Maturational changes in male slider turtles (Trachemys scripta) from Illinois.

Accurate identification of sexually mature individuals is essential for life-history studies. In emydid turtles, secondary sexual characters (SSCs) are most often used to identify male maturity while numerous other methods exist. In this study, we examined the association between body size, age, foreclaw length (FCL), preanal tail length (PTL), testis mass, and plasma androgen level in Slider Turtles (Trachemys scripta; n = 40) from multiple populations in Illinois. We determined the accuracy of these methods by dissecting male Slider Turtles and used the presence of sperm as a definitive test of sexual maturity. Male T. scripta matured at 98 mm plastron length, between 3-5 years old, and generally had FCLs 7 mm, PTLs 13 mm, and testis weights 0.06 g. Androgen levels were significantly higher in mature males compared to immature males and immature females. Overlap in the individual raw values for androgens between categories limits their use for identifying maturity in this species. Overall, size and SSCs appear to be the least invasive and most accurate methods available to identify male maturity.