Introduction

With at least 20 different taxa, Côte d'Ivoire has a high primate diversity. Most of these taxa are listed as threatened on the IUCN Red List (IUCN 2006), and three are among the world's 25 most threatened primates — Cercocebus atys lunulatus, Cercopithecus diana roloway, and Procolobus badius waldronae (see Mittermeier et al. 2006), the last considered already extinct by Oates et al. (2000), although new evidence suggests that it still survives (McGraw 2005). Most studies on primates in Côte d'Ivoire have focused on the western part of the country, especially the Taï National Park (for example, Noë and Bshary 1997; Wachter et al. 1997; Boesch and Boesch-Acherman 2000). Long-term field studies are still underway in the Taï forest, including the Taï Monkey Project (TMP) and the Taï Chimpanzee Project (TCP). Surveys for C. diana roloway and P. badius waldronae have been conducted in the eastern part of the country (McGraw et al. 1999; Oates et al. 2000), but only a few studies have focused on central Côte d'Ivoire, between the Bandama and Sassandra rivers. This region is of special interest because it is a zone where ranges of related taxa (including primates) overlap and where hybridization may occur (Kingdon 1997).

There are two species of black-and-white colobus in West Africa, Colobus polykomos (Zimmerman, 1780), the king or western pied colobus, and C. vellerosus (I. Geoffroy, 1834), the ursine or Geoffroy's pied colobus (see Oates and Trocco 1983; Oates et al. 1994). Both occur in Côte d'Ivoire (Fig. 1). Colobus vellerosus ranges from the Bandama River to western Nigeria (Oates et al. 1994; Kingdon 1997). Colobus polykomos ranges from Guinea to the Sassandra River in western Côte d'Ivoire (Napier 1985; Oates et al. 1994; Groves 2001).

Figure 1.

The approximate distribution of West African black-and-white colobus monkeys in West Africa and in Côte d'Ivoire. Rivers suggested as geographic barriers for a number of species and survey sites are also indicated (1 = Marahoué; 2 = Niégré; 3 = Bolo West; 4 = Dassiéko).

The form dollmani, Dollman's colobus, was first described by Schwarz (1927) as a subspecies of Colobus polykomos (the single species of black-and-white colobus that he recognized; see Schwarz 1929), occurring east of the Sassandra River in the narrow strip extending to the Bandama River. Colobus p. dollmani differs from C. p. polykomos by coat pattern, and especially by a white band on the thighs; a characteristic of C. vellerosus. While dollmani continues to be referred to by some authors as a subspecies of polykomos (see for example, Napier 1985; Kingdon 1997), the recognition of C. vellerosus as a valid species (distinct from polykomos) by Oates and Trocco (1983; see also Grubb et al. 2003), and its closer resemblance to C. vellerosus, led Groves (2001) and Grubb et al. (2003) to refer to it as C. vellerosus dollmani, and as a junior synonym of C. vellerosus.

Dandelot (1974) pointed out that “Booth (1954) observed interbreeding between [the subspecies] vellerosus and dollmani in the Bouaflé Forest Reserve” (p.30), and that Rahm (1970) had supposed dollmani to be a hybrid between vellerosus and polykomos. Groves et al. (1993), Oates (1996), Kingdon (1997), Groves (2001, 2005) and Grubb et al. (2003) all consider it to be a hybrid between C. polykomos and C. vellerosus. Groves (2001, 2005) and Grubb et al. (2003) listed it as a junior synonym of C. vellerosus. It is not known, however, whether it constitutes a consistent morphotype or whether there are local populations that differ according to the degree of gene influx from C. polykomos or C. vellerosus. A number of studies have focused on aspects of the socioecology of C. polykomos (see Moresco-Pimentel 1994; Nijssen 1999; Bitty 2001), but information on C. p. dollmani is still scarce.

The primates in Côte d'Ivoire are threatened by hunting for bushmeat and the clear-cutting of forest for agriculture. Colobus p. dollmani is endemic to the forests of Côte d'Ivoire, occupying just a small range from the Sassandra River to the Bandama River. This and our ignorance of its status make it particularly vulnerable to extinction. For this reason we carried out surveys to obtain an assessment of the general status of primates in central Côte d'Ivoire, between April 2003 and October 2004, in Dassioko, Bolo West, and Niégré forest reserves and Marahoué National Park, focusing especially on C. p. dollmani. We also interviewed people whenever we could on the presence and absence of all the primates with ranges extending into central Côte d'Ivoire, including, besides C. p. dollmani, Perodicticus p. potto, Cercopithecus (c.) lowei, Cercopithecus p. petaurista, Cercopithecus (diana) roloway, Chlorocebus (aethiops) sabaeus, Cercocebus atys lunulatus, Papio anubis, Procolobus verus, Procolobus b. badius, and Pan troglodytes verus. Galagoides demidoff and Galagoides thomasi are also expected to occur in southern Côte d'Ivoire, but we neither looked for them in particular nor did we ask about them in the interviews.

Methods

Prior to our survey, we consulted relevant literature from the Société de Développement des Forêts en Côte d'Ivoire (SODEFOR 1996; Anonymous 1999) to learn more of the historical distribution of C. p. dollmani and the status of the forests and their wildlife. Previous studies in the protected areas of Côte d'Ivoire noted the presence of C. p. dollmani in Marahoué National Park, and Bolo, Dassiéko, and Niégré forest reserves (Fig. 1). Relying on this information, we started our investigations in these forest reserves and provisionally treated all black-and-white colobus monkeys from the region between the Sassandra and Bandama rivers as C. p. dollmani. We interviewed people (particularly hunters)) in the nearby villages, asking them to describe the primates they knew and to mimic their calls. We showed them photographs or paintings of the species afterward to confirm their identifications. We gathered information about the past and recent presence of primates, particularly C. p. dollmani, in the forest reserves and in neighboring forest fragments. We also visited a number of restaurants in these villages to gather information on primate species being offered as bushmeat.

We surveyed on foot, walking slowly and quietly along old logging roads and existing paths at about 1–1.25 km/hour for an average of 10 hours per day. During that time, we walked the paths repeatedly, noting any visible or acoustic sign of the presence of primates, and determining their position with a global positioning system. Primates in these forests are hunted and therefore shy, and we were usually unable to approach them closer than about 50 m. We began early in the morning at 06:00 and continued until 13:00. After an hour's rest, we continued the survey until 18:30. We collected fecal samples of Cercopithecus (c.) lowei, Cercopithecus p. petaurista, Cercocebus atys lunulatus, and C. p. dollmani for genetic analysis. Once a group of monkeys was detected we stayed with it and observed it for as long as we could. We used Kingdon (1997) for the identification of species and subspecies.

Because we noted mainly just presence-absence, our survey method did not allow for reliable estimates of population densities. We distinguished two reliability levels concerning our data. A taxon was classified as present in a certain forest reserve if we saw or heard it directly or if we found it on sale as bushmeat in nearby villages. A taxon was classified as most likely present if it was mentioned only as present in interviews. Furthermore, we defined three population density categories: a species was considered frequent when it was detected at least once a day during the survey; rare when observed occasionally or at least once in three days of survey or found as bushmeat in the restaurants; and very rare when it was not encountered during the survey, but its presence was reported by hunters (seen in last 12 months).

Survey sites

The location of the survey sites is shown in Figure 1. The Dassiéko Forest Reserve (11 ,317 ha) is situated between the towns of Fresco and Sassandra (5°02′44′N, 5°48′19′W). In 1990, this forest was divided into Dassiéko South (7,980 ha) and Dassiéko North (3,337 ha) by a road. The road improved access to the forest's interior and enhanced forest destruction. The conservation status of Dassiéko South seems to be better than the northern part. The Bolo Forest Reserve is north of the Dassiéko Forest, between 5°07′ and 5°26′N and 5°47′and 6°03′W. It is made up of three forest blocks: Haute Bolo (18,750 ha), Bolo West (7,700 ha), and Bolo East (14,306 ha). The Niégré Forest Reserve (97,300 ha) is in the northwest of Côte d'Ivoire. The coordinates for the center of this forest are 5°20′N, 6°10′W. The Dassiéko, Bolo, and Niégré forests belong to the Guinean domain, and include dense and marshy forests, and marshy, evergreen coastal forests with coastal lagoons, swamps, marshes, and mangroves.

Marahoué National Park (101 km²) has a relatively undulating terrain, drained in the southeast by the Bandama Rouge (Marahoué River) and its tributaries. This reserve is notable for its geographic location, with Guinean savannah woodlands in the east and northeast, and dense deciduous forest and some gallery forest in the south and southeast. This was the only site where we expected to find Chlorocebus (aethiops) sabaeus and Papio anubis, because the other three are to the south, and outside the known range of these two species.

In total, we spent 14 days and 10 nights in the Bolo West forest during the rainy season in May 2004, and 6 days and 5 nights in the Dassiéko South forest in July 2004. Three days were spent in Baleko Brousse, a village bordering the Niégré Forest reserve, and 13 days and 7 nights in the Niégré forest in April 2004. We did surveys on 16 days and 8 nights in various parts of the Marahoué National Park during the dry season in December 2003. See Table 1 for the precise dates.

Table 1.

Presence of primate taxa in three forest reserves (Dassiéko, Bolo West, and Niégré) and the Marahoué National Park between the Sassandra and the Bandama rivers, Côte d'Ivoire.

Results

According to the criterion “directly seen or heard or found among bushmeat,” we were able to confirm the presence of eight of the 13 possible primate taxa during our surveys in at least one of the four protected areas (Table 1). They were: Perodicticus p. potto, Cercopithecus (c.) lowei, Cercopithecus p. petaurista, Cercocebus atys lunulatus, Papio anubis, Procolobus verus, and Colobus polykomos dollmani. We did not see Cercopithecus (diana) roloway, Procolobus b. badius, and Pan troglodytes verus, although local people indicated that Cercopithecus (diana) roloway and Pan troglodytes verus were present in all four of the reserves. Procolobus b. badius was reported only for Dassiéko.

The presence and frequency of sightings of these eight primates varied among the reserves. Perodicticus potto was found being sold as bushmeat, and interviewees reported its occurrence at all four sites. Papio anubis, a savanna species, was found in Marahoué National Park but not in the southern forest reserves which are out of its known range. Similarly, Chlorocebus aethiops sabaeus, another savanna species, was reported as present only for Marahoué National Park during interviews.

Discussion

During our survey, we gathered presence-absence information on 11 primate taxa, Perodicticus potto, Cercopithecus (c.) lowei, Cercopithecus p. petaurista, Cercopithecus (diana) roloway, Chlorocebus (aethiops) sabaeus, Cercocebus atys lunulatus, Papio anubis, Procolobus verus, Procolobus badius badius, Colobus polykomos dollmani, and Pan troglodytes verus, in four forest reserves between the Sassandra and the Bandama rivers in southern Côte d'Ivoire. We were able to confirm the presence of just three of these in all four of the protected areas we visited: Cercopithecus (c.) lowei, Cercopithecus p. petaurista, and Procolobus verus. From the numbers of encounters we could infer that the two guenons were the most abundant of the diurnal primates in these reserves. Although we recorded Cercocebus atys lunulatus in Dassiéko, we had only the reports of hunters as evidence for its permanence in the other three sites.

Indirect evidence suggested that another three taxa still occur in the four areas: Perodicticus potto, Cercopithecus (diana) roloway, and Pan troglodytes verus. The status of Perodicticus potto was difficult to assess due to its nocturnal activity and we might have overlooked it during our diurnal surveys. However, even this species was found among bushmeat in the markets, and its number may also be decreasing rapidly. Pan troglodytes verus was detected in only one reserve (Dassiéko), but reported by interviewees for the other three sites. Chimpanzees have been the focus of conservation efforts in the Taï National Park, but less attention has been given to other populations in the region. Given their rarity and low population sizes, they will soon go extinct in the forest reserves if no immediate conservation action is taken. In 2004, The Wild Chimpanzee Foundation (WCF) has begun a number of initiatives, particularly in Marahoué, Banco National Parks.

We found no evidence for the presence of Procolobus badius badius in any of the four reserves. Poachers living in the vicinity of Dassiéko informed us that its disappearance was recent, and it would seem to be due to hunting, rather than habitat loss. Papio anubis and Chlorocebus (aethiops) sabaeus occur only in Marahoué National Park which, unlike the three forest reserves, consists of a mosaic of Guinean savannah woodlands and dense deciduous forest. The two dwarf galagos, Galagoides thomasi and Galagoides demidoff might be present in the reserves, but we do not have any information about their status.

The main aim of our survey was to gather information about the status of Colobus p. dollmani in the interfluvial region of Côte d'Ivoire; its historical range. It was observed in only one of the four sites, Bolo Forest Reserve — and just one group was found — evidently very low numbers. Local people said that it occurred at the other four sites, but the last report in the Marahoué National Park was in 2002. No information was available for this colobine subspecies prior to our study, and its restricted range compared with that of the other black-and-white colobus monkeys, the destruction of its habitat, and hunting pressure could lead to its extinction in the near future. According to Oates and Trocco (1983), Groves et al. (1993), Groves (2001), and Grubb et al. (2003), C. p. dollmani is most likely a hybrid form of C. polykomos × C. vellerosus, both of which are already on the IUCN Red List of Threatened Species (IUCN 1994, IUCN 2006): Colobus polykomos is listed as Lower Risk/Near Threatened, and Colobus vellerosus as Vulnerable. A more recent assessment (resulting from a status assessment workshop held in Orlando, Florida, 27–30 January 2005, and using the IUCN [2001] criteria) has yet to be incorporated into the IUCN Red List, but places both species as Vulnerable (Hoffmann 2006).

Colobus p. dollmani is not included on the Red List because it is regarded as a hybrid and a synonym of C. vellerosus. Genetic analyses are necessary to clarify its taxonomic status and to estimate the degree of genetic exchange with its possible parent species and whether the population is monophyletic or paraphyletic. It is also important to determine whether its morphotype varies locally or whether it is consistent over its range. We would argue that even if it is a hybrid form, it is worthwhile preserving it — it is an evolutionary unit and possibly undergoing speciation. A comparable situation exists for the West African scaly-tailed squirrel, Anomalurus pelii, where different subspecies are recognized to the east and west of the interfluvial region, and the form between the Sassandra and Bandama rivers was recently recognized as a distinct, third subspecies (Schunke and Hutterer 2005).

The conditions of the four reserves in southern Côte d'Ivoire are not good. Only Dassiéko South was found to be relatively undisturbed — most likely at least in part an effect of a long-term ecological monitoring project there. The frequent presence of researchers in the forest might be discouraging potential poachers and farmers to hunt and farm the forest. The other three reserves have numerous clearings made by farmers, and only a very few parts remain undisturbed. There are camps, small villages, and many people in these forest reserves. In February 2005, the illegal camps and villages inside Marahoué National Park were destroyed, and the people were forced to leave the park.

Hunting is a major threat to primates and other wildlife in these forest reserves. Although wildlife is legally protected, there is almost no control of poaching. The first concern of the managers of forest reserves in Côte d'Ivoire is forestry, and not the protection of wildlife. Civil unrest in Côte d'Ivoire since 2002 has created social and economic instability, and the protection of forests and wildlife is not currently a priority for the government. People have taken advantage of this and there have been dramatic increases in encroachment in these supposedly protected forests. The National Protected Areas Management Program (PCGAP), a project funded by the European Development Fund (EFD), World Wildlife Fund, Agence Française de Développement, the Global Environment Facility (GEF), and Kreditanstalt für Wiederaufbau (KfW), was ceased pre-term, and the resulting benefits of forest management and protection have been lost, with a corresponding upsurge of illegal forest clear-cutting and poaching. There are now numerous cocoa plantations, forest clearings, trails, snares, and poacher camps even in the remotest parts of the forests.