Ecological correlates of the distribution of terrestrial and freshwater Chelonians in the Niger Delta, Nigeria: A biodiversity assessment with conservation implications

Distribution and ecology of freshwater and terrestrial Chelonians were stud ied in eastern Niger Delta of Nigeria. Fifty-two study areas, sparsely dist ributed along the hydrographic basins of the main rivers and in the main en vironmental types available in the region, were carefully surveyed over mor e than two years. Seven Chelonian species were found; four of them (Pelomed usa subrufa olivacea, Pelusios c. castaneus, Kinixys belliana nogueyi, Kini xys erosa) were recorded for the first time inside the Niger Delta region. P. castaneus, P. niger, and K. homeana appeared to be common, whereas K. be lliana was extremely rare. In general, species were recorded mainly from th e areas characterized by dominant deltaic swamp forest, but the distributio n of P. castaneus exceeded by far the distribution of this habitat in the s tudy region. A statistical model (based on logistic regression method) was applied to evaluate the effects of the macro-environmental variables on the local distribution of the various species. It resulted that a determinant factor for the presence of the species was: (i) the presence of Primary Dry Forest for P. castaneus and P. niger; (ii) the presence of Secondary Dry F orest for PC homeana, but the presence of both Shrubland and Farmland/Plant ation was not determinant for the presence of any species; (iii) the presen ce of Primary Swamp Forest for P. niger: (iv)the presence of Secondary Swam p Forest for P. subrufa, K. erosa, and K. homeana: (v) the presence of Mang rove Formations for Fl niger and K. homeana; (vi) the presence of Permanent Big Water-Bodies (rivers, creeks) for P. subrufa. The combination of Prima ry Dry Forest and Secondary Swamp Forest would be determinant for the prese nce of live of seven species, thus demonstrating to be a crucial combinatio n of habitats from the conservationistic point of view. Principal Component Factor Analysis classified the seven Chelonian species and the eight macro -environmental parameters into five groups: (I)a group formed by P. subrufa and K. belliana; (2)a group formed by the macro-environmental parameters " Shrubland" and "Farmland/Plantation"; (3) a group, relatively close to the group IZ!, formed by the macro-environmental parameters "Secondary Dry Fore st" and "Secondary Swamp Forest", and by the species K. erosa and K. homean a; (4) a group formed by the macro-environmental parameters "Primary Dry Fo rest", "Primary Swamp Forest", and "Permanent big Water Body", and by the s pecies Fl castaneus, P. niger, and Trionyx triunguis; (5) a group formed by the macro-environmental parameter "Mangrove" alone. Phenology data suggest ed that only one of seven, if any, species could aestivate during the dry s eason: P. subrufa.