Home range area may vary considerably in relation to habitat contamination in two African terrapins from pristine and oil polluted habitats

Abstract

AbstractHome range and nesting habitat were studied in two sympatric pelomedusid terrapins (Pelusios niger and Pelusios castaneus) from two study areas in the Niger Delta (Nigeria, West Africa), one with pristine habitat conditions and one which was polluted by a oil spill event some years before. Seventy-seven individuals (38 P. niger and 39 P. castaneus) were radiotracked, each for more than 60 days, and their home range was calculated by the minimum convex polygon method, with 95% of the point locations per individual. The mean home range size of females was significantly larger in the polluted area than in the pristine area in both P. niger and P. castaneus, and the mean home range size of female P. niger was significantly larger than that of female P. castaneus in the polluted area, but not in the pristine area. The mean home range size of males was significantly larger in the polluted area than in the pristine area in P. niger but not in P. castaneus, and the mean home range size of male P. niger was significantly larger than that of male P. castaneus in the polluted area but not in the pristine area. Radiotracked females of both species showed a clear preference for nesting sites situated along ponds and not along the banks of the river, on sandy soil, often with abundant vegetation around. Some females of both species deposited their eggs at greater distances from water bodies in the polluted area than in the pristine area. The comparative evidence of these patterns indicates consistent responses of the two species to the altered habitat, which further supports the general hypothesis that habitat pollution has seriously affected the ecological strategies of these terrapin species.