Seasonal Patterns of Plasma Testosterone Levels, Bite Force, and Locomotor Performance in Non-Territorial Male Lizards, Aspidoscelis Sexlineata

The ability to perform key behaviors associated with reproduction, such as biting and locomotion in male lizards, has been linked to social dominance and reproductive success. The underlying mechanisms that govern variation in performance capacity, however, remain unclear. The steroid hormone testosterone mediates numerous traits associated with reproduction in male vertebrates and has been hypothesized to mediate variation in performance. This study examined seasonal patterns of circulating testosterone, morphology, bite force, and locomotor performance in a non-territorial lizard species to address this hypothesis. Male Aspidoscelis sexlineata (n=133) were collected throughout the active season, and testosterone levels and performance capacities were measured. Performance capacities were greatest during the breeding season when testosterone levels were elevated. The results of this study support the hypothesis that testosterone levels are related to variation in performance and suggest that seasonal changes in testosterone and performance are timed in a way to maximize reproductive success