WACK, C.L.*; LOVERN, M.B.; Oklahoma State University: Sex, Age, and Season Effects on Plasma Steroids in Free-ranging Texas Horned Lizards

Although several studies exist on the ecology and reproductive behavior of Texas horned lizards (Phrynosoma cornutum), nothing is known about the underlying steroid concentrations that likely influence these ecological and reproductive traits. Due to its declining numbers, the Texas horned lizard is protected in several states, including Oklahoma; information on its physiology is therefore of critical interest. In the present study we collected small blood samples from the caudal vein and recorded basic demographic data in free-ranging adult and juvenile male and female lizards in central Oklahoma. Sampling occurred during the active period from April to October (horned lizards hibernate underground from about November until March). We will present data on plasma concentrations of the steroids testosterone, 17&beta-estradiol, progesterone, and corticosterone for all sex and age classes, analyzed by radioimmunoassay. We expect that these results will be interesting from a comparative perspective, given that horned lizards have an atypical life history compared to that of most other lizard species studied. Furthermore, we anticipate that this initial endocrine profile will serve as valuable information for other scientists to conduct further research on this species.