile came too close. 

 

On my last night at Lotulu I joined the rangers in a dugout canoe to look for crocodiles with spotlights.  We let the boat float downriver with the current, and as we moved through the prehistoric landscape, I heard many interesting calls and shrieks from unknown animals in the forest.  Confused by our lights, fish jumped out of the water, and even into our boat.  Aristote’s skimask couldn’t protect his eyes (or mine) from moths that flew into our faces, attracted by the unfamiliar glow of our headlamps.  Here and there, I could see the distinctive orange eyeshine of a crocodile, but they slipped underwater before we could get a really good look at them.  Our jaunt down the river was cut short after less than an hour when a thunderstorm rolled in and soaked all of us as we returned to the camp.

 

When we finally left Lotulu, I was relieved to be leaving the bees behind, which disappeared shortly after our boat pulled away from the shore, but I was a bit sad to be leaving the most pristine forest I had ever seen.  As the morning sun slowly burned away the previous evening’s mist, we motored back towards Watsi Kengo, but the Yenge had one more surprise in store for us.  Because the crocodiles are cold-blooded, with body temperatures identical to their surroundings, they become uncomfortably cold at night as the temperature drops.  To warm themselves up in the morning, they drag themselves onto a fallen tree in the water, or a sandbank to bask in the sun.  I would have been thrilled to see only one crocodile, but every few minutes we observed a crocodile caught off guard by our approaching boat.  Immediately after seeing us, they dove into the water, often after a running jump from the steep, sandy slopes of the riverbank.  This was the pristine Congo of my dreams, and I feel extremely lucky to have experienced it.  The future of the crocodile in Africa is uncertain at best, but at least at Salonga, we did not encounter any poachers, and the crocodile population seems to be very healthy, with a wide range of juveniles to adults.  Below is a photo of a young crocodile.

We plan on leaving Watsi Kengo tomorrow to begin our slow westward return to Mbandaka over a week or so.  Although we continue to find some very interesting things, including a small Jameson’s mamba that briefly escaped on our boat yesterday, I am eager to get the collection back to the lab where I will be able to have a more complete understanding of the animals’ evolution and relationships.  That and I’m getting tired of the bugs!  I hope my next blog post will be from Kinshasa in about 10 days as I wrap up paperwork and prepare for the flight home.  I should be able to updated non-illustrated posts with some photos, including some interesting stuff for the cybertaxonomy project for my students.

 

Quick final note for this post:  I noticed on the last brief check of my email that I am getting requests from people to register on the blog’s website.  I think it’s great that so many people are interested and following the blog, but I set things up so that only my graduate students can post on it for the cybertaxonomy project.  With my limited satellite access, I wouldn’t be able to respond to multiple comments from the general public, so hope everyone understands.  Thank you!

 

 

 

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