Humans aren't the only mammal that is homeothermic. There are several other mammals that are homeothermic as well. When we say homeothermic, we mean that they are able to sustain a constant body temperature regardless of the wide range of environment temperatures. Although, it's impacted within time-to-time. They are able to maintain a steady body temperature, regardless of external temperatures. If you have any questions, ask me! I hope I helped you.