Life History and Ecology of the Pascagoula Map Turtle (\u3ci\u3eGraptemys gibbonsi\u3c/i\u3e)

Abstract

Graptemys gibbonsi Lovich and McCoy (Pascagoula Map Turtle) is one of the most poorly understood turtle species in North America. Following the description of the species in 1992, little formal research has been conducted on the species other than population survey work. From 2005 to 2008, we conducted ecological studies on G. gibbonsi throughout the Pascagoula River ssytem of southeastern Mississippi, USA. We captured turtles at four sites to determine population structure, growth, movements, and some aspects of reproductionand nesting. We studied a single population to examine basking ecology and diet. We used visual surveys at four sites to document population density and relative abundance. Body size varied significatnly across sites and population-level sexual size dimorphism also varied. Growth was relatively rapid in small adults, with growth being slower in larger adults. Mean minimum linear active areas were in the spring and fall relative to summer, while also being longer during morning and evening periods; females generally based on larger, more robust logs versus smaller brances chosen by males. Graptemys gibbonsi basked at lower percentages (12% less) across seasons and throughout the day relative to the sympatric G. flavimaculata. Population densities and relative abundances of G. gibbonsi were greater at middle and upstream localities compared to downstream sections of the Pascagoula River system. Diet of males (n = 8) consisted primarily of caddisfly larvae and insect fragments, while females (n =4) consumed mostly Asian clams (Corbicula spp.) Reproduction extended from April to July for females \u3e 15.4 cm plastron length, with nests (n=3) encountered on both sandbars and cutbanks