Historical turtle population decline and community changes in an Ozark River

Abstract

Turtle populations are declining worldwide yet few long term studies exist to confirm this trend. Mark-recapture data collected in 1969 and 1980 exist for the turtle community inhabiting a 4.6 km section of the North Fork of White River, Ozark County, Missouri. Using the available data, we compared the turtle communities and common map turtle (Graptemys geographica) populations observed in the research section in 1969 and 1980. Community composition changes indicated that red-eared sliders (Trachemys scripta elegans), a native species that was not observed in the research section in 1969, became established in the research section by 1980. Population estimates for G. geographica indicated that the population declined significantly (N1969 = 274, N1980 = 139, z = 3.39, P < 0.001) between 1969 and 1980 and the decline was associated with a marked decrease in the number of large adult females. The loss of large adult female G. geographica suggested the decline may have been a result of targeted harvest for the food trade as females of this species attain much larger body sizes and would therefore be preferred for the food trade. The results of this study elucidate changes that occurred in a turtle community and provide a historical baseline for comparison with future studies of this community.