Community Characteristics of Sympatric Freshwater Turtles From Savannah Waterbodies in Ghana

Abstract

Despite increasing pressures on freshwater resources worldwide, and the threatened status of most freshwater turtles, there is still limited knowledge of habitat use and niche partitioning in Afrotropical freshwater turtle communities. In this study, we describe habitat associations, community diversity, and temporal patterns of occurrence of freshwater turtle species in the Dahomey Gap ecoregion of Ghana (West Africa). We gathered data from 13 sites in central Ghana and along the Sene Arm of Lake Volta in the Digya National Park (Bono East Region). We employed opportunistic short-term surveys (at seven sites) together with longer-term (six-months duration) standardized evaluations of turtle presence and numbers in different habitats (at six sites). In addition, we interviewed fishers in the Lake Volta area to explore their perception about turtle abundance trends. Overall, 210 turtle individuals belonging to four species (Trionyx triunguis, Cyclanorbis senegalensis, Pelomedusa sp. and Pelusios castaneus) were recorded; for 139 individuals the precise capture sites and habitat type were recorded, whereas 71 individuals were observed in market places and were not considered in our analyses. We observed three sympatric species at the local scale of the various study sites. In each site, the dominant species was either C. senegalensis or Pelomedusa sp. However, Pelomedusa sp. was the most abundant species in temporary waterbodies whereas C. senegalensis was more numerous in permanent ones. A Multiple Correspondence Analysis visualized that, in permanent waterbodies all species were associated with similar physical habitat variables. C. senegalensis and T. triunguis were more abundant in localities containing woody emergent vegetation and inorganic substrate. In a Canonical Correspondence Analysis, we show that the density of herbaceous emergent vegetation was more important for P. castaneus than for C. senegalensis. Interviews with local people suggested that freshwater turtles do not have any special marketing interest for them, but that overfishing may have considerably affected the population density of these semiaquatic reptiles. Overall, Comparisons of diversity metrics between our study areas and previous literature revealed that turtle community composition was substantially the same, both qualitatively and quantitatively, all throughout the savannahs of West Africa.

Patterns of diversity, species richness and community structure in West African savannah small mammals (rodents and shrews)

“…Also recent studies from Ghana and Benin revealed a number of species (in Ghana 3 for shrews and 12 for rodents; in Benin 2 for shews and 10 for rodents) that is consistent with our analyses (Nicolas et al 2020;Decher et al 2021), and the same is true for rodent communities in Malawi (9 sympatric species; Happold and Happold 1991). Interestingly, a relatively stable number of sympatric species per site was also seen in turtles from West African savannahs (Gbewaa et al 2021), thus suggesting that the ecological conditions of the various West African savannah sites are functionally similar and support a inter-site similar number of sympatric species although not necessarily the same taxa.…”