Surveys of basking map turtles Graptemys spp. in three river drainages and the importance of deadwood abundance Original Research Article

Eight replicated spotting-scope surveys of basking turtles and deadwood were conducted in the Pearl and Pascagoula river drainages in Mississippi and Louisiana and the lower Tennessee River in Kentucky. Basking densities of two “narrow-headed” Graptemys, listed as Threatened under the US Endangered Species Act and as Endangered by the International Union for the Conservation of Nature, were 2.3 per 100 m of riverbank for G. oculifera in the Pearl drainage, and 0.8 per 100 m for G. flavimaculata in the Pascagoula drainage. Density of G. flavimaculata met threshold values established for delisting at three of 16 sites. Density of the unlisted narrow-headed G. ouachitensis in the Tennessee drainage was 2.9 turtles per 100 m of shoreline. Density of an unlisted “broad-headed” species, G. gibbonsi, was 5.1 times lower than density of the two sympatric listed species in the Pearl and Pascagoula drainages and the broad-headed species G. pseudogeographica kohnii from the Tennessee drainage. Graptemys gibbonsi was only recently described and should be considered for listing. Correlations of Graptemys or total turtle density with deadwood density were positive in all cases and significant in five of nine analyses, and high basking densities were never associated with low deadwood densities. Removal of deadwood from rivers is thus probably detrimental to Graptemys populations.