Recent surveys carried out in Cameroon in the Mbam Djerem National Park, in Gabon in the Bateke Plateau National Park, and the adjoining Bateke Plateau area in Congo, have recorded the presence of de Brazza's monkey (Cercopithecus neglectus) on both sides of the Djerem River in Cameroon, along the Mpassa and its tributaries in Gabon, along the Nambouli River in the Lefini Reserve in Congo, and up to the right bank of the Ogooué River on the Congo side of the border. These areas lie at the northern and southern edges of the Central African forest block, where rivers have relatively wide bands of riparian forest. As for the range extension of the talapoin (this volume), the species may simply have been overlooked by previous rapid wildlife surveys. It has an antipredator behavior that renders it relatively inconspicuous, tends to live in small family groups in the region, and lives in habitats that are difficult to survey on foot. However, unlike talapoin, it calls every morning along major watercourses, and can be heard for some distance. It is possible that the southern limit of this species in Gabon may be the Ogooué River. Future survey teams are encouraged to familiarize themselves with the long call of this species and to be aware that it can occur in gallery forests throughout the savannas of the Bateke Plateau and also in the area between the Mbam, the Djerem, and the Lom in Cameroon.
De Brazza's monkey (Cercopithecus neglectus) is widely distributed in Central Africa, from the Atlantic coast of southern Cameroon, through Equatorial Guinea down to northern Gabon, and then eastward through the forest block and some of the fringing transitional forests to the Ruwenzoris (Kingdon 1997; IEA 1998). In West Central Africa it has been assumed that their distribution is limited to the north, as it is in many other species, by the Sanaga River. The southern limit is less clear. It was earlier thought that the species did not occur south of the Ivindo watershed (Malbrant and Maclatchy 1949) but later maps show them to half way between the Ivindo and the Ogooué (Kingdon 1997; IEA 1998). The published maps (Kingdon 1997; IEA 1998) suggest that they are absent from the Bateke Plateau and from the “Lake region” between the Komo and the Ogooué rivers (Fig. 1).
The Mbam et Djerem National Park was created in 2000 in central Cameroon. It lies across the Guinea-Congolia/Sudania regional transition zone (White 1983) between the main forest block and the Guinean savannas to the north (Fig. 1). The Djerem River, which is, in fact, the upper reaches of the Sanaga, runs north-south through this park, and is lined by a broad band of riparian forest. The southeastern part of the park is lowland, tropical, semideciduous forest; the northwestern part is wooded and bush savannah with gallery forests lining the watercourses. The transition between the forest and the savannah has a relatively high biodiversity because of the interlacing of the two main habitats. The forest has been slowly creeping north since the 1950s (evidenced by the old maps of the region and present conditions, which show the contrast between savannah in the past and young colonizing woodland today).
Another new national park, Bateke Plateau, was created in 2002, in southeastern Gabon. The vegetation is structurally similar to that of Mbam et Djerem: The main forest block of Gabon is at the extreme northwest of the park and there is a progression through forest-savannah mosaics to bush savannah and some extensive areas of grass savannah toward the east, at the Gabon-Republic of Congo international border. The Bateke Plateau in general is a savannah and gallery forest mosaic that extends far to the east, across the Republic of Congo, into western Democratic Republic of Congo. The Lefini Reserve is also in the Bateke Plateau, a little farther south than the Gabonese Bateke National Park (Fig. 1) and has the same vegetation: a mosaic of galley forests and savannas. The Bateke Plateau National Park in Gabon is bisected northsouth by the Mpassa River, which like the Djerem in Cameroon, runs through a wide corridor of riparian forest.
A series of wildlife and vegetation surveys were carried out in all three protected areas (Mbam et Djerem, Cameroon; Bateke National Park, Gabon; and the Lefini Reserve, Congo) between 2000–2005, partly as reconnaissance missions but mostly to provide the baseline for the park monitoring of wildlife and human impact. In addition, in the Congolese part of the Bateke Plateau just across the border from Gabon, a wildlife and socioeconomic survey was carried out in 2004 to evaluate the potential for an additional protected area that could form a transboundary park in the future.
De Brazza's monkeys were recorded nine times along the Djerem River and three times on various tributaries in Mbam et Djerem. In the Bateke Plateau (Gabon) it was recorded at least a dozen times: in the riparian forest along the Mpassa River and on eight different tributaries. In the Bateke Plateau (Congo) it was seen along two of the upper tributaries of the Congo (just across the frontier, south of the village of Edjangoulou: Fig. 1), several times on the Ogooué River, and twice in the Lefini Reserve along the Nambouli River.
We also asked local hunters about the monkey species present in the areas. In Mbam et Djerem de Brazza's monkeys are well known by their (onomatopoeic) local name, founga, in Gbaya (very similar to the Mboko name pounga from Odzala in Congo [F. Maisels pers. obs.] and to the Bakota name, pounnga, in Gabon [Malbrant and Maclatchy 1949]). By contrast, the Bateke hunters in Gabon ascribed the characteristic long call of the species to Cercopithecus cephus. However, one Gabonese hunter knew the species and its calls, and noted that it was found also at Edjangoulou, about 60 km farther north on the plateau, corroborating the observations on the Congo side (Fig. 1). The Gabonese Teké name is mfoue; the Congolese Teké name is nfua.
These records show that de Brazza's monkey occurs about 100 km farther north in Cameroon, about 140 km farther south in Gabon, and about 80 km farther west in Congo than was previously known. However to the east (Central African Republic and Republic of Congo), it occurs (or occurred) much farther north and south, respectively, so it is likely that this species was simply missed during surveys in the past. Downer (1998) carried out a wildlife survey and also questioned hunters in the Lefini Reserve in 1996 in Republic of Congo. Although the species was not recorded during the survey, the hunters said that de Brazza's monkeys occurred there, which was confirmed during the 2005 survey. The Bateke Plateau is heavily hunted (especially on the Congo side) so monkeys in the area will be very wary and in probably much reduced in numbers.
De Brazza's monkey is considerably more inconspicuous than most other guenons. It generally avoids living in polyspecific troops, and at least in Gabon, northern Congo, the Bateke Plateau and central Cameroon, lives in small family parties (Gautier-Hion 1988; N. Bout, C. Inkamba-Nkulu and F. Maisels pers. obs.). In areas where they are hunted, they freeze, being motionless sometimes for hours when disturbed, and hide their otherwise highly visible white beard and buttocks by crouching (Gautier-Hion and Gautier 1978). Like the talapoins, Miopithecus, and Alien's swamp monkey, Allenopithecus nigroviridis, their habitat is inundated forest along watercourses, which makes them less likely than terrestrial species to be seen by survey teams walking through forests and savannas. In fact, they are most often detected by their calls in the early morning, or from a canoe while traveling along rivers. To people unfamiliar with their vocalizations, the “boom” could be confused with that of Mona superspecies (C. mona in the northwest and C. pogonias in most other places west of the Congo River [Lernould 1988; Kingdon 1997; IEA 1998]). Recordings of C. neglectus calls can be found on the CD of primate vocalizations in Gautier-Hion et al. (1999), and it is important to note that (1) the two booms are longer than those of C. mona; (2) they are separated by a soft, audible sub-boom caused by the re-inflation of the vocal sac, and (3) that the “cough” following the booms is a series of single notes, unlike the rapid double cough of C. mona.
Although de Brazza's monkeys are not listed as threatened by the IUCN, they are nevertheless listed in Appendix II of CITES (Inskipp and Gillett 2005). At least in parts of the Bateke Plateau, it is clear that they are uncommon and very wary of humans; despite their antipredator behavior they are vulnerable to hunters if they are detected. We urge wildlife survey teams to be aware that de Brazza's monkeys may be present along rivers in the savannas of the region, and to familiarize themselves with the vocalizations of this rather secretive species. In Gabon, the species almost certainly occurs up to the right bank of the Ogooué River in the Bateke Plateau area, and perhaps also in the very marshy lake region between the Komo and the Ogooué to the west of the country. Unless it has been hunted out, in Congo it is almost certainly present along watercourses across the whole of the Bateke Plateau between the Congo River and the Ogooué,. In Cameroon, attention should be paid to the possibility of this species occurring along the major watercourses to the east and west of the Djerem: the Mbam and the Lorn (Fig. 1).
We thank the Governments of Cameroon (MINFOF), Gabon (CNPN and the DFC) and Republic of Congo (DFAP) for their efforts in wildlife conservation. For funding, we are grateful to the following: USAID (Congo Basin Forest Project); FEDEC (Foundation for Environment and Development in Cameroon); the British High Commission, Yaoundé: Global Opportunities Funds; the John Aspinall Foundation; WCS New York; WCS Cameroon; WCS Gabon; and WCS Congo. Thanks to all the staff of the projects at Mbam et Djerem, Bateke Plateau (both Gabon and Congo), Lefini, the JAF—Mpassa project, WCS Cameroon, WCS Congo, and WCS Gabon. Finally, enormous thanks to the trackers and porters from all sites.
 Authors ' addresses:
Fiona Maisels, Wildlife Conservation Society, 2300 Southern Boulevard, Bronx, New York, NY 10460–1099, USA. E-mail: <firstname.lastname@example.org>.
Nicolas Bout, WCS Gabon, BP 7847, Libreville, Gabon and John Aspinall Foundation, John Aspinall Foundation, BP 583, Franceville, Gabon.
Clement Inkamba-Inkulu, presently at University of East Anglia, Norwich NR4 7TJ, UK.
Liz Pearson and Paul Aczel, John Aspinall Foundation, BP 583, Franceville, Gabon.
Rufin Ambahe, Edgar Ambassa and Roger Fotso, Wildlife Conservation Society, BP 3055, Yaoundé, Cameroon.