Currently all species of sea turtles are listed as threatened or endangered with extinction under the U.S. Endangered Species Act. In order to effectively construct management approaches we need as much information on various sea turtle populations as possible including demography, genetic origin, and critical habitat. One demographic piece of data that is lacking is the sex ratio of turtle populations in foraging habitats, as this information is integral in determining overall population abundance. Because secondary sex characteristics (i.e. males have longer tails) are not evident until turtles start to reach sexual maturity, the sex of juvenile turtles cannot be easily determined externally. The least invasive way to determine the sex of juvenile turtles is through hormone analysis (testosterone) of the blood plasma. There are several methods for determining hormone concentration in turtle plasma; we used enzyme-linked immunosorbent assays (ELISA), which are the most cost effective and user friendly technique available. The testosterone ELISA has recently been validated for use with green sea turtle Chelonia mydas plasma but has yet to be validated for the other sea turtle species. My project focused on the endangered Kemp’s ridley sea turtle Lepidochelys kempii that is only found in the Gulf of Mexico and U.S. Atlantic seaboard. We validated the ELISA testosterone technique through demonstrating ‘parallelism’ to prove that the assay is measuring the same antigen (i.e. testosterone) in the plasma extracts and the standard controls (provided in the testosterone assay kit). We then determined the sex of approximately 140 juvenile turtles
