Environmental Influence on the Male Reproductive Physiology of the Garden Lizard (Calotes Versicolor)

Reptilian reproductive physiology is intimately linked with external environmental conditions. Unlike homeothermic vertebrates, reptiles are ectothermic, and their biological processes are deeply dependent on climatic and ecological variables. Among these processes, reproduction represents one of the most environmentally sensitive functions. The garden lizard (Calotes versicolor), a widely distributed agamid species in South and Southeast Asia, offers a valuable model for investigating how environmental cues regulate reproductive activity in tropical reptiles. This paper examines the seasonal reproductive physiology of male C. versicolor with particular attention to testicular morphology, spermatogenic activity, and secondary sexual characteristics. The study integrates histological observations of naturally deceased specimens with non-invasive hormone assessment using fecal steroid metabolite profiling. Observational ecological data on temperature, photoperiod, humidity, and rainfall were analyzed in relation to reproductive patterns. Results indicate that temperature and photoperiod serve as the most powerful proximate regulators of testicular activity, while rainfall acts indirectly by influencing prey availability and habitat productivity. Testes undergo clear seasonal cycles: enlargement with active spermatogenesis in pre-monsoon months, partial regression during monsoon, and complete regression in post-monsoon winter. Fecal testosterone levels mirrored these histological changes. The findings highlight the fine-tuned synchrony between male reproductive cycles and the monsoonal environment, ensuring reproductive readiness when ecological conditions favor offspring survival. The study also underscores the utility of non-invasive hormone monitoring in reptiles, presenting an ethically sound approach for future ecological endocrinology. Keywords: Calotes versicolor, reproductive cycle, spermatogenesis, photoperiod, environment, histology, non-invasive endocrinology