| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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A Letter from the field Into the Heart of Uganda's Impenetrable ForestThe steep, dense slopes of Uganda's Impenetrable Forest occasionally echo with the screams of chimpanzees or the hollow staccato popping of a gorilla beating its chest, but it is the sound of raindrops on leaves, footsteps in deep, scrunchy loam, and the calls of unseen canopy birds that I most associate with the place. Last September, herpetologists Alan Channing, Jens Vindum, and I were standing in profound darkness, dressed in clinging, muddy T-shirts, the cold rain pouring down our backs, searching with our flashlights to locate the source of a new sound. Loud, clear, repetitive triplets of chirping seemed to be coming from a tiny hole in the bank of the road cut--right in front of us. After a full ten minutes of triangulation, lights off to listen, then on again, and accompanied cursing, Channing spotted a tiny earth-colored frog sitting on a batch of perfect white eggs. Within 30 seconds we found another--a male sitting not 20 centimeters from the first. We knew this genus, Schoutedenella, from earlier expeditions to Zambia and Tanzania. It is a curious group of small terrestrial frogs, whose tiny males have fingers nearly as long as their bodies. This was a new species for the Impenetrable Forest list; one we had failed to find during our first amphibian survey here in 1990. I would love to believe that it is the Uganda government's intense interest in reptiles, amphibians, and other small vertebrates that has led to our four months of fieldwork there since 1990, but such is not the case. It was the desperate need for hard currency required to rebuild this East African nation following nearly two decades of terror and misrule by former presidents Idi Amin, Milton Obote, and others. A major source of hard currency in this part of the world is tourism, and tourism can be spelled: g-o-r-i-l-l-a. Thanks largely to an extremely effective, but misleading, international conservation fund-raising campaign, it became widely accepted that the world's last populations of mountain gorillas are found only on the higher slopes of the Virungas, a chain of volcanoes bisected by the borders of Rwanda, Zaire, and Uganda. In fact, fully half of the world's six hundred or so mountain gorillas inhabit Uganda's Impenetrable Forest, now known as Bwindi Impenetrable National Park, about 40 kilometers to the north. It was the inevitable advent of tourism that had led to our first invitation to the forest by Tom Butynski and Jan Kalina, the husband-and-wife team who had been studying the forest and its mountain gorilla populations since the early 1980s. Because Tom and Jan were concerned that heavy tourism might negatively affect the forest, they were anxious to document the species in its various ecosystems. This was a remarkable opportunity. With the exception of a book on snakes by C. R. S. Pitman, a game warden during the colonial period, virtually no herpetological work had ever been published on Uganda, much less the Impenetrable Forest. Ours was the first amphibian survey ever undertaken in the country, and our report was an illustrated account of the 28 species we found, four of which were previously unknown in Uganda. The initial report included ecological recommendations, but it was also crafted to serve as a rough field guide for the forest rangers. Although a more formal, scientific version has since been published in the Journal of African Zoology, so scarce is information of this kind that color photocopies in our original report are still being used to identify frogs from distant, inappropriate areas all over Uganda.
Last Spring, I received a letter from Simon Jennings, director of the Institute for Tropical Forest Conservation, at Ruhizha, inviting us back, this time to do a reptile survey. Recognizing this as an opportunity to also clear up some leftover amphibian questions, we accepted. Since 1990, the social instability in the Virunga area of Rwanda has made Bwindi the world's premier gorilla-watching destination. It earns more tourist dollars than all other Uganda national parks combined. After interminable negotiations with the new Uganda Wildlife Authority, I was able to broaden the scope of the expedition to include surveys of freshwater fish and terrestrial arthropods. Vindum and I were joined at various times by others including Charles Griswold, the Academy's spider expert, Channing, an authority on bioacoustics from South Africa, and James Vonesh, a young ecology graduate student from the University of Florida. Hollywood interpretations notwithstanding, the African bush is not "crawling" with snakes. Like most predatory species, they are not particularly numerous anywhere; in fact, for every snake we caught in Bwindi, we could have collected hundreds of frogs, beetles, or virtually anything else. After countless hours spent trekking up and down the Buhoma Road, two kilometers each way, looking for sunning serpents by day and nocturnal hunters by night, we only found eight snakes, although these did include a possible new subspecies of green tree snake (Dipsadoboa), an outrageously colorful red-and-black striped snake (Bothropthalmus) and an extremely venomous rhinoceros viper (Bitis nasicornis). One morning, our tireless, mirthful Bakigga field assistants, Godfrey Mayooba and Narcensio Owoyesigire (known to us respectively as "Mr. G" and the "Donut King," because of the caps they wore) brought in two newly hatched bush snakes along with news of others emerging from a hole in the ground. We were busy preserving specimens from the night before and did not return with them. But soon sounds of excited voices from the road below got our attention. It seems that the hole was one of several entrances to a large nest of biting, stinging ants, identified later as Myrmecaria natalensis. By the time we reached the scene, Owoyesigre was busily digging out the nest with a large hoe. With each stroke, either a bunch of snake eggs or a baby snake was unearthed. By the time he reached the bottom of the nest--at the level of the ant eggs--we had found a total of 540 snake eggs. Based on their shape and later identification of the newly hatched babies, we have determined that the eggs belonged to four different snake genera. While reptile eggs, and for that matter reptiles themselves, are frequently found in termite mounds, an association with predatory, biting, and stinging ants is quite surprising. Clearly, gravid female snakes selectively make their way into these ant mounds and lay their eggs at the bottom, presumably unmolested by the ants. I have no idea whether the ants derive any benefit from the snake egg clutches, but at these elevations--in this case 2,356 meters--the bottom of the nest must afford a more stable temperature for the eggs than the surface. Mayooba told us that the local farmers frequently turn up baby snakes and eggs while tilling their hillside fields. Alan Channing, with his sophisticated sound equipment, added a dimension to this trip that we lacked in 1990. We were able to record frog voices and to associate them with a particular species. Like birds, frog calls are very species-specific. Knowing a call not only allows the investigator to identify a species without actually seeing the frog, but the calls can also be used in phylogenetic analyses. Many of the Bwindi species have never been recorded on tape. One night, we were ankle-deep in a small swamp when we heard a lovely, soft trilling sound. Although Channing insisted it was an orthopteran, perhaps a cricket, and stomped off after ten minutes, something made me stay. I finally spotted an exquisite golden leaf-folding frog, Afrixalus laevis, creeping slowly along the top of a large, broad leaf. Although I watched it for another 20 minutes, the frog remained silent. I was fully vindicated the following night when Channing heard the call again, recorded it, and actually captured the Afrixalus that had made it. So far as I know, this call has never before been described or sonogrammed, even though the species is widespread, found from the rainforests of Liberia east to Bwindi. In 1967, a Danish colleague, Arne Schiotz, described a new subspecies from the extreme western part of this range, in the Ivory Coast and Ghana, which he named A. l. vibekensis, after his wife, Vibeke. In his description, he characterized the call of A. l. vibekensis as a "high- pitched buzzing, of low intensity." The sound is entirely different from the lovely, flute-like trilling we heard and recorded at Bwindi. This means that, given the species- specific nature of frog calls, the subspecies Schiotz described 30 years ago is most probably a full species, Afrixalus vibekensis.
Although sightings of such rarities as l'Hoest's monkey were reasonably frequent during our combined four months there, Jens Vindum was the only one of us to actually encounter mountain gorillas in Bwindi. Our transect, the Buhoma Road, originated quite close to the new tourist operations at Buhoma. The path is beset on either side by steep, densely-vegetated slopes, and one morning as Vindum was trudging south, he heard rustling some 50 feet ahead. A hairy black face suddenly appeared from the ferns, carefully peering up and down the trail. Then a half-grown gorilla scuttled across the road and into the bushes. A moment later, the entire group followed, 13 animals in all, including a silverback male. Once across the road, the gorillas stopped to feed, explore, and generally fool around; a number of them climbed trees just yards from the road. Vindum leaned back on his snake stick and watched in fascination. After a full five minutes of undisturbed (and free) gorilla watching, another noise began to emanate from the bushes. With muffled oaths and the unmistakable twang of American accents, a sweating, filthy, exhausted group of ten tourists and their African guide stumbled out onto the road. They had been tracking the gorillas for hours, since before dawn, up and down muddy slopes, through patches of nettles and thorns, wading through muddy streams. As soon as the group spotted the gorillas, they fell into a rapturous silence, and stared transfixed at the animals in the bushes in front of them. All of their suffering had been worth it, the sums of money well-spent! After a few moments, the tourists became aware of Vindum, standing quietly nearby. As their jaws dropped in surprise at simultaneously seeing a human and realizing where they had ended up, Vindum remarked, in a slow drawl: "You should'a taken the road." When the material we brought back in November is finally analyzed and our findings published, the Bwindi Impenetrable National Park will be the only forest in Uganda whose vertebrate fauna will be nearly fully documented. This comes none too soon, for the only wildlife attractions left in Uganda are her forests. The picturesque settings of Murchison Falls and Queen Elizabeth National Parks still remain, but the incredible concentrations of big game are largely gone, shot to supply food for rebel groups or devastated by successive waves of refugees from tragic, incessant warfare in neighboring states. At lunch in Kampala just before we left, Jim Else, the European Community Advisor to Uganda's Ministry of Tourism, Wildlife, and Antiquities and an old friend, told me of an aerial survey that had been commissioned to seek out any game animals that might still remain isolated in Uganda's remote northern areas. They hoped that such remnant populations might serve as source pools from which Uganda's national parks might be repopulated. "What they found," he said, "was absolutely nothing." The overall fragility of Africa in general, and this part of Africa in particular, has become extremely poignant to me since our Impenetrable Forest trips. During our stay in the forest in 1990, Tutsi refugees who had fled Rwanda in the 1950s--soon after a bloody conflict with their archenemies, the Hutus--and had been living in Uganda for a generation, re-invaded Rwanda in force. Although we were unaware of it at the time, fighting had been going on at the border, less that 30 kilometers from us. This fighting eventually led to the appalling genocide that took place in Rwanda in 1994. Last November, as we were leaving Bwindi, there were armed militia in the town of Kabale. Meanwhile, Botugota, a small village we had passed through two weeks earlier, had been swamped with more than 10,000 refugees from the fighting in Eastern Zaire. Robert C. Drewes is a Curator of Herpetology at the California Academy of Sciences. |
summer 1997
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