Term of Award

Fall 2009

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.


Department of Biology

Committee Chair

Lance D. McBrayer

Committee Member 1

C. Ray Chandler

Committee Member 2

David C. Rostal


In territorial lizards, testosterone (T) has been suggested as a possible mediator of seasonal increases in endurance and bite force, which are important for maintaining territories and winning male-male competitions. Aspidoscelis sexlineata, a non-territorial lizard, has elevated bite force and endurance during the breeding season when T levels are elevated (Gowan 2008). Here, I investigated the effects of experimentally elevated T levels on bite force and endurance. Tonic-release implants elevated T levels for 2 weeks; however, they failed to increase performance during that time. Endurance decreased for all lizards in the lab study; suggesting that captivity negatively affects endurance. A second study was then conducted to examine the effects of training and T supplementation on locomotor performance in A. sexlineata. Training did not increase locomotor performance of male A. sexlineata; however, elevated T increased percent hematocrit. Ventral hue and testis volume decreased for all males in the second lab study, which may have been the result of chronic stress or the absence of environmental cues needed to induce or maintain breeding season condition. This study provides insight into the morphological and physiological traits under the influence of T in nonterritorial species.

Research Data and Supplementary Material