Meeting Abstract
Sexual-dimorphism is a common trait in animals. Usually through the use of hormones, males and females of the same species can differ greatly in size, coloration, and behavior. In lizards, sexually-dimorphic color signals are used extensively during mate-selection. During mating season male bearded dragons will darken their “beard”, the underside of the mandible, as a territorial or confrontational display. Bearded dragons have another color patch on its dorsum that is believed to be hormonally controlled, but is not sexually-selected for. In this study, we will measure how pharmaceutical dosages of Testosterone and Corticosterone, both individually and through their interaction, effect these color patches in male Bearded Dragons. Hormone packets containing supranatural amounts of the respective hormones will be surgically inserted into the lizard’s abdominal cavity. This will artificially increase the animals’ hormone levels above natural levels, forcing a response if one exists. We will then be comparing the animal’s color expression to its circulating hormone levels. Color expression and reflectance data will be measured weekly using digital photography and guidelines set by Stevens et al., 2007. Circulating hormone levels will be determined by a weekly blood draw, and ELISA for testosterone, corticosterone, and estradiol. Testosterone is expected to have a darkening effect on the “beard”, but little to no effect on the dorsal color patch. Corticosterone is expected to decrease the melanization of the “beard”, but increase the melanization of the dorsum.
