What makes it a reptile? There are numerous species and kinds of reptiles around the world. Indeed though there are numerous differences, reptiles do partake in many common traits. For starters, they use their lungs to breathe. but not as meliorated as mammals. Scales give protection from bloodsuckers, help retain water, and can play a part in courting and territorial clashes. Reptiles aren't the only creatures to have scales, but it's a common characteristic among all reptiles.