The Amphibians of the Yakassé-Mé Village Forest, a Threatened Rainforest of South-Eastern Ivory Coast
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Herpetology Notes, volume 7: 657-665 (2014) (published online on 12 November 2014) The amphibians of the Yakassé-Mé village forest, a threatened rainforest of south-eastern Ivory Coast N’Goran Germain Kouamé1,*, Jean Christophe B.Y.N. Konan2, Abouo Béatrice Adepo-Gourène2, Germain Gourène2 and Mark-Oliver Rödel3,* Abstract. We report on the amphibian fauna of the Yakassé-Mé village forest, south-eastern Ivory Coast. We recorded a total of 24 frog species. These frogs are typical for the rainforest and degraded rainforest habitats of this region. Some species which we expected, but were lacking from our records include the regional endemics Astylosternus laticephalus, Hyperolius viridigulosus, Morerella cyanophthalma, Phrynobatrachus ghanensis. Although the Yakassé-Mé village forest is only a relatively small forest remnant, we urge for its future protection as it represents an important refuge for the forest fauna in the south-east of Ivory Coast, where only few forests persisted until today. Keywords. Anura, biodiversity assessment, conservation status, Côte d’Ivoire, Upper Guinea hotspot. Introduction border, are amongst the most highly threatened African forests (Norris et al., 2010; Mayaux et al., 2013). They Whereas the amphibian fauna in Ivory Coast has been suffer from steadily increasing human encroachment, in intensively investigated in the forests in the West (e.g. particular logging, shifting agriculture and conversion Rödel and Branch, 2002; Ernst et al., 2006), the forest- of forests into plantations (Zadou et al., 2011). There is savannah mosaic in the Center (e.g. Lamotte, 1967; thus a clear need for basic faunistic studies. Some of the Barbault, 1967, 1972; Rödel, 2003; Rödel and Ernst, few remaining forests are possessed and managed by 2003; Adeba et al., 2010), as well as in the savannahs of villages. Published information on these village forests is the North (e.g. Rödel, 2000; Rödel and Spieler, 2000), sparse and difficult to access. The area around Yakassé- respective assessments for the eastern Ivorian forests Mé village, near Agboville, was covered by dense forest are rare (Assemian et al., 2006). This is troubling as the at least until 1965 (Schiøtz, 1967). Nowadays most of latter forests are not well known biologically, but seem the former rainforest has been converted into rubber and to be home for various endemic species, as implicated cocoa plantations (N.G. Kouamé, pers. obs.). We herein by some recent species discoveries (Rödel et al., 2009, aim to 1) provide an assessment of the species richness 2012). In addition the south-eastern Ivorian forests, and composition of the amphibian fauna of this village extending from Abidjan eastwards to the Ghanaian forest, and 2) add information on some little known species. Some data on one species, Hyperolius laurenti Schiøtz, 1967 have been published separately (Kouamé et al., 2014). As reptiles of this area are poorly known as well, we list our sightings in an appendix. 1 Jean Lorougnon Guédé University, Department of Biology and Animal Physiology, Daloa, BP 150, Côte d´Ivoire. Material and Methods 2 Nangui Abrogoua University, Laboratoire d’Environnement et Biologie Aquatique, UFR-SGE, 02 BP 801, Abidjan 02, Study area. The village forest of Yakassé-Mé is Côte d´Ivoire. situated app. 55 km north-east of Abidjan, Ivory 3 Museum für Naturkunde, Leibniz Institute for Evolution and Coast (05°45’32.8” - 05°47’10.4” N; 003°55’46.1” - Biodiversity Science, Invalidenstrasse 43, 10115 Berlin, Germany. 003°56′27.9’’ W; see Figure 1 in Kouamé et al., 2014). * Corresponding authors: [email protected], The lowland forest has a mean annual temperature of [email protected] 26°C; the mean annual precipitation is 2000 mm. The 658 N’Goran Germain Kouamé et al. Figure 1. Typical aspects of the habitats of the Yakassé-Mé village forest; a= logged forest in relatively good shape; b= gallery forest along stream; c= heavily degraded part of the forest (conversion into plantations); d= old cocoa plantation. major rainy season lasts from March to July. This is and YA3) or on the periphery (YA4) of the village forest. followed by a drier period from August to September While the first site (YA1) was mainly characterized and a minor rainy season lasting from October to by small gallery forests (Figure 1a), the second site November (Eldin, 1971). Field work was done at the (YA2) comprised dense vegetation, characterized by end of the core rainy season from 9-29 July 2013. The large canopy gaps and thick shrubby undergrowth with rivers Mé and Mafou cross the northern part of the small streams (Figure 1b). YA3 comprised heavily area. The Yakassé-Mé village forest mainly consists degraded forest parts, especially visible at the forest of moist, evergreen rainforest on predominantly sandy edges, which were often in direct vicinity to cocoa and soil. The vegetation is typical for south-eastern Ivorian rubber plantations (Figure 1c). YA4 mainly consisted of forests (Béligné, 1994). Large parts of this forest zone small forest islands, not far from the village, subsistence have been logged. Other parts of the forest have been farming, and a mosaic of rubber and cocoa plantations converted into rubber and cocoa plantations. Most parts (Figure 1d). Only smaller, inaccessible parts of the forest of our survey area, covering app. 100 ha, are currently stands seemed to be rather undisturbed. In appendix 1 & under active logging activities (Figure 1). 2 we provide a list of all sites, a short habitat description, We surveyed four general areas, called YA1 (25 ha), and check list of species and individuals encountered. YA2 (40 ha), YA3 (15 ha) and YA4 (20 ha) in the A hand-held GPS receiver (Garmin 12XL) was used to following. They were either located inside (YA1, YA2 record the geographical positions of all study sites. Amphibians of the Yakassé-Mé forest, Ivory Coast 659 Field work, sampling effort and vouchers. Amphibians calculated 25 (sd: ± 0.95) amphibian species, the Chao 2 were mainly located opportunistically while surveying estimator estimated 24 (sd: ± 0.09) species for the study all available habitats by two people. Surveys were area. We hence recorded almost the entire (96% and undertaken during day and night. Our searching 100%, respectively) estimated species richness. techniques included acoustic, visual scanning of terrain The species richness at the different sites was: 18 and refuge examination (e.g. lifting logs, peeling away species in YA1, 9 spp. in YA2, 11 spp. in YA3 and 13 bark, scraping through leaf litter). We searched for spp. in YA4. More than one third of the encountered frogs on 20 days, each day for seven hours (08:00 h- forest species (9 spp., 37.50%; Table 1) tolerated 11:00 h & 18:00 h-22:00 h GMT). The sampling effort farmbush habitats (degraded forest). Eight species therefore was always 14 person-hours per day and thus (33.33%) were very closely associated with forest comparable throughout the survey and all habitats. We habitats. Seven species (29.17%) exhibited a strong used the daily species lists in order to calculate the preference for savannah and farmbush habitats and are sampling efficiency. As our sampling design provides normally not occurring in pristine forests. only qualitative and semi-quantitative data we calculated Half of the species (12 spp.) do not occur outside West the estimated species richness, and thus the sampling Africa (defined as the area west of the Cross River in efficiency, with the Chao 2 and Jack-knife 1 estimators Nigeria; see Penner et al., 2011), and are often restricted (software: EstimateS, Colwell, 2005). These estimators to smaller parts of West Africa. Less than one third are incidence based, calculated with the presence/ (29.17%) of all recorded species only occur in the Upper absence data of the daily species lists (20 days of survey Guinea forest zone (forests west of the Dahomey Gap) work) for 24 amphibian species. To avoid order effects while only one species (Hyperolius laurenti, 4.17%) is we performed 500 random runs of the daily species endemic to a region from south-eastern Ivory Coast to lists. southern-central Ghana. After capture, frogs were determined to species level, According to the IUCN Red List, about one fifth of all measured, sexed and mostly released in their habitat. recorded species are threatened: three species are Near The nomenclature used herein follows the taxonomy by Threatened (Afrixalus nigeriensis, Phrynobatrachus Frost (2014). Snout-urostyle-lengths of the living frogs alleni and P. phyllophilus), one is Vulnerable were taken with a dial calliper (accuracy ± 0.5 mm). (Hyperolius laurenti) and one, Hylarana occidentalis, Some vouchers were euthanized in a 1,1,1-Trichloro-2- is listed as Endangered (IUCN 2013; Table 1). methyl-2-propanol hemihydrate solution and thereafter preserved in 70% ethanol. Voucher specimens are Notes on selected species. Below we provide some deposited in the research collection of N.G. Kouamé additional data on selected species (for details on at the Jean Lorougnon Guédé University, Daloa, Ivory Hyperolius laurenti, see Kouamé et al., 2014). Coast. Afrixalus nigeriensis (Schiøtz, 1963) (Figure 2a) is a West African forest species found mostly in primary Results rainforest (Schiøtz, 1967, 1999; Rödel and Branch, We recorded a total of 24 frog species in the Yakassé- 2002), although it can be rarely encountered in degraded Mé village forest (Table 1). The records for Hyperolius forests as well (Hillers and Rödel, 2007). The species concolor and the reptile species (see appendix) are based reaches its western limit in Liberia (Hillers and Rödel, on observations only. For all other species we deposited 2007). This survey is the first recent confirmation of the vouchers at the Jean Lorougnon Guédé University, species’ presence in the eastern forests of Ivory Coast.