C-Fos, an early intermediate gene, is a protein that can be used as an indicator of genetic mechanisms in neurons. Studies in many vertebrates have linked the production of C-Fos to the regulation of courtship and mating behavior. However, little is known about these proteins in relation to reptilian behavior. In our study, C-Fos expression was observed in the brains of male Red-Sided Garter snakes following exposure to the female sex attractant pheromone at different intervals ranging from 0 minutes to 45 minutes revealing a specific window of activation.