The most widely distributed land mammal is the brown rat, also known as the Norway rat. Originating from Central Asia, brown rats have adapted to various environments and can thrive in urban, suburban, and rural settings worldwide. They are notorious for their ability to reproduce rapidly and have established populations in nearly every country. Their adaptability and resourcefulness contribute to their success as a species. Although often considered pests, brown rats play significant roles in ecosystems and scientific research, particularly in studies related to behavior and disease.