Predicted Sex Ratio of Juvenile Kemp's Ridley Sea Turtles Captured near Steinhatchee, Florida

The Kemp's Ridley (Lepidochelys kempii) is one of the most endangered sea turtles in the world, and it possesses temperature-dependent sex determination (TSD). Sex ratios produced under TSD can vary widely and can affect the reproductive ecology of a population. Therefore, sex ratios produced from TSD are of ecological and conservation interest. The current study validated and utilized a testosterone radioimmunoassay (RIA) to examine the sex ratio of juvenile Kemp's Ridleys inhabiting the waters near Steinhatchee, Florida. Testosterone levels were measured in blood samples collected from juvenile Kemp's Ridleys captured over a three-year period. Results of this study indicate that a significant female bias (approximately 3.7:1) occurs in the aggregation of juvenile Kemp's Ridleys inhabiting the waters near Steinhatchee.

Fig. 1.

Serum testosterone levels of juvenile Kemp's Ridley Sea Turtles whose sex was verified by laparoscopic examination (Coyne and Owens, unpubl. data). Each bar, in order of increasing testosterone concentration, represents an individual turtle.

Fig. 2.

Serum testosterone levels and predicted sex of juvenile Kemp's Ridley Sea Turtles that were captured foraging near Steinhatchee, Fl. Each bar, in order of increasing testosterone concentration, represents an individual juvenile.

Fig. 3.

Sex ratios of Kemp's Ridley Sea Turtles grouped by size using ten cm intervals. The ratios for 20–29.9 cm group (6.0:1.0, female:male) and 30–39.9 cm group (5.6:1.0, female:male) of turtles are significantly female biased (P < 0.005), while the sex ratio of the 40–49.9 cm group (1.0:1.3, female:male) is unbiased (P > 0.05). One turtle was excluded from analysis because the size was not available to the author

Contributor Notes

(AAG, TW) Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, Alabama 35294-1170; (WJB) USGS Florida Integrated Science Centers, 7920 NW 71st Street, Gainesville, Florida 32653-3701; (MC) National Ocean Service, 1305 East-West Highway, SSMC4, Room 9257, Silver Spring, Maryland 20910; (AML) Texas A&M University Galveston, Galveston, Texas 77553; (DO) Grice Marine Laboratory, 205 Fort Johnson Road, Charleston, South Carolina 29412. (TW) twibbels@uab.edu Send reprint requests to TW.

Accepted: 22 Nov 2004