A common characteristic of reptiles is their cold-blooded metabolism, meaning that their internal body temperature is regulated by external environmental conditions. Reptiles, such as snakes, lizards, and turtles, rely on the sun and warm surfaces to increase their body temperature for optimal metabolic function. This physiological trait allows them to conserve energy, as they do not need to maintain a constant body temperature through metabolic heat production like warm-blooded animals. Additionally, reptiles are characterized by scales or scutes that protect their skin from desiccation and environmental hazards.