Distance-generated field density estimates for the threatened sahel tortoise centrochelys sulcata

In this paper, the results of the first density investigations (via Distance methodology on line transect surveys) for the threatened African spurred tortoise Centrochelys sulcata from West African Sahel (Niger and Burkina Faso) are reported. Spurred tortoises were encountered in 51.8% of Burkina Faso transects (n = 27) and in 60.7% of Niger transects. In several transects we found evidence of the tortoise presence, but without actually seeing any individual. Pooling all the transects from which tortoise density was calculated, the mean density of tortoises in Burkina Faso was 0.0021 ind./ha, and in Niger was 0.167 ind./ha. Nonetheless, there was a considerable variability in density estimates by transect in both countries, and especially in Teneré-Termit (Niger), the density of tortoises was very high (over 2 ind./ha). Teneré-Termit region in Niger may therefore represent a potentially crucial area for the conservation of this declining species.