Observations on the Life Histories of Turtles (Genus Pseudemys and Graptemys) in Lake Texoma, Oklahoma

Abstract

Aspects of the life histories of Pseudemys scripta elegans and Graptemys pseudogeographica ouachitensis (Reptilia: Testudines) were studied in Lake Texoma, Oklahoma. Variation in the color patterns of the two species is considered. Males of Pseudemys are sexually mature at a plastron length of 9.0 to 10.0 cm; females at 17.4 to 19.3 The realized annual reproductive capacity of a female Pseudemys is estimated to be 26.4 eggs (3 clutches; 8.8 eggs per clutch). Some males become sexually mature in their third year; females in their fourth. Males of Graptemys are sexually mature at a plastron length of 7.0 cm; females at 15.0 cm. Each Graptemys female lays approximately 19.5 eggs per year (3 clutches; 6.5 eggs per clutch). The elongation of the tail and third claw of the forelimb are secondary sexual characters in males of both species. Growth in both species progresses rapidly prior to maturity, however, Graptemys females seemingly grow more slowly than Pseudemys during this period. Rapid fluctuation of the water level may result in a slowing of growth in Pseudemys, but the evidence is only suggestive, not conclusive. Alternation of habitats along the shoreline due to the changing water level is believed to be responsible for the nomadic behavior of Pseudemys as well as in determining the quality and quantity of food available. The abundance of the red-eared turtle, Pseudemys scripta elegans Wied, and the Ouachita map turtle, Graptemys pseudogeographica ouachitensis Cagle, in Lake Texoma, made possible a comparative life history study at the University of Oklahoma Biological Station, Marshall County, 2 miles east of Willis. Acknowledgments.-I am grateful to Dr. Carl D. Riggs, Director of the Biological Station for permission to utilize facilities in his care. I am indebted further to Dr. Harley P. Brown of the University of Oklahoma Department of Zoology for the analysis of the animal material in the contents of digestive tracts of selected turtles, and to Dr. George J. Goodman of the University of Oklahoma Department of Botany for selected botanical determinations. Finally, thanks are extended to Drs. Fred R. Cagle and Henry S. Fitch for constructive criticism of the manuscript.