TAXONOMIC REPORT ON SMALL MAMMALS FROM TWO COASTAL WETLAND (RAMSAR) SITES IN GHANA

Surveys of the small mammal populations of two coastal wetlands in Ghana, Muni-Pomadze (Central Region) and Keta (Volta Region), were undertaken over a 1-month period as part of an assessment of the ecological status of these wetlands. The study investigated aspects of the ecology of the small mammals, which are known indicators of habitat (environmental) quality. The methodology involved live-trapping of the terrestrial small mammals (rodents and insectivores) using collapsible Sherman traps (for smaller species) and National (Tomahawk) traps (for larger species). Bats were also live-trapped using mist nets at Muni-Pomadze only. A total of 11 species of small mammals were recorded at Muni-Pomadze, comprising 47 individuals of seven rodent species, four individuals of two insectivore species and two individuals of two bat species. Four species were recorded at Keta, made up of three individuals of two species of insectivores and eight individuals of two rodent species. Generally, majority of all the adult individuals captured at Muni-Pomadze were in reproductive condition. At Keta, most of the captures were sub-adult females, and only one of two males captured was in reproductive condition (scrotal testes). The grassland/thicket habitat at MuniPomadze was the most diverse, probably because the thicket “islands” provided shelter from potential predators, which were themselves scarce because of the openness of the habitat. The Keta Ramsar site was characterised by low abundance and diversity, attributable to human settlement and economic activity. A taxonomic report on the captured small mammal species is provided. Introduction Field baseline surveys of the small mammal populations of two coastal wetlands (Muni-Pomadze and Keta) in Ghana were undertaken during June and July, 1997 with the main objective of ascertaining the status of such wetland communities, as well as updating current species lists in selected protected areas in Ghana. Generally, information on small mammal diversity of Ghana’s coastal Ramsar sites has been virtually non-existent, despite the important roles such mammals play in the socio-cultural life of the communities, as well as their importance as indicators of habitat quality. For example, large rodents such as grasscutters (Thryonomys swinderianus) and giant rats (Cricetomys gambianus) are hunted for subsistence as well as for economic purposes (bushmeat) (Ryan & Attuquayefio, 2000). Even though there have been previous accounts of the systematics and distribution of the mammals of Ghana (Ingoldby, 1929; Cansdale, 1948; Booth, 1956; 1959), most of these have not been updated since they were published several years ago. It is, therefore, imperative to conduct as many surveys as possible, especially in previously unsurveyed areas like wetlands, in order to build up a badly-needed updated and comprehensive checklist of mammals for the whole country with time (Decher, 1997). For example, Booth’s (1959) previous checklist of mammals of the Accra Plains has recently been updated by Decher (1997). The surveys were undertaken as a collaborative effort involving the Zoology Department of the University of Ghana, Hobart and William Smith Colleges of New York, USA, and the Wildlife Division of the Ghana Forestry Commission, as part of a wider Coastal Wetlands Management Project (CWMP) commissioned by the Global Environmental Facility (GEF) of the World Bank. The ultimate objective was to provide the requisite scientific database that would lead to an increased understanding of the species diversity of the coastal regions of Ghana (Piersma & Ntiamoa-Baidu, 1995) as a basis for developing effective management strategies for such wetlands. The specific objectives were to (i) conduct complete small mammal field surveys of two coastal Ramsar sites (Keta and Muni-Pomadze) in Ghana, (ii) identify and determine the distribution and abundance of endemic and/or rare species and species of conservation concern with regard to their habitat associations, and prepare voucher specimens of the collections for accurate taxonomic identification and reference. This paper reports on the results of the survey, with species accounts covering reproductive condition and morphological measurements, supplemented with notes on distribution and taxonomy of the mammals inhabiting the two survey sites. Study areas Muni-Pomadze Ramsar site (05 19’ N; 00 40’ W). The site, located in the Central Region of Ghana, about 56 km west of Accra, covers a total management area of 90 km surrounding the shallow coastal Muni Lagoon, which has an area of 3 km and maximum depth of 1.5 m (Fig. 1). There were five survey localities within the Muni-Pomadze Ramsar site (Fig. 2). Fig. 1. Location of Muni-Pomadze and Keta Ramsar Sites, Ghana