Savannah trapped in the forest
Two weeks ago the west bonobos crossed the Badzungu River entering the forest of the neighbouring village. Since the beginning of April there is an agreement with this village so we can follow the bonobos when they cross. Often it is hard to follow the group as they rush through the swampy forest along both sides of this river. During the crossing, the morning team lost the group, so that day we went out to search for bonobos on the west side of the Badzungu. We went further westward and came across a small savannah where the bonobos had been seen a couple of days before. Working in a dense forest makes you learn to appreciate an open space like this, about five hundred meters long, enclosed by forest. The moment became even more memorable when we heard bonobos from three directions as we entered the savannah. We found one of these subgroups fifteen minutes later and followed them as they walked along the forest edge. We were hoping to see the bonobos cross the open space, walking bipedally while carrying fruits, to meet up with the other group. This is the typical views of how the transition from forest to savannah happened in our early ancestors. Of course this didn’t happen (although at one point, a male was three meter in the savannah, eating Afromomum, a big herb of the ginger family) and the group travelled back east.
Last week, Niina and I went on a bird trip to lyaka, a temporary hunting camp north of the Lokoro River. The camp fisherman brought us over in a pirogue and from there it took us a bit more than an hour to get to Iyaka. A couple of hunters were staying in one of the huts and they showed us a roof where we could put our tent under. They were surprised and I felt proud that I was able to communicate with them in Lingala. Iyaka is surrounded by several extensive savannah patches that are regularly burnt to promote regrowth of grasses. We stayed for one night and made several tours in the savannah to see typical birds. Blue-breasted bee-eaters (Merops variegatus) were perched on almost every small shrub, taking off to eat flying insects now and then, and palmnut vultures (Gypohierax angolensis) were souring overhead. We saw a long-crested eagle (Lophaetus occipitalis) resting on a termite mound and in camp we had yellow-billed kites (Milvus aegyptius), fawny-breasted waxbill (Estrilda paludicola) and African grey parrots (Psittacus erithacus) as visitors. Apart from that, the ornithological value of our trip was a bit disappointing, but we enjoyed the change of habitat and surrounding.
On the first day, just before sunset, we saw a female sitatunga (Tragelaphus spekei). Sitatungas occur throughout the rain forest belt of Central Africa, but are mainly found in swampy areas and forest clearings. Forest buffaloes (Syncerus nanus) and bongos (Tragelaphus euryceros) are other species that are adapted to the open areas within the tropical rain forest. The idea is actually that these species got ‘trapped’ when the forest expanded. You should know that most of the Central African rain forest is relatively young forest. The glacial periods within the last million years have had an important impact on the distribution of forest in Central Africa. During a glacial maximum, the global climate was generally cooler and dryer, resulting in the contraction of the forest. The Congo basin was covered by extensive savannah habitat until relatively recently. In certain areas, as around Iyaka, patches of savannah still exist, although they are now maintained by people using fire. In some of these places, hundreds of kilometers away from the continuous grasslands of eastern and southern Africa, lions could be found until a couple of decades ago. The Bolobo region between the Kwa and Congo Rivers is a mosaic of forest and savannah. Last year I spent six weeks in this region and the local people I interviewed knew bushbucks, servals, side-striped jackals and even spotted hyenas (although these had not been seen for years). All of them are typical savannah species. Occasionally, a group of lions visit this region as well. Most of this is not well documented in the literature. It shows how little the scientific community knows about the basic ecology of large-bodied species in the Congo basin.