Anuran surveys in south-western Nigeria SALAMANDRA 45 1 1-14 Rheinbach, 20 February 2009 ISSN 0036-3375 Anuran surveys in south-western Nigeria Abiodun B. Onadeko & Mark-Oliver Rödel Abstract. We report on the results of amphibian surveys in three south-western Nigerian states: Lagos, Ogun and Oyo. In total, we recorded between 35 and 38 species. The number of species per state ranged from 22 to 29. Most species were typical farmbush or savanna frogs. Although the overall species richness was comparatively low and only a few species were forest specialists, we observed a surprising number of frogs that could not unambiguously be assigned to described species. This was especially true of the gene- ra Leptopelis and Phrynobatrachus. Whereas some of these taxa (Leptopelis cf. macrotis, Phrynobatrachus cf. liberiensis) seem to indicate closer relationships between south-western Nigeria and the Upper Guinea forests, other findings (the eastern variation of Phlyctimantis boulengeri, Nectophryne afra) indicate the opposite geographic relation. The position of the study sites between the diversity hotspots of Upper and Lower Guinea would suggest high anuran diversity. We failed to record such a high diversity, but possibly found species from both areas and probably undescribed taxa (Phrynobatrachus sp., Leptopelis sp.). We believe that the high amount of degraded and converted natural forests may have already resulted in an impoverished anuran fauna. Remarkable and even new species may have survived in some of the small remaining forests. Intensive surveys and sustainable conservation of the remaining forests of south-wes- tern Nigeria is therefore highly recommended. Key words. Amphibia, distribution, diversity, biology, forest, new records, savanna. Introduction of West and Central African species alike. So far, about 03 amphibian species, 0 anurans With 30-40 million people, Nigeria is the and two caecilians, have been recorded from most densely populated African country. within Nigeria’s borders (IUCN et al. 2006). The high human population with the result- This is astonishingly few, compared to the ap- ing pressure on natural habitats, as well as the proximate 200 species of neighbouring Cam- country’s position of being the twelfth largest eroon (LeBreton 999, Frétey & Blanc producer of oil, has resulted in a remarkably 2000, IUCN et al. 2006, J.-L. Amiet pers. high proportion of degraded and converted comm.). However, it is questionable whether land (www.en.wikipedia.org/wiki/Nigeria; Cameroon is really that much richer in am- latest accessed 4 May 2007). In contrast, Ni- phibian diversity or if simply Nigeria is less geria also comprises a great variety of ecosys- well explored. tems, ranging from mangrove swamps and Many contributions to the knowledge rainforests along the coast, various types of of the country’s amphibian fauna date back savanna further north, to finally the Jos-Pla- to the sixties of last century (Schiøtz 963, teau in Central Nigeria and the south-eastern 966, 967, Walker 966, 967, 968, 969) or region towards Cameroon offering moun- even earlier (Sanderson 936, Romer 953). tainous habitats. From a biogeographic point Due to long lasting political unrest, with the of view, Nigeria is situated between West and exception of a few papers (Akintola 976, Central Africa, and hence between the bio- Reid 987, Böhme & Nikolaus 989, Reid et diversity hotspots of the Upper and Lower al. 990) not much has been published on Ni- Guinea forest regions (Bakarr et al. 2004). gerian amphibians for the last decades. With- Consequently, Nigeria might be expected to in the last five years several papers on Nige- harbour high biological diversity composed rian amphibians have appeared again, mainly © 2009 Deutsche Gesellschaft für Herpetologie und Terrarienkunde e.V. (DGHT) http://www.salamandra-journal.com 1 Abiodun B. Onadeko & Mark-Oliver Rödel Fig. 1. Geographic positions of the study sites in south-western Nigeria (compare Appendix 1). dealing with the Cross River region and the ger, Chad and Cameroon. The Federal Re- area of the oil rich Niger Delta, including the public comprises 36 states and the Federal respective environmental problems (Eniang Capital Territory. We investigated the anuran & Luiselli 2002, Lea et al. 2003, 2005, Aka- fauna of three south-western states: Lagos, ni et al. 2004). Ogun and Oyo. Lagos, also comprising the However, still little is known about the sys- homonymous commercial capital, is situat- tematics, distribution and especially biology ed between 6.4-6.7°N and 2.7-4.6°E. Ogun of Nigerian amphibians. Remarkable excep- extends between 6.3-7.8°N and 2.7 4.6°E; tions are the contributions on frog parasites and Oyo extends between 7.-9.2°N and 2.7- by Aisien et al. (e.g. 200, 2004). Nigeria has 4.56°E. Nigeria is characterised by a South- lost the large majority of its rainforests and North gradient of precipitation. This is mir- most of its natural savanna habitats (UICN rored by a gradient of vegetation zones, nat- 996). We know that already minor alteration urally from tropical humid evergreen forests of natural forest ecosystems in West Africa in the South, gradually transforming into dry may result in drastically altered amphibian savannas in the North. assemblages, including the loss of many for- Along the south-western Nigerian coast est specialists (Ernst & Rödel 2005, Ernst there is a belt of mangrove swamps which et al. 2006). Hence, an increased effort to as- naturally do not harbour any amphibians. sess herpetofaunistically unknown parts of However, some species can be recorded just Nigeria seems extremely pressing. The pri- a few metres from the brackish waters, where mary aim of this paper is to present the am- this habitat is replaced by freshwater swamps. phibian results gained throughout several Such areas were located at Ikorodu, Badore, surveys undertaken by one of us (ABO) in Badagry and parts of Epe (all Lagos state). the south-western part of Nigeria. North of these swamps, a forest belt does naturally occur. These forests can be divided into rainforest and mixed deciduous or dry Study areas forest. Unfortunately, these forests have been heavily degraded, fragmented and convert- Nigeria covers an area of 923,768 km² and is ed by many anthropogenic activities, main- bordered by the Atlantic Ocean, Benin, Ni- ly cultivation for agriculture. The remaining 2 Anuran surveys in south-western Nigeria 40 350 40 350 35 300 35 300 30 30 250 250 C) 25 C) 25 (° (° 200 200 20 20 150 150 15 15 temperature temperature precipitation (mm) 100 precipitation (mm) 100 10 10 5 50 5 50 0 0 0 0 a Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec b Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 40 450 40 300 35 400 35 250 350 30 30 300 200 C) 25 C) 25 (° (° 250 20 20 150 200 15 15 temperature 150 temperature 100 precipitation (mm) precipitation (mm) 10 10 100 50 5 50 5 0 0 0 0 c Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec d Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Fig. 2. Monthly rainfall (black triangles) and monthly average maximum (open squares) and minimum (open circles) temperatures in a) Ijebu-Ode (data from 2003), b) Ikeja (2003), c) Ibadan (2003) and d) Ilorin (2002). forests hence mostly comprise secondary or Climatologically, the three states are charac- tertiary vegetation, characterised by dense terised by a rainy season from April to Oc- undergrowths and an open or broken cano- tober and a dry season from November to py. Farmland, secondary and tertiary forests March. The climate of four south-western Ni- were encountered at Ikorodu, Ogijo, Ishara, gerian towns is summarized in Fig. 2. Ijebu Oru, Ikenne, Onidundun and Fiditi. There only a few pockets of primary or near primary forest were left. Further north, this Material and methods zone is replaced by natural and derived sa- vanna, partly comprising a forest-savanna Our surveys were performed between July mosaic, especially where cultivation is less 2003 and December 2004. The most intense dominant. Examples from this zone were survey time was during the rainy season Onidundu, Fiditi, Oolo, Ibapon Oyewale and which at the same time is the breeding pe- Ogbomosho. The northernmost collection riod of most amphibian species. Between two sites were situated in the moist woodland sa- and four people were engaged in surveying. vanna zone (Guinea savanna), characterised Surveys were normally undertaken during by tall grass with fire resistant trees. Collec- the morning and evening hours. Geographic tion in this zone was done in areas north of positions were taken with a hand-held GPS Ogbomosho, including Gambari and Otte- receiver (Garmin eTrex). A short habitat Egba, an area close to Ilorin. characterisation was noted for each location A list of all study sites including a short investigated and all anurans were registered habitat description is given in Appendix . along with their respective habitats and loca- 3 Abiodun B. Onadeko & Mark-Oliver Rödel Tab. 1. Amphibian species recorded in Lagos, Ogun and Oyo States and number of sites where the respective species have been recorded (compare Appendix 1). Taxon Lagos Ogun Oyo Pipidae Silurana tropicalis 7, 9, 0 3, 9, , 2 Xenopus muelleri 4, 8, 9, 0 2, 3, 2, 6, 0 Hemisotidae Hemisus cf. guineensis 9 , 3, 0, H. marmoratus 2, 3, 7 Bufonidae Amietophrynus maculatus 2, 3, 6-0 -2 -2, 4-8, 0, A. regularis -4, 3, 4, 6, 8, 0 -3, 5-7, 9-2 2, 3, 5-8, 0, Nectophryne afra Dicroglossidae Hoplobatrachus occipitalis , 5, 8- 2-5, 0, , 2, 5, 6, 8 Ranidae Hydrophylax albolabris 7, 9 2, 8, 0, 2 H.